Multiple lines of evidence indicate that modern humans evolved within the last 200,000 years and spread out of Africa starting about 60,000 years ago. Before that, however, the details get a bit complicated. We're still arguing about which ancestral population might have given rise to our lineage. Somewhere about 600,000 years ago, that lineage split off Neanderthals and Denisovans, and both of those lineages later interbred with modern humans after some of them left Africa.

 

Figuring out as much as we currently know has required a mix of fossils, ancient DNA, and modern genomes. A new study argues there is another complicating event in humanity's past: a near-extinction period where almost 99 percent of our ancestral lineage died. However, the finding is based on a completely new approach to analyzing modern genomes, and so it may be difficult to validate.

Tracing diversity

Unless a population is small and inbred, they will have genetic diversity: a collection of differences in their DNA ranging from individual bases up to large rearrangements of chromosomes. These differences are tracked when testing services estimate where your ancestors were likely to originate. Some genetic differences arose recently, while others have been floating around our lineage since before modern humans existed.

 

These differences form the foundation of the new work, which analyzed multiple human genomes based on several well-established principles.

 

The first of these is that, given enough genomes, it's possible to work out what the ancestral states of different areas of the chromosomes were. For example, a variation that's present only in a set of closely related individuals and not anyone else probably arose in their common ancestor. That means the ancestral state of the chromosome lacked that variation.

 

Since we know the rate at which new mutations arise in modern humans, we can use these differences to create a molecular clock. In other words, we can take the number of mutations between the present and an ancestral state, compare that with the rate at which mutations occur, and estimate when that ancestral state was last present in the population.

 

Finally, the number of variations present in a population is related to the population's size. Smaller populations tend to become inbred because it becomes difficult to avoid mating with relatives, leading to the loss of genetic diversity. In addition, there are simply fewer chromosomes around in total in small populations, which limits the potential for diversity. The converse is also true, in that large populations can support more diversity.

 

Put these together, and you have the outlines of what the researchers behind the new work have done. They took the variations present in today's genomes and used them to determine the existence of various ancestral states and when they were likely to have existed. By figuring out how many different ancestral states were present at a given time, they could also estimate the population's size.

Does this actually work?

All of this work is based on probabilities, so the results for any individual bit of chromosome have a fairly high chance of being wrong. But all those individual errors should be wrong in different ways. Given the entire genomes of enough individuals, however, a real signal should emerge from the noise of the individual errors. The big questions are whether the algorithm devised by the authors can recognize a signal and whether we have enough data to allow it to do so.

 

The researchers make their case by creating several model populations that undergo different forms of change. (Examples include a constant population size, constant growth, stasis followed by growth, and so on.) Various algorithms were set loose on this data, including the researchers' software, FitCoal. Most of them had some significant errors, though some did better than others. And FitCoal consistently outperformed everything, producing population size estimates that were, in most cases, difficult to distinguish from the model population.

 

Reassuringly, most of the other algorithms produced results that were similar to those of FitCoal, though their error ranges were significantly larger.

 

The algorithm's accuracy is likely to be the most controversial aspect of this work going forward, though. Unless someone spots an error in the code, then we're likely to have to rely on comparisons with other software. Unfortunately, this sort of software is very computationally expensive. Adding more genomes to the analysis could also provide some clarity, as results could get more accurate with more data to work with. But additional genomes would make the computational challenge even worse.

A long near-extinction

So, what does the new software produce when set loose on human populations? The answer depends on the population. The non-African populations show a relatively constant population size followed by strong growth as their ancestors migrated out of Africa. But the African populations all showed a huge drop in the population size that started around 930,000 years ago and persisted for over 100,000 years.

 

During this time, the effective population size—a measure of the individuals who contributed to maintaining the population—was only about 1,300 individuals. That doesn't mean there were that few members of our ancestral lineage. Other individuals may not have mated, or went off and mated in populations that didn't contribute to our ancestry. But even so, it's a very small population, and would have left our ancestors at risk of extinction. We'd certainly put an equivalent-sized population on the endangered species list today.

 

This isn't a matter of a population that just started out small, either. Tracing diversity back further leads the authors to estimate that 98.7 percent of the ancestral population was lost in a sudden collapse. The event was what's termed a bottleneck, as the entire population went through a sudden and narrow constriction.

 

What about the non-African populations? The researchers show that the out-of-Africa expansion, which created its own bottleneck, interferes with our ability to detect earlier events.

