NASA's $11 billion plan to robotically bring rock samples from Mars back to Earth is too expensive and will take too long, the agency's administrator said Monday, so officials are tasking government and private sector engineers to come up with a better plan.

The agency's decision on how to move forward with the Mars Sample Return (MSR) program follows an independent review last year that found ballooning costs and delays threatened the mission's viability. The effort would likely cost NASA between $8 billion and $11 billion, and the launch would be delayed at least two years until 2030, with samples getting back to Earth a few years later, the review board concluded.

But that's not the whole story. Like all federal agencies, NASA faces new spending restrictions imposed by the Fiscal Responsibility Act, a bipartisan budget deal struck last year between the White House and congressional Republicans. With these new budget headwinds, NASA officials determined the agency's plan for Mars Sample Return would not get specimens from the red planet back to Earth until 2040.

One of the primary goals of NASA's Perseverance rover, driving around Mars since 2021, is to collect and catalog more than 30 samples of Martian rocket, sediment, and air for return to Earth by a future mission. Perseverance is sealing these specimens in cigar-size titanium tubes, and collectively, they will total roughly half a kilogram in mass.

Returning pristine specimens from Mars to Earth for analysis in ground-based labs has been a top priority for the planetary science community's decadal survey process. But getting those samples back has turned out to be a lot more challenging than NASA thought.

"The bottom line is that $11 billion is too expensive, and not returning samples until 2040 is unacceptably too long," NASA Administrator Bill Nelson told reporters Monday.

Getting in gear

So NASA is shaking up the Mars Sample Return program. The preexisting plan came together over the last seven years, with refinements from engineers at NASA's Jet Propulsion Laboratory, the institution charged with managing the effort.

The most recent iteration of the Mars Sample Return mission involves two launches. One would take place in 2030 with a European spacecraft that will orbit Mars and wait for the second mission—the responsibility of NASA—to depart Earth in 2035 with a Sample Retrieval Lander (SRL). The second launch would involve a Mars Ascent Vehicle (MAV), the rocket necessary to launch samples off the red planet and into space.

The lander would deliver the MAV to the Martian surface, and the Perseverance rover, already on Mars, will deliver sealed tubes of rock and soil specimens into a container for the trip back to Earth. The MAV would then launch the material into orbit around Mars, where the European-built Earth Return Orbiter would rendezvous with the sample container and pick it up for the journey home.

These launches were previously scheduled to occur two years apart in the late 2020s, but those target dates are no longer attainable with the current plan and budget, officials said Monday. Stretching out the two launches over a five-year span will spread out expenditures on the MSR program to fit within the agency's projected budget without "cannibalizing" NASA's other planetary science projects, like the Dragonfly mission to explore Saturn's moon Titan.

The most recent plan unveiled Monday would also remove two helicopters from the Sample Retrieval Lander. These helicopters, which could have picked up sample tubes and delivered them to the pod that would return them to Earth, were supposed to be based on NASA's Ingenuity helicopter successfully demonstrated on Mars with the Perseverance rover. Instead, the updated plan would rely entirely on Perseverance to hand off sample tubes to the Mars Ascent Vehicle.

There are also a few other changes to NASA's MSR architecture, including replacing solar arrays on the Sample Retrieval Lander with a nuclear power generator. This would improve the lander's reliability and provide better thermal conditions for the MAV, according to Sandra Connelly, deputy head of NASA's science mission directorate.

However, this architecture is pretty much dead on arrival.

"The current budget environment doesn’t allow us to pursue an $11 billion architecture, and 2040 is too long," Nelson said. "So what to do? I have asked our folks to reach out with a request for information to industry, to JPL, and to all NASA centers and to report back this fall an alternate plan that would get it back quicker and cheaper."

NASA's goal, according to Nelson, is to try to stay within a $5 billion to $7 billion range for the total cost of the MSR program, in line with a broad cost outline from the National Academies' planetary science decadal survey.

“I’m expecting to get everybody in high gear, and that we have the answers to this by this fall," Nelson said.

Asking for help

As soon as Tuesday, NASA will release a solicitation for the private sector to propose ideas to bring back Perseverance's samples. Companies with the best ideas will receive some NASA funding later this year to support 90-day studies, and these reports will inform agency leaders on how to proceed with the Mars Sample Return. NASA could be ready to make decisions on a new architecture by the end of the year.

“We are opening up the aperture and allowing industry to propose concepts," said Nicky Fox, head of NASA's science mission directorate. "Yes, we would be OK with a higher risk posture. I'm definitely looking at things that have high heritage, the kind of tried and true architectures and elements of architectures that maybe have worked in the past, different ways of doing the various elements, a smaller Mars Ascent Vehicle.”

The MAV is one of the most delicate pieces of the Mars Sample Return architecture. NASA's concept involves a two-stage solid-fueled rocket, developed by Lockheed Martin and Northrop Grumman, that would be delivered to the surface of Mars aboard the Sample Retrieval Lander, which is baselined to have more than twice the mass of NASA's Perseverance rover, currently the heaviest spacecraft to ever land on Mars.

Developing a lighter lander and a smaller rocket certainly wouldn't hurt, according to Doug McCuistion, former director of NASA’s Mars exploration program, who is now consulting the agency on the MSR program.

“Those are the drivers of mass and those are the drivers of cost and complexity, so it’s important to draw those down," he said.

At the same time as the industry studies, NASA leaders will ask engineers at JPL and other NASA centers for their own ideas. Fox said NASA hopes "out of the box" concepts will allow the agency to get the samples back to Earth in the 2030s. "This is definitely a very ambitious goal," she said. "We’re going to need to go after some very innovative new possibilities for a design, and certainly leave no stone unturned.”

There are several commercial companies that might have something to offer NASA.

Lockheed Martin is the only entity in the United States outside of NASA's Jet Propulsion Laboratory that has built a successful Mars lander. SpaceX's Starship rocket is designed to eventually land cargo and people on Mars. Theoretically, it could be used as a lander or an interplanetary transport for Mars Sample Return. NASA also has a roster of smaller US companies developing Moon landers that could be modified for landings on Mars.

Most likely, the architecture NASA ultimately chooses will mix and match various elements from industry, NASA centers, and the European Space Agency, which remains a committed partner on Mars Sample Return with the Earth Return Orbiter. Other options include returning the sample to the vicinity of the Moon, where a human mission or robotic spacecraft could pick up the Martian material for the final leg of the trip to Earth, according to Connelly.

"An industry partner, or centers, or JPL—this is totally arbitrary—they could propose using ERO (Earth Return Orbiter) and NASA’s MAV, but say, 'I’m going to create my own lander and my own CCRS (Capture, Containment, and Return System),'" Connelly said. "So there are different ways you can put these puzzle pieces together. They can create their own solution. There is no constraint on this."

Limits to Perseverance

Regardless of how this shakes out, Mars Sample Return will rival, and perhaps surpass, the James Webb Space Telescope as the most complex robotic space mission ever undertaken. The Sample Retrieval Lander will need to land more precisely on Mars than any prior mission in order to touch down near the Perseverance rover at Jezero Crater. Jezero was home to an ancient river delta and a lake the size of Lake Tahoe more than 3.5 billion years ago.

The robotic handoff from Perseverance to the sample container that will rocket back into space with the Mars Ascent Vehicle will also be a tricky effort. The launch of the MAV itself is also a first. No rocket has ever launched off of Mars and back into space. Then, at least under NASA's existing architecture, engineers must accomplish the first-ever rendezvous between two spacecraft in orbit around another planet. These are just a few of the challenges.

In response to a question from Ars, Fox said NASA does not envision actually requesting proposals for an end-to-end mission from industry or the science community. Instead, NASA will collect ideas from companies and NASA centers to inform changes to the government's overall design.

Then there's the question of what to do with the nuclear-powered Perseverance rover. Originally, Perseverance wasn't supposed to be part of the MSR architecture once it finished its job of collecting samples. NASA initially designed the follow-on mission to retrieve the samples with its own small rover to go out and pick up the sample tubes dropped on the ground by Perseverance. After axing the rover due to cost concerns, NASA added two helicopters to the retrieval mission. Now, officials have deleted those.

Perseverance is now critical for MSR. Under the updated MSR architecture, NASA would end Perseverance's mission of exploration in 2028 and drive the rover back to a parking spot in Jezero Crater to await landing of a retrieval spacecraft. At that time, Perseverance would "basically go into a quiescent mode until we can transfer the samples over for return to Earth," Connelly said.

NASA officials are optimistic Perseverance can survive long enough to do this job. The rover has ample power from its nuclear battery, and its sister rover, Curiosity, remains healthy on Mars nearly 12 years since landing.

Despite the setbacks, NASA continues to see Mars Sample Return as its top priority in planetary science. The agency is deferring preliminary work on the second-highest decadal priority, a robotic spacecraft to orbit Uranus, to move forward with MSR. China also plans to launch its own robotic mission to return samples from Mars around 2030.

“I think it’s fair to say that we are committed to retrieving the samples that are there, at least some of those samples," Nelson said.

Using sophisticated laboratories on Earth, scientists can learn more from Martian rock core samples and dust grains than they could with miniaturized labs carried aboard rovers operating in situ on the red planet. Researchers want to know whether life ever formed on Mars and what conditions on the planet were like billions of years ago.

“NASA does visionary science, and returning diverse, scientifically relevant samples from Mars is a key priority,” Fox said. "Our next steps will position us to bring this transformational mission forward and deliver revolutionary science from Mars—providing critical new insights into the origins and evolution of Mars, our solar system, and life on Earth.”

An L for JPL?

Until now, NASA's Mars Sample Return program has been managed by JPL, the lab in Southern California that runs most of the agency's deep space missions. JPL first took humanity into the Solar System with Voyager and explored Jupiter and Saturn with Galileo and Cassini. All of NASA's past Mars landing missions were managed by JPL.

But the legendary research lab, run by Caltech under contract from NASA, is in crisis. Apart from MSR's rising costs and delays, independent reviewers blamed JPL mismanagement for NASA's Psyche asteroid mission missing its 2022 launch window, a delay that cost taxpayers about $250 million.

Last year, NASA reduced spending on Mars Sample Return when deciding how to move forward with the program, prompting JPL to lay off 100 contractors. The workforce impacts escalated in February, when JPL said it would lay off about 530 employees, plus 40 additional contractors, or roughly 8 percent of its staff.

Fox said NASA will provide $310 million for the Mars Sample Return program in fiscal year 2024, which runs through September 30. This is less than one-third of the White House's original fiscal year 2024 budget request of $949 million. NASA said the White House's request for next year is $200 million. This money will pay for industry studies and will maintain some technology development efforts in areas likely to be utilized in the ultimate MSR architecture.

How much of that reduced funding will actually go to JPL? And will JPL need another round of layoffs? It's too early to say, Fox said. NASA is reshaping management of the entire Mars Sample Return program and elevating individual pieces of the architecture managed at different NASA centers, "instead of everything being under JPL," she said.

On top of the budget cuts, the agency's decision to cast a wide net for ideas on how to do Mars Sample Return is another hit for JPL, which could lose its decades-long grip on NASA's Mars program. Nelson issued a call for the lab to rise to the occasion.

"Right now, if JPL were to come up with the answer, then I’d say JPL is going to be sitting pretty good," he said. "But we’re opening this up to everyone because we want to get every new and fresh idea that we can.”

I’d wager a guess that we are, as a species, rather fond of our home planet (our wanton carbon emissions notwithstanding). But the ugly truth is that the Earth is doomed. Someday, the Sun will enter a stage that will make life impossible on the Earth’s surface and eventually reduce the planet to nothing more than a sad, lonely chunk of iron and nickel.

The good news is that if we really put our minds to it—and don’t worry, we’ll have hundreds of millions of years to plan—we can keep our home world hospitable, even long after our Sun goes haywire.

A waking nightmare

The Sun is slowly but inexorably getting brighter, hotter, and larger with time. Billions of years ago, when collections of molecules first began to dance together and call themselves alive, the Sun was roughly 20 percent dimmer than it is today. Even the dinosaurs knew a weaker, smaller star. And while the Sun is only halfway through the main hydrogen-burning phase of its life, with 4-billion-and-change years before it begins its death throes, the peculiar combination of temperature and brightness that make life possible on this little world of ours will erode in only a few hundred million years. A blink of an eye, astronomically speaking.

The Sun sows the seeds of its own demise through the basic physics of its existence. At this very moment, our star is chewing through something like 600 million metric tons of hydrogen every single second, slamming those atoms together in a nuclear inferno that reaches a temperature of over 27 million degrees Fahrenheit. Of that 600 million metric tons, 4 million are converted into energy— enough to illuminate the entire Solar System.

That fusion reaction is not perfectly clean, however. There is a leftover byproduct, an ash created by the nuclear fires: helium. That helium has nowhere to go, as the deep convection cycles that constantly churn material within the Sun don’t reach into the core where the helium is formed. So the helium sits there, inert, lifeless, useless—clogging up the machine.

At its present age, the Sun does not have high enough temperatures and pressures at its core to fuse helium. So, the helium gets in the way, increasing the overall mass of the core without giving it anything else to fuse. Thankfully, the Sun is easily able to compensate for this, and that compensation comes about through a bit of physics known as hydrostatic equilibrium.

The Sun exists in constant balance, living on the edge of a nuclear knife. On one side are the energies released by the fusion process, which, if left uncontrolled, could threaten to explode—or at the very least, expand—the Sun. Countering that is the immense gravitational weight of the star itself, pressing inward with all the might that 1,027 tons of hydrogen and helium can muster. If that force were to go unchecked, the Sun’s own gravity would crush our star into a black hole no bigger than a mid-sized city.

So what happens when an unstoppable force meets an irresistible pressure? Graceful balance—and a star that can live for billions of years. If, for some reason, the nuclear inferno randomly ratchets up in temperature, that will heat up the rest of the star and inflate its outer layers, easing the gravitational pressure and slowing down the nuclear reactions. And if the Sun were to randomly contract, more material would force itself into the core, where it would participate in the heady nuclear dance, and the release of energy that results would conspire to reinflate the star to normal proportions.

But the presence of helium ash, that nuclear trash, upsets that balance by displacing hydrogen that would otherwise fuse. The Sun can’t help but pull inward on itself—gravity is uncompromising and uncaring. And when it does, it forces the nuclear reactions of the core to increase in ferocity, raising its temperature, which in turn forces the surface of the Sun to swell and brighten.

Slowly, slowly, slowly, as helium continues to build up in the core of the Sun (or any other star of similar mass), it expands and brightens in response. It’s difficult to predict exactly when this brightening will result in calamity for our planet—that depends on a complex interplay of radiation, atmosphere, and ocean. But the general estimate is that we have roughly 500 million years left before life will become all but impossible.

The warming Sun will increase the Earth’s surface temperature. With higher temperatures, the oceans will evaporate. Since water vapor is an excellent greenhouse gas, more of it in the atmosphere will lead to even greater surface temperatures. Higher temperatures will force the oceans to evaporate even more, setting off a runaway cycle that will quickly see all of the Earth’s abundant surface water floating in our atmosphere.

Without water to lubricate tectonic activity, our plates will grind to a halt. Without tectonic activity to pull carbon from the atmosphere, our air will become chokingly thick. Within a hundred million years, we will become a twin of Venus, which experienced a similar fate billions of years ago—two worlds dead at the hands of their own stellar parent.

Planetary adjustment

The "habitable zone" is the region around a star where the temperatures can—in principle, at least—support liquid water on the surface of a planet. Close to the star, the temperatures are too high, and barring any exotic atmospheric contortions, water will be forced into its vapor form. Outside the range, it’s just too cold.

The Earth currently sits roughly in the middle of the Sun’s habitable zone, with Venus just on the inner edge and Mars almost outside of it. As the Sun ages, however, its increasing brightness will shift the zone ever further out into the Solar System.

If we want the Earth to survive the coming epochs, we’ll have to move it.

Moving an entire planet is no easy feat, as you might imagine. But thankfully, for once, we have the balance of astronomical timescales on our side. We don’t have to move the Earth today; we have hundreds of millions of years to plan our shift. And to do the trick, we can employ that same persistent force that keeps the planets in orbit around the Sun in the first place: gravity.

Our first task is to find a source of energy. Raising the Earth's orbit will require an enormous amount of energy, and the physics here is as clean as it is cruel: that energy has to come from somewhere. Thankfully, we can use Jupiter. Because it's 318 times more massive than the Earth, its simple motion through the heavens provides it with a stupendous amount of kinetic energy. Surely it won’t mind if we borrow some for ourselves.

Actually getting energy from Jupiter to the Earth will take a little bit of orbital chicanery. To help visualize what we’ll have to do, imagine standing on a rolling platform on some railroad tracks with a train barreling toward you. You can’t get off the tracks (because then this metaphor wouldn’t be any fun), so your only chance at survival is to go at least as fast as the train. Of course, if you simply let the train crash into you, you’ll then match its speed, but probably not in the way you would hope.

Instead, you reach into your pocket and pull out a trusty bouncy ball. Let’s imagine (again, to get this metaphor to work) that this is a perfect and indestructible bouncy ball. You launch the bouncy ball at the oncoming train. It bounces off the train. You catch it and start to roll forward, just a little bit. Repeating the exercise, you find through simple conservation of momentum that you’re able to steal some of the train’s energy and give it to yourself and your rolling platform. The train barely notices—it’s a train, after all—but you certainly do. If you get enough back-and-force done quickly enough, you’d find yourself smoothly moving down the tracks, avoiding disaster.

To return to our situation with the Earth and Jupiter, the metaphor works in the sense that we certainly want to avoid having Jupiter crash into our planet. But it breaks down because interplanetary bouncy balls aren’t exactly an option. So instead, we’ll have to resort to asteroids. We can send them on long orbits that loop around Jupiter, using their gravitational interactions to speed up the asteroid in exchange for a slight slowing of the giant planet’s motion. We can then return the asteroid to Earth, looping it in the opposite direction, slowing it down and giving us a boost.

The difference from a single pass will be barely measurable, let alone noticeable. It’s not like random floating space rocks can carry that much kinetic energy with them. But we just have to set it on repeat, looping over and over for hundreds of millions of years, nudging the Earth into ever higher orbits to escape the increasing ferocity of the Sun. If our descendants can manage it, it will keep our planet in the safe band of the habitable zone.

Stellar adjustment

If planetary rearrangement isn’t your bag, but you still have the capabilities to accomplish mega-engineering projects, I have another solution for you.

The main problem with the Sun is that helium is a natural byproduct of the fusion process that powers our star. The rate of hydrogen fusion is determined by the Sun's overall mass; bigger stars burn faster, and smaller stars burn slower. So if we want to limit the amount of helium production, we need to slow the fusion reactions. The most straightforward way to do that would be to decrease the Sun's overall mass.

Thankfully, the Sun is already doing that for us, just not fast enough. The surface of the Sun constantly emits a never-ending stream of tiny, charged particles, creating what we call the solar wind. In raw human-scale numbers, the amount of mass the Sun loses through the solar wind is incredible, roughly 1–2 million metric tons per second. All that fury adds up to one single Earth-mass every 150 million years.

We’re gonna need to bump that up a bit.

One way to do this is to simply heat up the Sun's surface, through lasers, particle beams, strong magnetic fields, or whatever mechanism our descendants choose. Heating up the surface would increase the amount of solar wind production, which would increase the rate of solar mass loss. But high-energy particles whizzing out of the Sun is generally counterproductive when it comes to keeping the Earth habitable, so the next challenge is to funnel those particles somewhere safe.

One way to do that is to create a series of particle accelerator stations in orbit around the Sun’s equator. They would constantly exchange charged particles, creating a ring of current as the Sun’s belt. That ring of current would create a toroidal (or, for the more Homeric physicists, donut-shaped) magnetic field, which would funnel the beefed up solar wind into polar outflows, out along the axis of rotation of the Sun and safely away from any planets.

That toroidal magnetic field could also be used to squeeze the star in a method known—and I’m not kidding about this—as the “huff-n-puff” technique. First you shut the stations down, allowing them to fall inward toward the Sun. Then you switch them on, allowing the magnetic field to halt and then reverse their descent. The close-in magnetic field squeezes on the equator of the Sun, forcing particles to eject out of the poles.

If our descendants are really industrious, they can capture the escaped solar wind and use it for other purposes, like systems of fusion reactors to power the whole enterprise. And if they’re really creative, they can just point the solar wind outflows in one direction, using them as a Sun-powered rocket to nudge our entire Solar System to new places within the Milky Way or even out of the galaxy entirely.

Of course, this “starlifting” technique makes the Sun less luminous; with less mass, the fusion reactions operate at a quieter pace, which lowers the intensity and size of our star. This would shift the habitable zone inward. We wouldn’t notice at first because our actions would counteract the natural tendency for the habitable zone to move outward. But eventually, after the Sun had lost more than 10 to 20 percent of its mass (the math is a bit imprecise because it depends on how long this siphoning procedure takes), we would be forced to migrate the Earth inward to maintain the sweet spot.

But we’d be left with a smaller star, and smaller stars live blissfully long lives. The smallest red dwarfs, with masses barely bigger than a tenth of the mass of the Sun, can burn for trillions of years. But they also tend to be temperamental. With their smaller mass, they’re more susceptible to raging fits of starbursts that can see their luminosities sporadically double. If our far-future descendants decide to embark on this path of modifying the Sun to increase its longevity, they will certainly have their work cut out for them to protect the fragile Earth.

But no matter what, if humanity is to survive all these billions of years, we will likely be an interplanetary, if not interstellar, species. There won’t be much need to rescue the Earth in this manner. Perhaps our far-future descendants will still put a plan into motion as an act of reverence to preserve the world that gave rise to them. Perhaps it will be out of necessity, as no other world will ever be as suitable for life as Earth. Perhaps it will be an art project, a chance to create beauty and wonder on an interplanetary scale, before the fires of fusion extinguish within the core of the Sun and it breathes its last, the final chapter of a story that contains the billions of years of life in this Solar System coming to a close.

As if we didn’t have enough reasons to get at least eight hours of sleep, there is now one more. Neurons are still active during sleep. We may not realize it, but the brain takes advantage of this recharging period to get rid of junk that was accumulating during waking hours.

Sleep is something like a soft reboot. We knew that slow brainwaves had something to do with restful sleep; researchers at the Washington University School of Medicine in St. Louis have now found out why. When we are awake, our neurons require energy to fuel complex tasks such as problem-solving and committing things to memory. The problem is that debris gets left behind after they consume these nutrients. As we sleep, neurons use these rhythmic waves to help move cerebrospinal fluid through brain tissue, carrying out metabolic waste in the process.

In other words, neurons need to take out the trash so it doesn’t accumulate and potentially contribute to neurodegenerative diseases. “Neurons serve as master organizers for brain clearance,” the WUSTL research team said in a study recently published in Nature.

Built-in garbage disposal

Human brains (and those of other higher organisms) evolved to have billions of neurons in the functional tissue, or parenchyma, of the brain, which is protected by the blood-brain barrier.

Everything these neurons do creates metabolic waste, often in the form of protein fragments. Other studies have found that these fragments may contribute to neurodegenerative diseases such as Alzheimer’s.

The brain has to dispose of its garbage somehow, and it does this through what’s called the glymphatic system (no, that’s not a typo), which carries cerebrospinal fluid that moves debris out of the parenchyma through channels located near blood vessels. However, that still left the questions: What actually powers the glymphatic system to do this—and how? The WUSTL team wanted to find out.