 

Other algorithms, when given the genomes from Africans, show only a minor dip in population size around this time. But, because of how they're structured, they don't have the same temporal resolution as FitCoal, so it's not clear whether we should even expect them to be able to resolve this.

In context

The researchers note that the potential bottleneck took place around the same time as our climate system switched from relatively short, moderate glacial periods to longer and colder ones. They also note that fossils of our ancestors were rare in Africa during this period. So, they think all three are related.

 

The big problem with this idea is that there are many fossils of human relatives from this period outside of Africa. While these weren't likely to have contributed to the modern human lineage, they suggest that environmental factors that could have produced a bottleneck were unlikely to be global.

 

Two other notable events around this period can be viewed as consistent with a bottleneck. One is that two chromosomes found in chimpanzees and other apes have fused to form a single larger chromosome in the human lineage. This is estimated to have occurred around this time, and a small population would have allowed this variant chromosome to have spread to our entire lineage more readily.

 

A second is that molecular evidence suggests Neanderthals and Denisovans split off from our lineage shortly after the bottleneck was relieved. The release of whatever environmental pressure that kept populations small may have also allowed some of our ancestors to expand to new habitats and form distinct populations.

 

So, the idea of a bottleneck on the human lineage is certainly compelling. But it's likely to require additional evidence beyond the output of a single algorithm before it's widely accepted. Fortunately, there are a lot of routes to that evidence, from fossil hunting to genome sequencing to algorithm development. So, hopefully, we won't have to wait too long to get a clearer picture.

 

Science, 2023. DOI: 10.1126/science.abq7487  (About DOIs).

 

August was an eventful month for driverless taxis in San Francisco. On August 10, the California Public Utilities Commission voted to allow Google’s Waymo and GM’s Cruise to begin charging customers for driverless taxi rides across the city. A week later, Cruise vehicles were involved in two serious crashes within hours of one another. The next day, the California Department of Motor Vehicles demanded that Cruise cut its driverless taxi fleet in half while these crashes were investigated.

 

A few days later, New York Times reporter Cade Metz appeared on the Times’s flagship podcast, The Daily, to discuss these developments and the state of the self-driving industry.

 

Metz argued that in recent weeks, it has become “more and more clear to the people riding the cars, and to other citizens in the city, that they are flawed, that they do make mistakes, that they can gum up traffic, that they can cause accidents.”

 

Of course self-driving cars are flawed—all technologies are. The important question is whether self-driving cars are safer than human-driven cars. And here Metz proclaimed ignorance.

 

“We don't know yet whether it's safer than a human driver,” he said.

 

But we actually do know a fair amount about the safety of driverless taxis. Waymo and Cruise have driven a combined total of 8 million driverless miles (a Waymo spokeswoman told me the company has completed more than 4 million driverless miles, and Cruise has said the same). That includes more than 4 million in San Francisco since the start of 2023. And because California law requires self-driving companies to report every significant crash, we know a lot about how they’ve performed.

 

For this story, I read through every crash report Waymo and Cruise filed in California this year, as well as reports each company filed about the performance of their driverless vehicles (with no safety drivers) prior to 2023. In total, the two companies reported 102 crashes involving driverless vehicles. That may sound like a lot, but they happened over roughly 6 million miles of driving. That works out to one crash for every 60,000 miles, which is about five years of driving for a typical human motorist.

 

These were overwhelmingly low-speed collisions that did not pose a serious safety risk. A large majority appeared to be the fault of the other driver. This was particularly true for Waymo, whose biggest driving errors included side-swiping an abandoned shopping cart and clipping a parked car’s bumper while pulling over to the curb.

 

Cruise’s record is not impressive as Waymo’s, but there’s still reason to think its technology is on par with—and perhaps better than—a human driver.

 

Human beings drive close to 100 million miles between fatal crashes, so it will take hundreds of millions of driverless miles for 100 percent certainty on this question. But the evidence for better-than-human performance is starting to pile up, especially for Waymo. It’s important for policymakers to allow this experiment to continue because, at scale, safer-than-human driving technology would save a lot of lives.

Waymo’s impressive safety record

 

Back in February, Waymo released a report celebrating its first million miles of fully driverless operation, which mostly occurred in the suburbs of Phoenix. Waymo’s autonomous vehicles (AVs) experienced 20 crashes during those first million miles. Here are some representative examples:

 

• “A passenger car backed out of a parking space and made contact with the Waymo AV.”
• “An SUV backed out of a driveway and made contact with the Waymo AV.”
• “The vehicle that had been previously stopped behind the Waymo proceeded forward, making contact with the rear bumper of the Waymo AV.”
• “A passenger car that had been stopped behind the Waymo AV passed the Waymo AV on the left. The passenger car’s rear passenger side door made contact with the driver side rear of the Waymo AV.”

 

In short, these were mostly low-speed collisions initiated by the other diver.

 

There were only two cases where a Waymo ran into another vehicle. In one, a motorcyclist in the next lane lost control and fell off their bike. The driverless Waymo slammed on its brakes but couldn’t avoid hitting the now-riderless motorcycle at 8 miles per hour. In the other case, another vehicle cut in front of the Waymo, and the AV braked hard but couldn’t avoid a collision.

 

There were two crashes that Waymo thought were serious enough for inclusion in a federal crash database. The more serious of these was when another driver rear-ended a Waymo while looking at their phone.

 

One of Waymo’s biggest challenges during its first million miles was avoiding inanimate objects. Waymo vehicles bumped into a construction pylon, a parking lot barrier arm, and a shopping cart—all at speeds of between 8 and 13 miles per hour. Clearly, Waymo needs to do a better job of recognizing irregularly shaped objects like these. But when it comes to interacting with other vehicles, Waymo had a basically spotless driving record over those first million miles.

 

Now let’s look at how Waymo has done in San Francisco since the start of 2023. Waymo is still struggling to avoid inanimate objects. Its vehicles collided with cardboard road debris and a chain connecting a sign to a temporary pole. A Waymo also drove into a pothole that was big enough to puncture a tire. And there were two incidents where Waymos scraped parked vehicles. That’s a total of five crashes where the Waymo vehicle was clearly at fault.

 

The rest of Waymo’s driverless crashes in San Francisco during 2023 do not seem to have been Waymo’s fault. I count 11 low-speed crashes where another vehicle rear-ended a Waymo, backed into a stopped Waymo, or scraped a stopped Waymo while trying to squeeze by. There was also an incident where a Waymo got sideswiped by another vehicle changing lanes.

 

Waymo had two more serious crashes in San Francisco this year:

 

• A driverless Waymo was trying to turn left, but another car “proceeded into the intersection from the left and made contact with the left side of the Waymo AV.”
• An SUV rear-ended a Waymo hard enough that the passenger in the Waymo reported injuries.

 

I should also mention the Waymo crash that killed a dog back in May. I didn’t mention this earlier because I’ve been focusing on driverless vehicles and the Waymo that hit the dog had a safety driver behind the wheel. But this crash is worth mentioning since it’s one of the most serious ones Waymo has experienced.

 

In an emailed statement, Waymo said that it “reviewed the event from many different perspectives” and concluded there was no way either Waymo’s software or a human driver could have avoided hitting the dog. Waymo hasn’t provided the public with enough information to verify this claim, but I hope California regulators check Waymo’s work if they haven’t done so already.

We don’t have great data on the safety of human drivers

To sum up, Waymo’s driverless fleet has experienced:

 

• 17 low-speed collisions where another vehicle hit a stationary Waymo
• 9 collisions where another vehicle rear-ended a Waymo
• 2 collisions where a Waymo got sideswiped by another vehicle
• 2 collisions where a Waymo got cut off and wasn’t able to brake quickly enough
• 2 low-speed collisions with stationary vehicles
• 7 low-speed collisions with inanimate objects like shopping carts and potholes

 

There are two things to notice about this list. First, other vehicles ran into Waymos 28 times, compared to just four times a Waymo ran into another vehicle (and Waymo says its vehicle got cut off in two of these cases). Second, Waymo was only involved in three or four “serious” crashes, and none of them appear to have been Waymo’s fault.

 

This is impressive because these statistics reflect more than 2 million miles of driving (a Waymo spokeswoman told me the company has logged more than 1 million miles in San Francisco since the start of 2023). The National Highway Traffic Safety Board estimates that there are around 6 million car crashes reported to the police each year. Americans drive around 3 trillion miles per year, so roughly speaking, a “major” crash occurs on the roads once every 500,000 miles.

 

Most crashes involve two vehicles. So if Waymo’s vehicles drove as well as a typical human driver, you’d expect it to be involved in around eight serious crashes over 2 million miles of driving.

 

It’s important to emphasize that there’s a lot of uncertainty about these figures.

 

“We know very little about the safety of our roads,” the legal scholar Bryant Walker Smith told me. “If we're looking at just crashes, given how little information is carefully collected and studied, we don't have any sense of the circumstances of these low-level crashes.”

 

Not all crashes—even serious ones—are reported to the police.