To see what told the glymphatic system to dump the trash, scientists performed experiments on mice, inserting probes into their brains and planting electrodes in the spaces between neurons. They then anesthetized the mice with ketamine to induce sleep.

Neurons fired strong, charged currents after the animals fell asleep. While brain waves under anesthesia were mostly long and slow, they induced corresponding waves of current in the cerebrospinal fluid. The fluid would then flow through the dura mater, the outer layer of tissue between the brain and the skull, taking the junk with it.

Just flush it

The scientists wanted to be sure that neurons really were the force that pushed the glymphatic system into action. To do that, they needed to genetically engineer the brains of some mice to nearly eliminate neuronal activity while they were asleep (though not to the point of brain death) while leaving the rest of the mice untouched for comparison.

In these engineered mice, the long, slow brain waves seen before were undetectable. As a result, the fluid was no longer pushed to carry metabolic waste out of the brain. This could only mean that neurons had to be active in order for the brain’s self-cleaning cycle to work.

Furthermore, the research team found that there were fluctuations in the brain waves of the un-engineered mice, with slightly faster waves thought to be targeted at the debris that was harder to remove (at least, this is what the researchers hypothesized). It is not unlike washing a plate and then needing to scrub slightly harder in places where there is especially stubborn residue.

The researchers also found out why previous experiments produced different results. Because the flushing out of cerebrospinal fluid that carries waste relies so heavily on neural activity, the type of anesthetic used mattered—anesthetics that inhibit neural activity can interfere with the results. Other earlier experiments worked poorly because of injuries caused by older and more invasive methods of implanting the monitoring hardware into brain tissues. This also disrupted neurons.

“The experimental methodologies we used here largely avoid acute damage to the brain parenchyma, thereby providing valuable strategies for further investigations into neural dynamics and brain clearance,” the team said in the same study.

Now that neurons are known to set the glymphatic system into motion, more attention can be directed towards the intricacies of that process. Finding out more about the buildup and cleaning of metabolic waste may contribute to our understanding of neurodegenerative diseases. It’s definitely something to think about before falling asleep.

Nature, 2024.  DOI: 10.1038/s41586-024-07108-6

Like many of the researchers who study how people find their way from place to place, David Uttal is a poor navigator. “When I was 13 years old, I got lost on a Boy Scout hike, and I was lost for two and a half days,” recalls the Northwestern University cognitive scientist. And he’s still bad at finding his way around.

The world is full of people like Uttal—and their opposites, the folks who always seem to know exactly where they are and how to get where they want to go. Scientists sometimes measure navigational ability by asking someone to point toward an out-of-sight location—or, more challenging, to imagine they are someplace else and point in the direction of a third location—and it’s immediately obvious that some people are better at it than others.

“People are never perfect, but they can be as accurate as single-digit degrees off, which is incredibly accurate,” says Nora Newcombe, a cognitive psychologist at Temple University who coauthored a look at how navigational ability develops in the 2022 Annual Review of Developmental Psychology. But others, when asked to indicate the target’s direction, seem to point at random. “They have literally no idea where it is.”

While it’s easy to show that people differ in navigational ability, it has proved much harder for scientists to explain why. There’s new excitement brewing in the navigation research world, though. By leveraging technologies such as virtual reality and GPS tracking, scientists have been able to watch hundreds, sometimes even millions, of people trying to find their way through complex spaces, and to measure how well they do. Though there’s still much to learn, the research suggests that to some extent, navigation skills are shaped by upbringing.

Nurturing navigation skills

The importance of a person’s environment is underscored by a recent look at the role of genetics in navigation. In 2020, Margherita Malanchini, a developmental psychologist at Queen Mary University of London, and her colleagues compared the performance of more than 2,600 identical and nonidentical twins as they navigated through a virtual environment to test whether navigational ability runs in families. It does, they found—but only modestly. Instead, the biggest contributor to people’s performance was what geneticists call the “nonshared environment”—that is, the unique experiences each person accumulates as their life unfolds. Good navigators, it appears, are mostly made, not born.

A remarkable, large-scale experiment led by Hugo Spiers, a cognitive neuroscientist at University College London, gave researchers a glimpse at how experience and other cultural factors might influence wayfinding skills. Spiers and his colleagues, in collaboration with the telecom company T-Mobile, developed a game for cellphones and tablets, Sea Hero Quest, in which players navigate by boat through a virtual environment to locate a series of checkpoints. The game app asked participants to provide basic demographic data, and nearly 4 million worldwide did so. (The app is no longer accepting new participants except by invitation of researchers.)

Through the app, the researchers were able to measure wayfinding ability by the total distance each player traveled to reach all the checkpoints. After completing some levels of the game, players also had to shoot a flare back toward their point of origin—a dead-reckoning test analogous to the pointing-to-out-of-sight-locations task. Then Spiers and his colleagues could compare players’ performance to the demographic data.

Several cultural factors were associated with wayfinding skills, they found. People from Nordic countries tended to be slightly better navigators, perhaps because the sport of orienteering, which combines cross-country running and navigation, is popular in those countries. Country folk did better, on average, than people from cities. And among city-dwellers, those from cities with more chaotic street networks such as those in the older parts of European cities did better than those from cities like Chicago, where the streets form a regular grid, perhaps because residents of grid cities don’t need to build such complex mental maps.

Results like these suggest that an individual’s life experience may be one of the biggest determinants of how well they navigate. Indeed, experience may even underlie one of the most consistent findings—and clichés—in navigation: that men tend to perform better than women. Turns out this gender gap is more a question of culture and experience than of innate ability.

Nordic countries, for example, where gender equality is greatest, show almost no gender difference in navigation. In contrast, men far outperform women in places where women face cultural restrictions on exploring their environment on their own, such as Middle Eastern countries.

This cultural aspect, and the importance of experience, are also supported by studies of the Tsimane, a traditional Indigenous community in the Bolivian Amazon. Anthropologist Helen Elizabeth Davis of Arizona State University and her colleagues put GPS trackers on 305 Tsimane adults to measure their daily movements over a three-day period, and found no difference in the distance moved by men and women. Men and women also were equally adept at pointing to out-of-sight locations, they reported in Topics in Cognitive Science. Even children performed extremely well at this navigation task—a result, Davis thinks, of growing up in a culture that encourages children to range widely and explore the forest.

Most cultures aren’t like the Tsimane, though, and women and girls tend to be more cautious about exploring, for good reasons of personal safety. Not only do they gather less experience at navigating, but nervousness about security or getting lost also has a direct effect on navigation. “Anxiety gets in the way of good navigation, so if you’re worried about your personal safety, you’re a poor navigator,” says Newcombe.

Personality, too, appears to play a role in developing navigational ability. “To get good at navigating, you have to be willing to explore,” says Uttal. “Some people do not enjoy the experience of wandering, and others enjoy it very much.”

Indeed, people who enjoy outdoor activities, such as hiking and biking, tend to have a better sense of direction, notes Mary Hegarty, a cognitive psychologist at the University of California, Santa Barbara. So do people who play a lot of video games, many of which involve exploring virtual spaces.

To Uttal, this accumulating evidence suggests that inclination and early experience nudge some people toward activities that involve navigation, while those who are temperamentally less inclined to explore, who have less opportunity to wander or who have an initial bad experience may be less likely to engage in activities that require exploration. It all snowballs from there, Uttal speculates. “I think a combination of personality and ability pushes you in certain directions. It’s a developmental cascade.”

Mental mappers

That cascade presumably influences the acquisition of the specific skills that are hallmarks of good navigators. These include the ability to estimate how far you’ve traveled, to read and remember maps (both printed and mental), to learn routes based on a sequence of landmarks, and to understand where points are relative to one another.

Much of the research, though, has focused on two specific subskills: route-following by using landmarks—for example, turn left at the gas station, then go three blocks and turn right just past the red house—and what’s often termed “survey knowledge,” the ability to build and consult a mental map of a place.

Of the two, route following is by far the easier task, and most people do pretty well at it once they’ve taken a route a few times, says Dan Montello, a geographer and psychologist also at UC Santa Barbara. In a classic experiment from almost two decades ago, Montello’s student Toru Ishikawa drove 24 volunteers, once a week for 10 weeks, on two twisting routes in a tony residential area of Santa Barbara that they’d never visited before.

Later, almost every person could accurately state the order of landmarks along each route and roughly estimate the distance travelled between them. But they varied widely in their ability to identify shortcuts between the two routes, point to landmarks not visible from where they stood, or sketch a map of the routes. Those who couldn’t identify shortcuts or find landmarks may suffer from an inability to create accurate mental maps, the researchers think.

Research by Newcombe and her then graduate student Steven Weisberg underscores the importance of such mental maps in navigation. They asked 294 volunteers to use a mouse and computer screen to navigate along two routes through a virtual town. Once the volunteers had learned the routes and the landmarks they contained, the researchers asked them to stand at one landmark and point to others on both routes.

People fell into three classes, the researchers reported in 2018 in Current Directions in Psychological Science. Some people had formed a good mental map: They could point accurately to landmarks on both the same and different routes. Others had good route knowledge but struggled to create an integrated map: They were good at pointing within a route, but poor between routes. A third group was poor at all the pointing tasks.

That ability to build and refer to a mental map—a person’s survey knowledge—goes a long way toward explaining why they’re better navigators, Montello says. “When the only skill you have is the ability to think in terms of routes, you can’t be creative to get around barriers.” Survey knowledge gives the ability to navigate creatively, he says. “That’s a pretty stunning difference.”

Not surprisingly, better navigators may also be better at switching modes and choosing the most appropriate navigational strategy for the situation they find themselves in, says cognitive neuroscientist Weisberg, now at the University of Florida. This could mean using landmarks when they are obvious and mental maps when more sophisticated calculations are needed.

“I’ve moved toward thinking that our better navigators are also using a lot of alternate strategies,” Weisberg says. “And they’re doing so in a much more flexible way that affords different kinds of navigation, so that when they find themselves in a new situation, they’re better able to find their way.”

When Weisberg moves around Gainesville where he lives now, for example, he keeps track of north, because that works well in a city with a regular street grid; when he goes home to the winding streets of Philadelphia, he relies more on other cues to stay oriented.

Researchers do not yet know whether every bad navigator is simply poor at survey knowledge, or whether some of the lost might be failing at other navigational subskills instead, such as remembering landmarks or estimating distance traveled. Either way, what can poor navigators do to improve? That’s still an open question. “We all have our pet theories,” says Elizabeth Chrastil, a cognitive neuroscientist at the University of California, Irvine, “but they haven’t reached the level of testing yet.”

Pros and cons of GPS

Simply practicing seems like it should work—and, indeed, it does in lab experiments. “We can improve people’s navigational abilities in virtual environments,” says Arne Ekstrom, a cognitive neuroscientist at the University of Arizona. It takes about two weeks to show fairly dramatic gains—but it’s not yet clear whether people are really becoming better navigators or just getting better at finding their way through the particular virtual environments used in the experiments.

Support for the notion that people might improve with practice also comes from studies of what happens when people stop using their navigation skills. In a 2020 study published in Scientific Reports, for example, neuroscientists Louisa Dahmani and Véronique Bohbot of McGill University in Montreal recruited 50 young adults and questioned them about their lifetime experience of driving with GPS. Then they tested the volunteers in a virtual world that required them to navigate without GPS. The heaviest GPS users did worse, they found.

A follow-up with 13 of the volunteers three years later revealed that those who had used GPS the most during the intervening period experienced greater declines in their ability to navigate without GPS, strongly suggesting that GPS reliance causes diminished skills, rather than poor skills leading to greater GPS use.

Experts also suggest that struggling navigators like Uttal could try paying closer attention to compass directions or prominent landmarks as a way to integrate their movements into a mental map. For Weisberg, the only way he learns spaces in an integrated way is by paying attention to major cardinal directions or prominent landmarks like the ocean. “The more attention I pay, the better I can link things to the map in my head.” He recommends that struggling navigators ask themselves which way is north 10 times a day, referring to a map if necessary. This, he suggests, could help them move beyond mere route knowledge.

There’s another option for those who don’t really care about improving their skills as long as they just don’t get lost, Weisberg notes: Just make sure your GPS is handy.

This article originally appeared in Knowable Magazine, a nonprofit publication dedicated to making scientific knowledge accessible to all. Sign up for Knowable Magazine’s newsletter.

Glistening in the dry expanses of the Nevada desert is an unusual kind of power plant that harnesses energy not from the sun or wind, but from the Earth itself.

Known as Project Red, it pumps water thousands of feet into the ground, down where rocks are hot enough to roast a turkey. Around the clock, the plant sucks the heated water back up to power generators. Since last November, this carbon-free, Earth-borne power has been flowing onto a local grid in Nevada.

Geothermal energy, though it’s continuously radiating from Earth’s super-hot core, has long been a relatively niche source of electricity, largely limited to volcanic regions like Iceland where hot springs bubble from the ground. But geothermal enthusiasts have dreamed of sourcing Earth power in places without such specific geological conditions—like Project Red’s Nevada site, developed by energy startup Fervo Energy.

Such next-generation geothermal systems have been in the works for decades, but they’ve proved expensive and technologically difficult, and have sometimes even triggered earthquakes. Some experts hope that newer efforts like Project Red may now, finally, signal a turning point, by leveraging techniques that were honed in oil and gas extraction to improve reliability and cost-efficiency.

The advances have garnered hopes that with enough time and money, geothermal power—which currently generates less than 1 percent of the world’s electricity, and 0.4 percent of electricity in the United States—could become a mainstream energy source. Some posit that geothermal could be a valuable tool in transitioning the energy system off of fossil fuels, because it can provide a continuous backup to intermittent energy sources like solar and wind. “It’s been, to me, the most promising energy source for a long time,” says energy engineer Roland Horne of Stanford University. “But now that we’re moving towards a carbon-free grid, geothermal is very important.”

A rocky start

Geothermal energy works best with two things: heat, plus rock that is permeable enough to carry water. In places where molten rock sizzles close to the surface, water will seep through porous volcanic rock, warm up and bubble upward as hot water, steam, or both.

If the water or steam is hot enough—ideally at least around 300 degrees Fahrenheit—it can be extracted from the ground and used to power generators for electricity. In Kenya, nearly 50 percent of electricity generated comes from geothermal. Iceland gets 25 percent of its electricity from this source, while New Zealand gets about 18 percent and the state of California, 6 percent.

Some natural geothermal resources are still untapped, such as in the western United States, says geologist Ann Robertson-Tait, president of GeothermEx, a geothermal energy consulting division at the oilfield services company SLB. But by and large, we’re running out of natural, high-quality geothermal resources, pushing experts to consider ways of extracting geothermal energy from areas where the energy is much harder to access. “There’s so much heat in the Earth,” Robertson-Tait says. But, she adds, “much of it is locked inside rock that isn’t permeable.”

Tapping that heat requires deep drilling and creating cracks in these non-volcanic, dense rocks to allow water to flow through them. Since 1970, engineers have been developing “enhanced geothermal systems” (EGS) that do just that, applying methods similar to the hydraulic fracturing—or fracking—used to suck oil and gas out of deep rocks. Water is pumped at high pressure into wells, up to several miles deep, to blast cracks into the rocks. The cracked rock and water create an underground radiator where water heats before rising to the surface through a second well. Dozens of such EGS installations have been built in the United States, Europe, Australia, and Japan—most of them experimental and government-funded—with mixed success.

Famously, one EGS plant in South Korea was abruptly shuttered in 2017 after having probably caused a 5.5-magnitude earthquake; fracking of any kind can add pressure to nearby tectonic faults. Other issues were technological—some plants didn’t create enough fractures for good heat exchange, or fractures traveled in the wrong direction and failed to connect the two wells.

Some efforts, however, turned into viable power plants, including several German and French systems built between 1987 and 2012 in the Rhine Valley. There, engineers made use of existing fractures in the rock.

But overall, there just hasn’t been enough interest to develop EGS into a more reliable and lucrative technology, says geophysicist Dimitra Teza of the energy research institute Fraunhofer IEG in Karlsruhe, Germany, who helped develop some of the Rhine Valley EGS systems. “It has been quite tough for the industry.”

New momentum

Solutions exist for both safety and technological problems. There are, in fact, robust protocols for avoiding earthquakes, such as by not drilling near active faults. Long-term monitoring of the operating EGS plants in France and Germany has documented only minor tremors, building confidence in the safety of the technology. Importantly, drilling and fracking methodology has improved by leaps and bounds, thanks to the boom in oil and gas extraction from shale rocks that began in the 2010s. “Since then, we’ve seen a renewed interest in EGS as a concept, because the techniques that are central to EGS were perfected and brought down significantly in cost during that time,” says Wilson Ricks, an energy systems researcher at Princeton University.

In 2015, for instance, the US Department of Energy launched a research site in Utah dedicated to advancing EGS technologies. Several new North American startups, including Sage Geosystems and E2E Energy Solutions, are developing new EGS systems in Texas and Canada, respectively. The most advanced is Fervo Energy, which has applied several techniques from the shale industry at its Nevada plant, which now supplies a local grid that includes energy-sucking data storage centers owned by Google. (Google partnered with Fervo to develop the plant.)

Engineers drilled almost 8,000 feet downward into the Nevada rock, reaching temperatures of nearly 380 degrees Fahrenheit, and then, at the bottom, drilled another 3,250-foot horizontal well to expand the area of hot rock that the system touches—a technique used in oil and gas extraction in order to maximize yield. The company also fractured the surrounding rock at several sites along the horizontal well to create a more extensive web of cracks for water to trickle through. Technologically speaking, compared to earlier EGS efforts, “they are, in fact, a big step forward,” says Horne, who is on Fervo’s scientific advisory board.

It remains to be seen how these new EGS systems perform in the long term. One advantage of systems like Fervo’s is that they can be made more profitable by taking advantage of energy price fluctuations, according to recent research by Ricks, a Princeton colleague and several experts at Fervo Energy. Operators could plug the exit wells, causing water to accumulate inside the system, building up pressure and heat. Then the energy could be extracted during times when it is most valuable—such as during cloudy or windless periods when solar or wind aren’t working.

Still, such systems would have to be significantly scaled up to be commercially viable, Ricks says. Although Project Red claims a larger capacity than any other EGS plant—3.5 megawatts, enough to power more than 2,500 homes—it’s still relatively small; a nuclear or coal plant can easily have an output of 1,000 megawatts, while large solar or traditional geothermal plants often produce several hundred megawatts.

What the EGS field needs right now, Ricks says, is the funding to build and test more such systems to inspire investor confidence. “This all needs to be very well proven, out to the point where the perceived risk is low,” he says.

A turning point for geothermal?

To that end, the US Department of Energy recently awarded $60 million in funding to three demonstration projects for EGS and related technologies as part of a broader initiative to speed up EGS development. One 2019 report from the agency estimated that, with advances in EGS, geothermal power could represent around 60 gigawatts (60,000 megawatts) of installed capacity in the United States by 2050, generating 8.5 percent of the country’s electricity—a more-than-20-fold increase from today.

Even an increase of a few percent could aid in a global energy transition that’s aiming to get to net zero carbon emissions by 2050. “If in fifteen, twenty years, EGS is viable, I think it could play a huge part,” says Nils Angliviel de La Beaumelle, who recently coauthored an article on the global outlook for renewable energy in the Annual Review of Environment and Resources.

Other geothermal technologies may also help. Some companies are exploring the feasibility of “super hot rock” geothermal—essentially, a young, extreme variant of EGS that involves drilling down even deeper into Earth’s crust, to a depth where water reaches a “supercritical” vapor-like state that allows it to carry much more energy than either steam or liquid. In southern Germany, the energy company Eavor is building the world’s first “closed-loop” geothermal system: Once pipes funnel water into the deep rock, the system fans out into a network of parallel boreholes, without water ever penetrating the rock. That’s a more predictable—albeit less efficient—way of warming water, as it doesn’t involve uncertainties around fracturing the rock in the right way, Teza says. “I’m really excited to see that there’s investment into these technologies,” she says. “I think it can only help.”

On the whole, it’s an important moment for geothermal energy—and not just for providing carbon-free electricity, Robertson-Tait says. Geothermal brines hauled out of the Earth are rich in lithium and other critical minerals that can be used to build green technologies like solar panels and EV batteries. There’s a growing push to use direct geothermal heat to warm buildings, either through shallow heat pumps for residential buildings or larger systems designed for entire districts—like Paris and Munich already have.

Some oil and gas companies, recognizing that a change is coming, are increasingly interested in building geothermal systems of various kinds, says Robertson-Tait. “Our Earth is geothermal,” she says, “and so I think we owe it to ourselves to do everything we can to use it.”

This article originally appeared in Knowable Magazine, a nonprofit publication dedicated to making scientific knowledge accessible to all. Sign up for Knowable Magazine’s newsletter.

Welcome to Edition 6.39 of the Rocket Report! The big news this week came from United Launch Alliance, and the final mission of its Delta IV Heavy rocket. Both Stephen and I had thoughts about this launch, which is bittersweet, and we expressed them in stories linked below. It's been a little less than 20 years since this big rocket debuted, and interesting to think how very much the launch industry has changed since then.

As always, we welcome reader submissions, and if you don't want to miss an issue, please subscribe using the box below (the form will not appear on AMP-enabled versions of the site). Each report will include information on small-, medium-, and heavy-lift rockets as well as a quick look ahead at the next three launches on the calendar.

Rocket Lab to reuse flight tank. On Wednesday Rocket Lab said it is returning a previously flown Electron rocket first stage tank to the production line for the first time in preparation for reflying the stage. The company characterized this as a "significant" milestone as it seeks to make Electron the world's first reusable small rocket. This stage was successfully launched and recovered as part of the ‘Four of a Kind’ mission earlier this year on January 31.

Iterating a path to reuse ... The stage will now undergo final fit out and rigorous qualification for reuse. "Our key priority in pushing this stage back into the standard production flow for the first time is to ensure our systems and qualification processes are fit for accepting pre-flown boosters at scale," said Rocket Lab founder and CEO Peter Beck. "If this stage successfully passes and is accepted for flight, we’ll consider opportunities for reflying it in the new year.” (submitted by Ken the Bin)

Virgin Orbit IP for sale on LinkedIn. In a post this week on the social networking site LinkedIn, former Virgin Orbit chief executive Dan Hart said that the Virgin Orbit IP library is being made available for licensing. "The flight-proven LauncherOne IP can accelerate launch and hypersonic system development schedules by years, and enable significant cost savings," Hart wrote. "The innovative designs can also offer component/subsystem providers immediate product line expansion."

Yours for a low, low price ... The IP library includes all manner of goodies, including an FAA-approved flight termination system, the Newton 3 and Newton 4 engines, avionics, structures, and more. Price for access to all IP is $3 million for a nonexclusive license, Hart said. I have no idea whether that's a good price or not.

Virgin Galactic countersues Boeing. Virgin Galactic has filed a countersuit against Boeing over a project to develop a new mothership aircraft, arguing in part that Boeing performed poorly, Space News reports. The suit, filed last week in the US District Court for the Central District of California, comes two weeks after Boeing filed suit against Virgin Galactic, alleging that Virgin refused to pay more than $25 million in invoices on the project and misappropriated trade secrets.