 

Moreover, Smith said, “these companies are not driving a representative sample of miles.”

 

Both Waymo and Cruise have their driverless cars avoid freeways, which tend to have fewer crashes per mile of driving. Both companies are active in San Francisco, which has more chaotic streets than most US cities.

 

On the other hand, a small minority of drivers—including teenagers, elderly people, and drunk drivers—account for a disproportionate share of crashes. An alert and experienced driver gets into crashes at a rate well below the national average. So if we want AVs to drive as well as an alert and experienced driver, we'll want to set the bar higher than the national average.

 

With all that said, it seems that Waymo cars get into serious crashes at a significantly lower rate than human-driven cars. I’ll have more to say about this after we look at Cruise’s safety record.

Cruise has room for improvement

 

Cruise released a report back in April about its first million driverless miles. The company reported 36 crashes, compared to 20 for Waymo’s first million driverless miles. I wouldn’t put too much stock into that difference, since Cruise was operating mainly in San Francisco, a more chaotic driving environment than the Phoenix suburbs where Waymo started out.

 

So far in 2023, Cruise has filed an additional 27 crash reports related to its fully driverless cars. What follows is a summary of all 63 crashes Cruise reported through August 25. I’ll also count a widely publicized August 17 crash with a fire truck even though there’s still no report on this crash on the website of the California Department of Motor Vehicles.

 

Like Waymo, Cruise has had trouble with its vehicles hitting inanimate objects. Two Cruise vehicles ran into downed power cables. Cruise vehicles also ran into a scooter (without someone on it), a tow dolly on the back of a double-parked truck, a “motorized articulating boom lift,” and a pothole. The pothole punctured a tire, causing the Cruise AV to swerve into a parked car.

 

Cruise has also experienced a large number of low-speed crashes where another vehicle (including a scooter in one case and a skateboarder in another) either rear-ended a Cruise AV, backed into one at low speeds, or scraped the side of a Cruise while trying to pass it.

 

There were also a few rare situations:

 

• A Cruise vehicle was “stuck in a sideshow event and stationary with vehicles driving around it on either side.” (A sideshow is an illegal late-night show where young people perform donuts and other stunts in an intersection.) One of the other cars ran into the Cruise AV.
• An Infinity Q50 was “performing donuts” in an intersection before crashing into a Cruise vehicle.
• A driver drove the wrong way down a one-way street while staring at a phone. The car hit a stopped Cruise vehicle facing the right way.

 

There were about a dozen side-swipe events where another vehicle either ran into the Cruise AV from the side during a lane change or tried to make a turn from a middle lane, crossing the path of the Cruise AV. Most of these crashes occurred during Cruise’s first million miles, so Cruise may be getting better at handling these situations.

 

It’s important to note that Cruise has logged more than four million miles in San Francisco, so Cruise’s crash reports represent roughly twice as many miles as Waymo’s. Once you adjust for that, Waymo and Cruise seem to have been involved in low-stakes crashes at similar rates.

 

For example, Cruise vehicles got rear-ended 17 times over about 4 million miles, while Waymo vehicles got rear-ended seven times over roughly 2 million miles. That makes sense given that Cruise drove twice as many miles and that Waymo logged almost half of its miles in the tame Phoenix suburbs.

 

But even taking those differences into account, there are a couple areas where Cruise’s performance does not seem to be on par with Waymo.

 

One is significant crashes where Cruise was clearly at fault. I saw three examples of this:

 

• A Cruise AV mistakenly thought the vehicle ahead of it was starting to turn left. The Cruise ran into the other vehicle when it turned right instead.
• A Cruise AV changed lanes when there wasn’t enough space to do so, cutting off another vehicle and leading to a crash.
• A Cruise AV ran into the back of a city bus. Cruise subsequently determined that its software got confused because it was an articulated bus (the kind with an accordion joint in the middle) and Cruise’s software couldn’t handle two parts of a vehicle moving in slightly different directions.

 

Each of these mistakes strikes me as more serious than any of Waymo’s mistakes (recall that all of Waymo’s clearly at-fault crashes were low-speed collisions with inanimate objects or parked vehicles).

Cruise might have a problem with intersections

 

Cruise’s other trouble spot is intersections. Cruise says two bicyclists have run stop signs and crashed into Cruise vehicles. And there have been five vehicles that ran red lights and crashed into Cruise vehicles:

 

• This Mercedes sedan
• This Volkswagen hatchback
• This Infinity Q60
• This Dodge Charger
• This fire truck with its sirens blaring

 

A passenger in that last Cruise AV was taken to the hospital; Cruise described their injuries as “non-severe.”