Citing Boeing's own record ... The dispute revolves around a project announced in 2022 to develop a new aircraft that would replace Virgin’s existing VMS Eve as an air-launch platform. Virgin, in its suit, claims that Boeing performed “shoddy and incomplete” work on the initial phases of the project. “Boeing’s failures with respect to its agreement with Virgin Galactic are consistent with Boeing’s record of poor quality control and mismanagement,” the complaint states. (submitted by EllPeaTea)

Navy awards contract to Ursa Major. The rocket propulsion startup said Monday it has signed a contract with the United States Navy to develop and test solid fuel rocket engines in an effort to develop a next generation of solid rocket motor for the Navy's standard missile program, Reuters reports. The agreement is part of a series of prototype engine contracts being awarded by the US Navy as it seeks to expand the industrial base for manufacturing them.

Broadening the US supplier base ... The deal comes as the Navy is seeing a surge in missile demand due to the ongoing conflicts in Gaza and Yemen and the war in Ukraine. "Our new approach to manufacturing solid rocket motors allows Ursa Major to quickly develop high-performing motors at scale, driving volume and cost efficiencies to address this critical national need," said Ursa Major Founder Joe Laurienti. (submitted by Ken the Bin)

Ariane 6 debut may not be totally successful. Speaking during the Space Symposium this week, European Space Agency Director General Josef Aschbacher sought to temper expectations for the debut launch of the Ariane 6 rocket this summer. He explained that the debut flights of larger rockets have a 47 percent chance of experiencing a major anomaly, European Spaceflight reports.

Really can't afford to fail ... While Aschbacher is certainly correct that large rockets have a mixed record in their debuts, the Ariane 6 program has some major advantages. Its first and second stages both have elements of heritage hardware, and the P120C boosters have flown before. Moreover, as the product of a decade-long development program, with a large budget, it would be a major disappointment if Ariane 6 did not complete its first mission. (submitted by EllPeaTea)

Digital age coming to US launch ranges. After years of kicking the can down the road on modernization, the US Space Force is now embarking on a comprehensive overhaul of the IT infrastructure used at mission control centers at Cape Canaveral Space Force Station in Florida and Vandenberg Space Force Base in California, Space News reports. "At Vandenberg, a lot of the infrastructure that’s there was put in place for the Space Shuttle. That’s how old it is," said retired US Air Force Col. Chad Davis, former director of the National Reconnaissance Office’s Office of Space Launch. "They’ve been Band-Aiding it through the years but have never really done any significant overhaul."

Catching up to high cadence ... The digital transformation is intended to enable high operational tempos. With commercial space companies like SpaceX rapidly driving up the launch cadence, these upgrades are long overdue, said Maj. Jason Lowry, deputy director of technology and innovation at the Space Systems Command’s Assured Access to Space program office. "We’re expanding very fast and we’re still using systems that were designed to support single digit launches per year, not triple digit launches per year," he said at a forum hosted by SpaceWERX, the Space Force’s technology arm. (submitted by Ken the Bin)

FAA has no plans to tax launch. A Federal Aviation Administration official said Wednesday that the Biden administration has no plans for the time being to levy taxes on commercial launches, similar to those on airlines, to address the launch industry’s impact on airspace, Space News reports. The Biden administration has previously broached the idea by saying that launch companies were getting a “tax-free ride” by not funding the FAA’s air traffic management work even as launches impose temporary airspace closures that affect aviation.

Still a ways to go ... However Kelvin Coleman, FAA associate administrator for commercial space transportation, said that there are no current plans to seek a tax on commercial launches. "At this point, there is no concrete proposal in the president’s budget request," he said at the Space Symposium conference. "There are conversations, there’s things we talked about, but I think there’s still a ways to go before we see something concrete in that regard." The commercial launch industry privately reacted to the report about the tax proposal with surprise and dismay. (submitted by Jay500001)

SpaceX launches new line of rideshare missions. SpaceX launched the first in a new class of dedicated rideshare missions on Sunday, delivering 11 commercial and military satellites into mid-inclination orbits, Space News reports. Unlike SpaceX's existing Transporter missions, which launch payloads into Sun-synchronous orbits commonly used by remote-sensing satellites, the new Bandwagon missions are intended to send payloads to low-Earth orbits at inclinations of about 45 degrees.

Demand is high ... Bandwagon-1 carried 11 satellites, with the largest likely to be a “425 Project” satellite for South Korea’s military. SpaceX says it continues to see strong interest in its rideshare missions, both for Transporter and Bandwagon. “We heard loud and clear from customers they wanted these services,” Stephanie Bednarek, vice president of commercial sales at SpaceX, said during a panel at the Satellite 2024 conference last month. “It’s going great and we’re really happy.” (submitted by EllPeaTea and Ken the Bin)

Relativity remains "confident" in Terran R in 2026. That's according to Josh Brost, chief revenue officer at Relativity Space, which is developing the medium-lift Terran R rocket. He spoke to Space News at the Space Symposium, noting that construction of the vehicle's launch pad at Cape Canaveral Space Launch Complex-16 is underway.

Some help from the military ... Relativity is benefiting from close collaboration with the Space Force, Brost said, which is providing valuable input to ensure the reusable Terran-R can meet stringent requirements. “We are highly motivated by the feedback we continue to get from the Space Force and from customers,” said Brost. “There’s a strong feeling that there just aren’t enough choices or enough competition, particularly in the medium and heavy launch market.” (submitted by Ken the Bin)

Delta IV Heavy bows out in style. In a pair of long stories, Ars marked the final launch of the Delta IV Heavy rocket, built by United Launch Alliance. The first of these recounts the history of the Delta line of rockets and the origins of the Delta IV Heavy more than two decades ago. All but two of the Delta IV Heavy flights launched payloads for the Air Force or the National Reconnaissance Observatory. NASA used the Delta IV Heavy twice for important missions. In 2014, NASA's Orion crew spacecraft launched on a Delta IV Heavy for an unpiloted orbital test flight, and in 2018, NASA's Parker Solar Probe did so.

A fireball lighting the future ... A second article describes the spectacle of watching the massive rocket liftoff, as it always looked like it was about to blow up due to a fireball engulfing the vehicle. This was due to the deliberate ignition of excess hydrogen. Additionally, although it was tremendously expensive, the Delta IV Heavy offered a preview of what the world might look like with the advent of commercial heavy-lift rockets. There was a time, now about 20 years ago, when the Delta IV Heavy was considered the primary launch vehicle for the Orion spacecraft NASA was developing. (submitted by Ken the Bin)

SpaceX planning upgrades to Starship. As part of a 45-minute speech last weekend at the Starbase facility in South Texas, SpaceX founder Elon Musk spoke about the booster for Starship, the upper stage, and the company's plans to ultimately deliver millions of tons of cargo to Mars for a self-sustaining civilization. To meet the company's needs for the Moon and Mars, Ars reports, Starship will get bigger. It will do so primarily by expanding its length. Musk outlined the company's plans for a "Starship 2," capable of launching 100 tons to low-Earth orbit in fully reusable mode, and "Starship 3," with a capacity of 200 or more tons.

A bit bigger than the Falcon 1 ... If this seems unrealistic, consider that SpaceX performed four major block upgrades to the Falcon 9 rocket from 2010 to 2018, more than doubling its performance. The final Starship 3 vehicle will be about 500 feet (150 meters) tall, about 20 percent larger than the current vehicle. This will allow for additional propellant to increase lift capacity. Musk said the company should be able to launch Starships for less than the original price of the Falcon 1 rocket, which was $6 million. Starship would carry 400 times the payload, however.

Angara rocket launches from Vostochny. Russia successfully launched the Angara A5 rocket on a test flight Thursday from the Vostochny Cosmodrome in the Far East, Reuters reports. This was the third attempt after two last-second launch aborts. Russia began the Angara project shortly after the 1991 break-up of the Soviet Union as a Russian-made launch vehicle that would ensure access to space even without the Baikonur Cosmodrome, which Russia rents from Kazakhstan.

Waiting for a long time ... However, progress has been slow. It seems like the vehicle has been in test mode forever. It has been nearly 10 years since Russia launched the first Angara test flights, and this was the fourth test flight of the heaviest version of Angara, A5. Presumably this is the last test flight of the vehicle, which is capable of lifting up to 24.5 metric tons to low-Earth orbit. (submitted by EllPeaTea and Jay50001)

Next three launches

April 13: Falcon 9 | Starlink 6-49 | Cape Canaveral Space Force Station, Florida | 01:22 UTC

April 15: Long March 2D | Unknown payload | Jiuquan Satellite Launch Center, China | 04:10 UTC

April 17: Falcon 9 | Starlink 6-51 | Kennedy Space Center, Florida | 21:24  UTC

The complex cells that underlie animals and plants have a large collection of what are called organelles—compartments surrounded by membranes that perform specialized functions. Two of these were formed through a process called endosymbiosis, in which a once free-living organism is incorporated into a cell. These are the mitochondrion, where a former bacteria now handles the task of converting chemical energy into useful forms, and the chloroplast, where photosynthesis happens.

The fact that there are only a few cases of organelles that evolved through endosymbiosis suggests that it's an extremely rare event. Yet researchers may have found a new case, in which an organelle devoted to fixing nitrogen from the atmosphere is in the process of evolving. The resulting organelle, termed a nitroplast, is still in the process of specialization.

Getting nitrogen

Nitrogen is one of the elements central to life. Every DNA base, every amino acid in a protein contains at least one, and often several, nitrogen atoms. But nitrogen is remarkably difficult for life to get ahold of. N₂ molecules might be extremely abundant in our atmosphere, but they're extremely difficult to break apart. The enzymes that can, called nitrogenases, are only found in bacteria, and they don't work in the presence of oxygen. Other organisms have to get nitrogen from their environment, which is one of the reasons we use so much energy to supply nitrogen fertilizers to many crops.

Some plants (notably legumes), however, can obtain nitrogen via a symbiotic relationship with bacteria. These plants form specialized nodules that provide a habitat for the nitrogen-producing bacteria. This relationship is a form of endosymbiosis, where microbes take up residence inside an organism's body or cells, with each organism typically providing chemicals that the other needs.

In more extreme cases, endosymbiosis can become obligatory. with neither organism able to survive without the other. In many insects, endosymbionts are passed on to offspring during the production of eggs, and the microbes themselves often lack key genes that would allow them to live independently.

But even states like this fall short of the situation found in mitochondria and chloroplasts. These organelles are thoroughly integrated into the cell, being duplicated and distributed when cells divide. They also have minimal genomes, with most of their proteins made by the cell and imported into the organelles. This level of integration is the product of over a billion years of evolution since the endosymbiotic relationship first started.

It's also apparently a difficult process, based on its apparent rarity. Beyond mitochondria and chloroplasts, there's only one confirmed example of a more recent endosymbiosis between eukaryotes and a bacterial species. (There are a number of cases where eukaryotic algae have been incorporated by other eukaryotes. Because these cells have compatible genetics, this occurs with a higher frequency.)

That's why finding another example is such an exciting prospect.

That’s no endosymbiont

The algae Braarudosphaera bigelowii seemed like it might be an interesting case. It clearly has an endosymbiotic cyanobacteria living in its cells, and there were indications that the bacteria had a compact genome, suggesting it had lost some genes. But, since we couldn't culture B. bigelowii, it was tough to assess the degree to which the bacteria had integrated with its host. But a large international team has now managed to get it to grow in the lab, allowing a more detailed characterization.

They found that a single internalized bacteria occupies a specific area within the cell's structure, near its posterior. Using isotopes as tracers, they found that carbon dioxide taken up by B. bigelowii was transferred to the bacteria. Meanwhile, the cell could also fix nitrogen. Since some cyanobacteria species are able to fix nitrogen, this was almost certainly due to the bacterial symbiote. Nitrogen-fixing only occurred during the day, suggesting the activity was integrated into the cell's metabolism.

A further sign of the bacteria's integration came when the researchers examined cell division. The bacteria is duplicated at the same time as the cell's mitochondria, and one copy is deposited in each of the two daughter cells.

The researchers separated out the two cells and purified proteins from each. They found that hundreds of proteins made by the algal cells ended up inside the bacteria, with their levels varying over the day/night cycle (more were present during daylight hours). Checking the genes that encode these proteins, the researchers found that they all shared a common sequence that directs them to the bacteria and then is clipped off when the protein is transported inside. Similar systems are used by mitochondria and chloroplasts.

The list of proteins found inside the bacteria showed that it contains everything necessary to fix nitrogen. At the same time, it doesn't have what's needed to use CO₂ from the atmosphere as a carbon source, which is why it has to obtain its carbon from the surrounding cell.

An organelle, not a symbiote

All of these properties—the coordinated replication, the biochemical specialization, the existence of a system for importing proteins—are features of organelles, not endosymbiosis. So, the researchers conclude that what was once an endosymbiont has evolved into an organelle specialized in fixing nitrogen, and term it a nitroplast. This is only the fourth example of the evolution of an organelle, making it an impressive discovery.

Unlike things like mitochondria and chloroplasts, however, the nitroplast is limited to a single lineage of algae. That's likely because of its relatively recent origin; it's estimated that the relationship between the nitroplast and its host cell only dates aback about 100 million years, versus the billions of years for the other organelles. Still, its evolution would be extremely valuable for something like algae, which may live in environments where nitrogen sources are rare.

Might that change over time? The evolution of multicellularity is also fairly rare, and B. bigelowii would find itself competing with a huge range of existing multicellular species, so that seems unlikely. But a number of predatory cells have become photosynthetic by ingesting former free-living algae, and there's a chance that the nitroplast could spread this way, eventually enabling a range of single-celled algae to fix nitrogen.

So, this is unlikely to have a major impact on life on Earth anytime soon, barring a science-fiction future in which we understand the system well enough to engineer plant cells to host nitroplasts.

Science, 2024. DOI: 10.1126/science.adk1075  (About DOIs).

Sometime around 660 CE, silver coinage replaced gold as the dominant form of currency in northwest Europe. But what was the source of all that silver? According to a recent paper published in the journal Antiquity, silver for the earlier post-Roman coins during this period came from Byzantine silver plate, while silver for the later coins most likely came from mines located in Melle, Aquitaine.

“This was such an exciting discovery," said co-author Rory Naismith, a medieval historian at the University of Cambridge. "I proposed Byzantine origins a decade ago but couldn’t prove it. Now we have the first archaeometric confirmation that Byzantine silver was the dominant source behind the great seventh-century surge in minting and trade around the North Sea.”

There are a number of high-tech tools that can be used to learn more about historic currencies. For instance, Michael Wiescher, a nuclear physicist at the University of Notre Dame, has combined XRF scaling with PIXE mapping of Roman denarii to test the currency's quality and learn more about the production techniques. Working with his undergraduate students, he has also used electron spectroscopy to measure the silver content of each coin and learn about how the impurities were distributed.

The Roman silver denarius was the backbone currency of the Roman Empire between 200 BCE and 300 CE. During Nero's reign, the coins were required to be 92.5 percent silver to protect the currency against inflation and devaluation. But the analysis of coins from 250 to 350 CE showed declining percentages of silver because the Roman mints gradually debased the denarius to increase their profits. By 295 CE, the silver content was just about 5 percent. Wiescher's analysis revealed that most of the coins are composed of silver and copper and that sulfur and iron impurities led to corrosion in some of them.

The same trick of replacing some of the silver in coins with copper showed up again thousands of years later in Spain's Latin American colonies. Wiescher analyzed 91 silver rials dated between the 16th and 18th centuries, from Mexico and Potosi, Bolivia.

Between 1645 and 1648, the silver content dropped from 92.5 percent sterling to just 70–80 percent; the rest was a copper admixture. When this was discovered in the 17th century, the silver market in Spain crashed and the coins were devalued, with devastating effects on the colonial Spanish economy. Some of that silver from Spain and Mexico eventually made its way to the early American colonies. The Boston Mint used Spanish silver between 1653 and 1686 for minting coins, once again adding a little copper or iron to increase their profits.

In 2022, scientists used a variety of physics-based methods—classic light microscopy, ultraviolet imaging, scanning electron microscopy, and reflection mode Fourier-transform infrared spectroscopy—to analyze a cache of Roman coins that was discovered in Transylvania in 1713. Several bore the portrait of a Roman emperor named Sponsian and hence were thought to be forgeries, since there are no historical records of a Roman emperor with that name.

The 2022 analysis suggested the coins were probably genuine, speculating that Sponsian may have been an obscure Roman military commander in the Roman province of Dacia, an isolated gold mining outpost that overlaps with modern-day Romania. Given their mining resources, Dacia could have minted their own coins with Sponsian's image, which would have helped cement his authority and maintain economic stability and social order until the area was finally evacuated between 271 and 275 CE.

For this latest study, the coinage in question is the silver currency that came on the scene around 660 CE, which marked "a major transformation in the early medieval economy," according to the authors. Historians have long debated where the silver for that coinage came from. Did people melt down Roman plate and/or recycle Roman scrap metal? Was it imported from the Byzantine, as Naismith argued in 2012? Or was there a revival in silver mining around this time in medieval Europe, particularly in Melle in western France?

“There has been speculation that the silver came from Melle in France, or from an unknown mine, or that it could have been melted down church silver," said Naismith. "But there wasn't any hard evidence to tell us one way or the other, so we set out to find it.”

Prior work had tested coins and artifacts from Melle silver mines, but less attention had been paid to coins minted in England, the Netherlands, Belgium, and northern France. Naismith et al. used a combination of lead isotope and trace element analysis to study 49 medieval silver pennies and denarii from the Fitzwilliam Museum in Cambridge. For the lead isotope analysis, they relied on a new technique called "portable laser ablation" to collect microscopic samples onto Teflon filters—a less invasive approach than traditional methods while maintaining high precision.

As one might expect, most of the coins contained silver. It was the respective amounts of gold, bismuth, and other elements that provided clues to the origin of the silver used in the coins. Per Naismith et al., 29 of the earlier coins (dated between 660 and 750 CE) showed chemical and isotopic signatures consistent with Byzantine silver from the third and early seventh centuries, including between 0.6 and 2 percent gold. There is no known European ore source matching those signatures, which are also not consistent with late Western Roman silver coins. This provides evidence of international trade relations between modern-day France, the Netherlands, and England.

Naismith points out that high-ranking people in England and Francia at this time possessed a great deal of silver artifacts, as evidenced by the significant cache of Byzantine discovered at Sutton Hoo. He estimates that this cache alone, had it been melted down, would have produced some 10,000 early pennies.

“These beautiful prestige objects would only have been melted down when a king or lord urgently needed lots of cash," said co-author Jane Kershaw of the University of Oxford. "Something big would have been happening, a big social change. This was quantitative easing, elites were liquidating resources and pouring more and more money into circulation. It would have had a big impact on people’s lives. There would have been more thinking about money and more activity with money involving a far larger portion of society than before.”

The remaining 20 coins analyzed for the study dated to a later period between 750 and 820 CE. This silver had substantially lower amounts of gold (in some cases, less than 0.01 percent), consistent with silver mined at Melle. The older, now debased silver was likely captured and refined for re-minting, combined with newer silver from Melle.

Naismith et al. suggest that Charlemagne was behind the shift to silver from Melle, citing records from the 860s in which King Charles the Bald (grandson of Charlemagne) decided to reform his kingdom's coinage and provided the mints with some silver to get the process going. Charlemagne may have done something similar, providing silver sourced from Melle to his mints. "It was only following the major reform of coinage by Charlemagne in 792–793 that coins from all surveyed mints showed a strong shift toward Melle-like silver," the authors concluded.

Antiquity, 2024. DOI: 10.15184/aqy.2024.33  (About DOIs).

Modern life can be fraught with confusion. Should I answer my cellphone in a crowded place? (No.) Where do I stand on an escalator? (On the right—let people walk on the left.) And what are the social rules when it comes to recharging my electric vehicle? Thankfully, that last question has now been addressed by Debrett's, a British publisher with a name now synonymous with etiquette, in the recently published 2024 edition of "A-Z of Modern Manners."

Debrett's has been publishing guides on manners and etiquette since the last time electric vehicles were a thing, but it first put together a list of dos and do-nots for EV drivers last year as a standalone guide with British car brand Vauxhall. Now, it has added the advice to this year's edition of the general etiquette guide.

Although Debrett's is writing for a UK audience, with its ingrained ideas about class structure, the advice also applies to this side of the Atlantic, and it's probably timely now that Tesla is opening up its Supercharger network to non-Tesla EVs. Here is some of the advice.

Don’t cut in line

As EV adoption grows, particularly in places like California, some charging locations can generate demand that outstrips the number of charging plugs available. If every charger at a station is occupied, see if there's a queue you're supposed to join—being unaware and jumping in front of other drivers who have been waiting longer than you won't make a good impression.

If you find yourself waiting with other EV drivers, make small talk to pass the time. "If you establish a relationship with fellow motorists, they’re much more likely to be accommodating when it comes to negotiating charging time," the guide notes.

Debrett's also suggests you park neatly within the lines and don't straddle spaces. This may be less of a problem in the US, where we make our bays big, but remember that "no electric vehicle has special priority, whether that be a full EV or Plug-in Hybrid (PHEV)."

Know something about your EV

Being aware of your car's charging needs is important. For example, PHEV drivers have no need for DC fast chargers unless they are in a CHAdeMO-equipped Mitsubishi Outlander, so don't take your AC-only vehicle to a DC-only location.

And for EV drivers at DC fast chargers, you should know how long it takes your car to reach an 80 percent state of charge. After this point, an EV battery significantly restricts the amount of charge it draws, throttling back the charger in the process. Charging from 80 to 100 percent can take as long as 10 to 80 percent takes, so plan on leaving the public charger at that point unless absolutely necessary.

Be polite

While you shouldn't jump the queue, Debrett's says it's OK to discreetly check how long another car has left in its session. If you see it's almost done and that a driver is with that car, you can politely ask how much longer they're going to take. For example: "I hope you don’t mind me asking, but I notice you’re nearly fully charged. Would it be okay if I started to plug in soon?" And remember to be thankful if they say yes.

Don’t be bullied

Depending on where you are, there may be certain protections for EV charging spots that prohibit internal combustion engine-powered vehicles from "ICEing out" charging bays. Debrett's suggests checking street signs to familiarize yourself with any local peculiarities.

While there may be rules or regulations about only leaving your EV in a spot while it's charging or not ICEing out an EV charger, if the car in question is unattended, "in practice there is very little you can do when confronted by a selfish motorist, unless you catch them in the act of parking, when you can politely point out the sign."

You could leave a note

If you plan on leaving your car while it charges, you might want to leave a note in the window telling other drivers how long you'll be.

Should you find a charging spot occupied by a fully charged car, try to stay calm and don't unplug the other person's car in a fit of rage. "A careless move could harm the car or the charger, and you don’t want your understandable irritation to lead to you inflicting criminal damage," Debrett's points out.

Plan ahead

Most EV drivers will already know this one, especially if they have tried to road-trip. If you plan on charging while you're out and about, you can prepare yourself by looking up charging facilities in an app like PlugShare or A Better Route Planner.

These usually have some degree of crowdsourced ratings for charger reliability and allow you to enter the details of your EV and how much charge you want to have when you arrive in order to calculate which chargers to visit along the way.

Don’t be careless with cables

This advice is probably more germane to the UK and Europe, where street-side charging is much more common, although a number of US cities (like Los Angeles and Kansas City) have also deployed streetlamp AC chargers in recent years.

If you're charging on-street, be considerate and make sure you aren't breaking any local laws or regulations. And beware of creating a trip hazard—be like my Chevy Volt-owning neighbor and use a pedestrian cable protector so people on foot or bike aren't inconvenienced by your charging car.

Charging at a friend’s

If you're planning on plugging in at a friend's place, be polite about it. Don't assume you can just plug in when you arrive; instead, ask politely if it's OK to use their electricity and, if so, if they can direct you to the nearest suitable outlet.

Here in the US, that will almost certainly mean a 120 V outlet, so don't expect to charge quickly, or ask whether it's OK to disconnect their dryer so you can access the more powerful 240 V outlet. And if you think you've used a lot of their electricity, "it is a gracious gesture to leave a parting gift."

Be tidy

Finally, leave things as you wish to find them. That means reseating the charging cable back in its holder, not just leaving it on the ground as you drive off. And if you've encountered a problem, don't keep it to yourself. Report broken chargers to their operators so they know they have to come to fix them and share that information on PlugShare so other EV drivers have advanced warning. You could even leave a note on a broken charger to save other drivers the hassle of parking in that spot and then having to move.

Peter Higgs, the shy, somewhat reclusive physicist who won a Nobel Prize for his theoretical work on how the Higgs boson gives elementary particles their mass, has died at the age of 94. According to a statement from the University of Edinburgh, the physicist passed "peacefully at home on Monday 8 April following a short illness."

“Besides his outstanding contributions to particle physics, Peter was a very special person, a man of rare modesty, a great teacher and someone who explained physics in a very simple and profound way," Fabiola Gianotti, director general at CERN and former leader of one of the experiments that helped discover the Higgs particle in 2012, told The Guardian. "An important piece of CERN’s history and accomplishments is linked to him. I am very saddened, and I will miss him sorely.”

The Higgs boson is a manifestation of the Higgs field, an invisible entity that pervades the Universe. Interactions between the Higgs field and particles help provide particles with mass, with particles that interact more strongly having larger masses. The Standard Model of Particle Physics describes the fundamental particles that make up all matter, like quarks and electrons, as well as the particles that mediate their interactions through forces like electromagnetism and the weak force. Back in the 1960s, theorists extended the model to incorporate what has become known as the Higgs mechanism, which provides many of the particles with mass. One consequence of the Standard Model's version of the Higgs boson is that there should be a force-carrying particle, called a boson, associated with the Higgs field.

Despite its central role in the function of the Universe, the road to predicting the existence of the Higgs boson was bumpy, as was the process of discovering it. As previously reported, the idea of the Higgs boson was a consequence of studies on the weak force, which controls the decay of radioactive elements. The weak force only operates at very short distances, which suggests that the particles that mediate it (the W and Z bosons) are likely to be massive. While it was possible to use existing models of physics to explain some of their properties, these predictions had an awkward feature: just like another force-carrying particle, the photon, the resulting W and Z bosons were massless.

Over time, theoreticians managed to craft models that included massive W and Z bosons, but they invariably came with a hitch: a massless partner, which would imply a longer-range force. In 1964, however, a series of papers was published in rapid succession that described a way to get rid of this problematic particle. If a certain symmetry in the models was broken, the massless partner would go away, leaving only a massive one.

The first of these papers, by François Englert and Robert Brout, proposed the new model in terms of quantum field theory; the second, by Higgs (then 35), noted that a single quantum of the field would be detectable as a particle. A third paper, by Gerald Guralnik, Carl Richard Hagen, and Tom Kibble, provided an independent validation of the general approach, as did a completely independent derivation by students in the Soviet Union.

At that time, "There seemed to be excitement and concern about quantum field theory (the underlying structure of particle physics) back then, with some people beginning to abandon it," David Kaplan, a physicist at Johns Hopkins University, told Ars. "There were new particles being regularly produced at accelerator experiments without any real theoretical structure to explain them. Spin-1 particles could be written down comfortably (the photon is spin-1) as long as they didn’t have a mass, but the massive versions were confusing to people at the time. A bunch of people, including Higgs, found this quantum field theory trick to give spin-1 particles a mass in a consistent way. These little tricks can turn out to be very useful, but also give the landscape of what is possible."

Ironically, Higgs' seminal paper was rejected by the European journal Physics Letters. He then added a crucial couple of paragraphs noting that his model also predicted the existence of what we now know as the Higgs boson. He submitted the revised paper to Physical Review Letters in the US, where it was accepted. He examined the properties of the boson in more detail in a 1966 follow-up paper.

Higgs later admitted that he did not initially realize how significant his theory would turn out to be. "It wasn't clear at the time how it would be applied in particle physics, and those of us who did the work in '64 were looking in the wrong place for the application," he said. And he wasn't the only one. "Nobody else took what I was doing seriously, so nobody would want to work with me," he said. "I was thought to be a bit eccentric and maybe cranky." Higgs only published a handful of papers after those early contributions and told The Guardian in 2013 that these days, he would probably not be considered productive enough to warrant a university professorship.

Fortunately, other physicists were able to build on Higgs' early work. By 1967, Steve Weinberg had extended the Higgs mechanism to account for the mass of electrons and heavier leptons, and in 1971, Gerard ‘t Hooft and Martinus Veltman figured out how to get rid of a few annoying infinities in some of the equations. By 1983, the W and Z bosons had had their masses determined, providing an experimental validation of some of the predictions made by the theoreticians.

It took the construction of the Large Hadron Collider at CERN to experimentally detect the elusive signature of the Higgs boson. On July 4, 2012, CERN hosted two seminars, streamed live around the world, announcing the long-awaited discovery of the Higgs boson based on data from two different yet complementary experiments (ATLAS and CMS) —the last piece of the Standard Model puzzle. Higgs, then 83 and retired, was at CERN when the discovery was announced, largely thanks to CERN physicist John Ellis, who left Higgs a phone message: "Tell Peter that if he doesn't come to CERN on Wednesday, he will very probably regret it."

The assembled scientists gave a standing ovation when the talks were over, and a visibly emotional Higgs pulled out a handkerchief and wiped away a tear. "During the talks, I was still distancing myself from it all, but when the seminar ended, it was like being at a football match when the home team had won," Higgs later recalled. "It was like being knocked over by a wave." But he didn't stick around for the afterparty, preferring to celebrate on the flight home with a can of London Pride beer.

Higgs received his first nomination for the Nobel Prize in Physics back in 1980; the possibility that he might win one day was the main reason, he claimed, that he didn't get the sack from the University of Edinburgh. That day arrived in 2013 when Higgs shared the Nobel Prize with Englert "for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles...."

Not liking fuss, he planned to leave town for the West Highlands, but his car battery was dead. He went for lunch in Leith instead, and when a neighbor saw him and broke the news of his award, he jokingly feigned ignorance and said, "What award?" Higgs turned down a knighthood in 1999, but Queen Elizabeth II appointed him to the Order of the Companion of Honor in 2013.

“Even though he didn’t much enjoy it, he felt a responsibility to use the public profile his achievements brought him for the good of science, and he did so many times," University College London physicist Jon Butterworth, a member of the ATLAS experiment, told The Guardian, calling Peter Higgs. "a hero to the particle physics community. The particle that carries his name is perhaps the single most stunning example of how seemingly abstract mathematical ideas can make predictions which turn out to have huge physical consequences.”

Higgs is survived by two sons, Chris and Jonny, daughter-in-law Suzanne, and two grandchildren. His wife, Jody, from whom he was separated, died in 2008.

The final flight of United Launch Alliance's Delta IV Heavy rocket took off Tuesday from Cape Canaveral, Florida, with a classified spy satellite for the National Reconnaissance Office.

The Delta IV Heavy, one of the world's most powerful rockets, launched for the 16th and final time Tuesday. It was the 45th and last flight of a Delta IV launcher and the final rocket named Delta to ever launch, ending a string of 389 missions dating back to 1960.

United Launch Alliance (ULA) tried to launch this rocket on March 28 but aborted the countdown about four minutes prior to liftoff due to trouble with nitrogen pumps at an off-site facility at Cape Canaveral. The nitrogen is necessary for purging parts inside the Delta IV rocket before launch, reducing the risk of a fire or explosion during the countdown.

The pumps, operated by Air Liquide, are part of a network that distributes nitrogen to different launch pads at the Florida spaceport. The nitrogen network has caused problems before, most notably during the first launch campaign for NASA's Space Launch System rocket in 2022. Air Liquide did not respond to questions from Ars.

A flawless liftoff

With a solution in place, ULA gave the go-ahead for another launch attempt Tuesday. After a smooth countdown, the final Delta IV Heavy lifted off from Cape Canaveral Space Force Station at 12:53 pm EDT (16:53 UTC).

Three hydrogen-fueled RS-68A engines made by Aerojet Rocketdyne flashed to life in the final seconds before launch and throttled up to produce more than 2 million pounds of thrust. The ignition sequence was accompanied by a dramatic hydrogen fireball, a hallmark of Delta IV Heavy launches, that singed the bottom of the 235-foot-tall (71.6-meter) rocket, turning a patch of its orange insulation black. Then, 12 hold-down bolts fired and freed the Delta IV Heavy for its climb into space with a top-secret payload for the US government's spy satellite agency.

Heading east from Florida's Space Coast, the Delta IV Heavy appeared to perform well in the early phases of its mission. After fading from view from ground-based cameras, the rocket's two liquid-fueled side boosters jettisoned around four minutes into the flight, a moment captured by onboard video cameras. The core stage engine increased power to fire for a couple more minutes. Nearly six minutes after liftoff, the core stage was released, and the Delta IV upper stage took over for a series of burns with its RL10 engine.

At that point, ULA cut the public video and audio feeds from the launch control center, and the mission flew into a news blackout. The final portions of rocket launches carrying National Reconnaissance Office (NRO) satellites are usually performed in secret.

In all likelihood, the Delta IV Heavy's upper stage was expected to fire its engine at least three times to place the classified NRO satellite into a circular geostationary orbit more than 22,000 miles (nearly 36,000 kilometers) over the equator. In this orbit, the spacecraft will move in lock-step with the planet's rotation, giving the NRO's newest spy satellite constant coverage over a portion of the Earth.

It will take about six hours for the rocket's upper stage to deploy its payload into this high-altitude orbit and only then will ULA and the NRO declare the launch a success.

Eavesdropping from space

While the payload is classified, experts can glean a few insights from the circumstances of its launch. Only the largest NRO spy satellites require a launch on a Delta IV Heavy, and the payload on this mission is "almost certainly" a type of satellite known publicly as an "Advanced Orion" or "Mentor" spacecraft, according to Marco Langbroek, an expert Dutch satellite tracker.

The Advanced Orion satellites require the combination of the Delta IV Heavy rocket’s lift capability, long-duration upper stage, and huge, 65-foot-long (19.8-meter) trisector payload fairing, the largest payload enclosure of any operational rocket. In 2010, Bruce Carlson, then-director of the NRO, referred to the Advanced Orion platform as the "largest satellite in the world."

When viewed from Earth, these satellites shine with the brightness of an eighth-magnitude star, making them easily visible with small binoculars despite their distant orbits, according to Ted Molczan, a skywatcher who tracks satellite activity.

"The satellites feature a very large parabolic unfoldable mesh antenna, with estimates of the size of this antenna ranging from 20 to 100 (!) meters," Langbroek writes on his website, citing information leaked by Edward Snowden.

The purpose of these Advanced Orion satellites, each with mesh antennas that unfurl to a diameter of up to 330 feet (100 meters), is to listen in on communications and radio transmissions from US adversaries, and perhaps allies. Six previous Delta IV Heavy missions also likely launched Advanced Orion or Mentor satellites, giving the NRO a global web of listening posts parked high above the planet.

With the last Delta IV Heavy off the launch pad, ULA has achieved a goal of its corporate strategy sent into motion a decade ago, when the company decided to retire the Delta IV and Atlas V rockets in favor of a new-generation rocket named Vulcan. The first Vulcan rocket successfully launched in January, so the last few months have been a time of transition for ULA, a 50-50 joint venture owned by Boeing and Lockheed Martin.

"This is such an amazing piece of technology: 23 stories tall, half a million gallons of propellant, two and a quarter million pounds of thrust, and the most metal of all rockets, setting itself on fire before it goes to space," Bruno said of the Delta IV Heavy before its final launch. "Retiring it is (key to) the future, moving to Vulcan, a less expensive, higher-performance rocket. But it’s still sad.”

"Everything that Delta has done ... is being done better on Vulcan, so this is a great evolutionary step," said Bill Cullen, ULA's launch systems director. "It is bittersweet to see the last one, but there are great things ahead."

Goodbye, Delta

The name Delta is familiar to those who know their space history. Alongside rocket families like the Atlas, Saturn, Titan, and more recently, Falcon, Delta was an icon of spaceflight for more than a half-century. The first Delta rocket launched on May 13, 1960, but it fell into the Atlantic Ocean after experiencing an upper-stage failure. Three months later, the Delta rocket had its first success and placed an early rudimentary communications satellite into orbit.

Delta rockets launched many of the first communications satellites, deployed the first generation of GPS navigation satellites, and dispatched NASA's first rovers to Mars.

Ending at 389 launches, Delta rockets rank second in number of flights for a US orbital-class rocket, trailing only the Atlas family. SpaceX's Falcon rocket family is close on Delta's heels and could surpass the 389-flight milestone later this year.

However, there's an important distinction to make with the Delta IV rocket, which debuted in 2002. The Delta IV shares little in common with the older Delta rockets, which could trace at least some of their design lineage to the Thor program, a Cold War-era ballistic missile later converted into a satellite launcher.

The last of that older family of Delta rockets, the Delta II, launched for the final time in 2018. The Delta II was a workhorse for the Air Force, NASA, and the commercial satellite market through the 1990s and into the 2000s. It was also the first rocket to fly with fuel tanks manufactured using friction stir welding, a process improvement that produces structures with fewer detects and higher-strength bonds. This technology was later applied to the Delta IV, an upgraded version of the space shuttle's external fuel tank, SpaceX's Falcon 9 and Falcon Heavy rockets, and NASA's Space Launch System.

The Delta IV was a clean-sheet design, initially conceived by McDonnell Douglas, that won a contract from the Air Force in 1998, alongside Lockheed Martin's Atlas V rocket, to become the primary new expendable launch vehicle for the military's fleet of satellites.

The Delta IV program became part of Boeing when that company merged with McDonnell Douglas in 1997.

A rocket of its time

Boeing developed the Delta IV Heavy variant, which debuted in 2004, to launch the heaviest satellites owned by the military and the NRO. It was primarily designed as a replacement for the Titan IV rocket, which retired in 2005, to loft NRO eavesdropping satellites and the NRO's massive bus-size Keyhole imaging platforms, essentially Hubble-class telescopes pointed at Earth.

Boeing later merged its Delta rocket program with the rival Atlas from Lockheed Martin, forming ULA in 2006.

All but two of the Delta IV Heavy flights launched payloads for the Air Force or the NRO. NASA used the Delta IV Heavy twice for important missions. In 2014, NASA's Orion crew spacecraft launched on a Delta IV Heavy for an unpiloted orbital test flight, and in 2018, NASA's Parker Solar Probe departed Earth on a Delta IV Heavy rocket on a first-of-its-kind voyage to fly through the atmosphere of the Sun.

At one time, the Delta IV Heavy was the only option for getting the government's largest spy satellites into orbit. Now, SpaceX's Falcon Heavy rocket is available. When flying in expendable mode, the Falcon Heavy has more lift capability than the Delta IV Heavy does to any orbit. SpaceX is developing a larger fairing for the Falcon Heavy to match the Delta IV Heavy's payload volume, giving it the ability to perform all of the Delta IV Heavy's missions at a fraction of the cost.

ULA's Vulcan rocket will also soon be certified for national security launches. The largest version of Vulcan will outlift the Delta IV Heavy using a central core stage and strap-on solid rocket boosters without needing to fly in a triple-core configuration, which drives up complexity and cost.

A single launch on a Delta IV Heavy has cost as much as $400 million, although the government secured a somewhat lower price from ULA for buying in bulk the final three missions on Delta IV Heavy. The medium-lift version of the Delta IV launched a commercial satellite on its first flight in 2002, but no more commercial customers ever bought a Delta IV flight, despite a nearly perfect success record.

The Space Force hasn't decided on the future of the Delta IV launch pad at Cape Canaveral Space Force Station, but SpaceX is interested in converting the pad to a new home for its gigantic Starship rocket. Environmental reviews are underway before SpaceX can take over the site.

Life-forms with no brain are capable of some astounding things. It might sound like sci-fi nightmare fuel, but some bacteria can wage kamikaze chemical warfare.

Pathogenic bacteria make us sick by secreting toxins. While the release of smaller toxin molecules is well understood, methods of releasing larger toxin molecules have mostly eluded us until now. Researcher Stefan Raunser, director of the Max Planck Institute of Molecular Physiology, and his team finally found out how the insect pathogen Yersinia entomophaga (which attacks beetles) releases its large-molecule toxin.

They found that designated “soldier cells” sacrifice themselves and explode to deploy the poison inside their victim. “YenTc appears to be the first example of an anti-eukaryotic toxin using this newly established type of secretion system,” the researchers said in a study recently published in Nature.

Silent and deadly

Y. entomophaga is part of the Yersinia genus, relatives of the plague bacteria, which produce what are known as Tc toxins. Their molecules are huge as far as bacterial toxins go, but, like most smaller toxin molecules, they still need to make it through the bacteria's three cell membranes before they escape to damage the host. Raunser had already found in a previous study that Tc toxin molecules do show up outside the bacteria. What he wanted to see next was how and when they exit the bacteria that makes them.

To find out what kind of environment is ideal for Y. entomophaga to release YenTC, the bacteria were placed in acidic (PH under 7) and alkaline (PH over 7) mediums. While they did not release much in the acidic medium, the bacteria thrived in the high PH of the alkaline medium, and increasing the PH led it to release even more of the toxin. The higher PH environment in a beetle is around the mid-end of its gut, so it is now thought that most of the toxin is liberated when the bacteria reach that area.

How YenTc is released was more difficult to determine. When the research team used mass spectrometry to take a closer look at the toxin, they found that it was missing something: There was no signal sequence that indicated to the bacteria that the protein needed to be transported outside the bacterium. Signal sequences, also known as signal peptides, are kind of like built-in tags for secretion. They are in charge of connecting the proteins (toxins are proteins) to a complex at the innermost cell membrane that pushes them through. But YenTC apparently doesn’t need a signal sequence to export its toxins into the host.

About to explode

So how does this insect killer release YenTc, its most formidable toxin? The first test was a process of elimination. While YenTc has no signal sequence, the bacteria have different secretion systems for other toxins that it releases. Raunser thought that knocking out these secretion systems using gene editing could possibly reveal which one was responsible for secreting YenTc. Every secretion system in Y. entomophaga was knocked out until no more were left, yet the bacteria were still able to secrete YenTc.

The researchers then used fluorescence microscopy to observe the bacteria releasing its toxin. They inserted a gene that encodes a fluorescent protein into the toxin gene so the bacteria would glow when making the toxin. While not all Y. entomophaga cells produced YenTc, those that did (and so glowed) tended to be larger and more sluggish. To induce secretion, PH was raised to alkaline levels. Non-producing cells went about their business, but YenTc-expressing cells only took minutes to collapse and release the toxin.

This is what’s called a lytic secretion system, which involves the rupture of cell walls or membranes to release toxins.

“This prime example of self-destructive cooperation in bacteria demonstrates that YenTc release is the result of a controlled lysis strictly dedicated to toxin release rather than a typical secretion process, explaining our initially perplexing observation of atypical extracellular proteins,” the researchers said in the same study.

Yersinia also includes pathogenic bacteria that cause tuberculosis and bubonic plague, diseases that have devastated humans. Now that the secretion mechanism of one Yersinia species has been found out, Raunser wants to study more of them, along with other types of pathogens, to see if any others have kamikaze soldier cells that use the same lytic mechanism of releasing toxins.

The discovery of Y. entomophaga’s exploding cells could eventually mean human treatments that target kamikaze cells. In the meantime, we can at least be relieved we aren’t beetles.

Nature Microbiology, 2024. DOI: 10.1038/s41564-023-01571-z

What if human blood turned into a sort of rubbery slime that can bounce back into a wound and stop it from bleeding in record time?

Until now, it was a mystery how hemolymph, or insect blood, was able to clot so quickly outside the body. Researchers from Clemson University have finally figured out how this works through observing caterpillars and cockroaches. By changing its physical properties, the blood of these animals can seal wounds in about a minute because the watery hemolymph that initially bleeds out turns into a viscoelastic substance outside of the body and retracts back to the wound.

“In insects vulnerable to dehydration, the mechanistic reaction of blood after wounding is rapid,” the research team said in a study recently published in Frontiers in Soft Matter. “It allows insects to minimize blood loss by sealing the wound and forming primary clots that provide scaffolding for the formation of new tissue.”

Mysterious ooze

Hemolymph has a drastically different composition from vertebrate blood. It is devoid of red blood cells and platelets. The cells that make up hemolymph, known as hemocytes, act like white blood cells in vertebrates, carrying out functions such as eating potentially infectious bacteria and helping form clots over wounds. Some insects have blood richer in hemocytes than others. Even the larval forms of certain species may have more hemocytes in their blood than adults, with many adult butterflies and moths having hemocyte-poor hemolymph compared to the caterpillars.

When experimenting with the sphinx moth caterpillars (Manduca sexta), the researchers placed the caterpillar in a hard plastic sleeve with holes and then made an incision in one of its prolegs. The greenish hemolymph that escaped the wound dripped like water for a few seconds. However, it soon thickened into a viscoelastic fluid that dripped much more slowly. Its final drop did not detach and fall but instead retracted toward the wound.

This all happened within 60 to 90 seconds. Similar results were seen with cockroaches (Periplaneta americana) when the tip of one antenna was severed.

In both species of insects, after the hemolymph retracted, a clot began to form. The scab from this clot became so tough in cockroaches that even a tungsten needle could not penetrate it.

It’s in the blood

To investigate the structure of hemolymph clots, the scientists gathered some of the viscous (but not completely clotted) material from caterpillar and cockroach wounds and examined it using phase-contrast microscopy. Phase contrast enhances contrast and therefore makes it possible to see details (such as cells) in transparent specimens such as hemolymph. The partially clotted hemolymph was made of what are described in the study as “polymeric filaments with embedded hemocytes,” with clots from older wounds being slimier, or thicker, than those from fresher wounds.

Some specimens included pieces of crust from scabs that started to form over healed wounds. These were freeze-dried to prevent any water left from deforming them, then further observed using X-ray, micro-CT, and SEM imaging, which showed that the outer part of the crust, which was most exposed to the air, was more dense. The scab material also contained large aggregates of hemocytes that had assembled themselves into chain structures to form a clot.

How fast can hemocytes start assembling? The team went back and observed viscous but not hardened hemolymph oozing from wounds.

While bleeding stopped after about a minute, hemocytes started to form a scab around three minutes after the formation of the last drop, which retracted after turning into a viscoelastic fluid with polymers strong enough to thicken it and hold it back. Some hemocytes would form pseudopodia (much like amoebas do), which then attached to other hemocytes. The aggregates that resulted made the fluid more and more viscous and eventually formed a scab.

Insect hemolymph is not the only type of bodily fluid that demonstrates viscoelastic properties. Even saliva is more watery when it first leaves the mouth but becomes more viscous with time outside of the body, such as when it stretches down from the end of a dog’s tongue. Human blood is not viscoelastic. However, this study could have implications for human medicine in the future. The Clemson researchers think it is possible that future advances could give us some of the advantages of bugs when it comes to healing wounds.

“We hope that our findings will trigger the interest of biochemists and molecular biologists,” they said, “to design fast-working thickeners for vertebrate blood, including human blood.”

Frontiers in Soft Matter, 2024. DOI: 10.3389/frsfm.2024.1341129