 

Perhaps all of these crashes (with the possible exception of the fire truck) were the fault of the other drivers (and cyclists). Still, it’s interesting that over two million miles of driverless operation, no Waymo AVs got hit by cars running red lights or bicycles running stop signs.

 

Again, this may be partly because Cruise has driven more miles—and especially more miles in San Francisco. Also, Cruise has largely operated at night, when there might be more impaired drivers on the road.

 

But I think there might be something else going on here.

 

A couple of years ago, Waymo published research exploring the potential for self-driving cars to prevent crashes by anticipating the reckless behavior of other drivers. Waymo researchers obtained detailed records about fatal crashes that occurred in and around the Phoenix suburb of Chandler (where Waymo launched its first driverless taxi service). Waymo then hired an independent engineering firm to create detailed digital reconstructions of these crashes. Then the company loaded this data into its simulator to explore how Waymo’s self-driving software would have reacted in the seconds preceding each crash.

 

Waymo found its software could prevent every crash if it took the role of the “initiator,” the vehicle whose erratic behavior set the crash in motion. More surprisingly, Waymo also found its software could prevent 82 percent of crashes playing the role of the other driver.

 

The most common setting for fatal crashes in this data set was intersections—including a number of vehicles running red lights. Waymo found that when its software played the role of the “other driver,” it was able to avoid crashes in 81 percent of scenarios at intersections.

 

In the wake of the Cruise collision with a fire truck on August 17, Waymo told industry analyst Brad Templeton that its vehicles would have handled the situation better than Cruise did:

 

When we hear sirens, our vehicle will slow and then depending on how the situation develops, we will either pull over or stop ahead of intersections where there might be crossing emergency vehicles, even if we have a green light. The system is designed to remain cautious and not enter an intersection if it is still reasoning whether the emergency vehicle is approaching the intersection based on what it is sensing.

 

I think technology like this may explain why Waymo has been successful at avoiding major crashes at intersections. Not only do Waymo’s vehicles follow the letter of the law (like stopping at red lights), they may also try to anticipate and avoid dangerous situations (like vehicles running red lights).

 

Cruise vehicles do not seem especially cautious about intersections. For example, a Reddit user posted a video from August 22 showing a Cruise vehicle crossing an intersection several seconds after the opposing traffic got a green light. Cruise says its vehicle was already in the intersection when its light turned red so the vehicle didn’t break the law. Maybe that’s technically true—I’m not an expert on California traffic law. But I’m pretty sure it would have been safer for the car to stay where it was and wait for the next green light.

Cruise’s technology is pretty good, but Waymo’s is better

 

The bottom line is that I’m convinced that Waymo vehicles drive more safely than Cruise vehicles. This isn’t surprising; Waymo started its life as the Google self-driving project several years before Cruise was founded. Back in 2020, Waymo announced it had completed 20 million miles of on-road testing (almost all of them with safety drivers). The same year, Cruise reached 2 million miles.

 

In short, Waymo has invested more time and resources into its technology. It would be surprising if all that extra work didn’t yield superior performance. With that said, I don’t want to be too negative about Cruise. Because while the company’s technology doesn’t seem to be as good as Waymo’s, it’s still pretty good.

 

Earlier, I discussed why it’s so difficult to develop a good benchmark for human driving performance. We only know about crashes that get reported to the police or other authorities, giving us a patchy understanding of how many crashes really occur.

 

Cruise tried to address this problem by hiring a team of prominent academic researchers to study the driving behavior of ride-hail drivers in San Francisco. The researchers examined 5.6 million miles of data and concluded that collisions involving San Francisco ride-hail drivers occur about once every 20,000 miles. That includes a lot of minor crashes that wouldn’t be reported to police.

 

Based on this data, Cruise claimed that over its first million miles, its vehicles crashed 56 percent less often per mile than a typical human driver. Moreover, Cruise estimated that its cars were 73 percent less likely to be in a crash with a risk of a serious injury and 93 percent less likely to be the “primary contributor” to a crash.

 

One should take these conclusions with a grain of salt given that the research was commissioned by Cruise. But they don’t seem crazy. Cruise vehicles really do seem to crash into other vehicles much less often than vice versa. So I wouldn’t be surprised if Cruise vehicles already drive more safely than the average human driver.

The need for real-world testing

The big question for policymakers is whether to allow Waymo and Cruise to continue and even expand their services. This should be an easy call with respect to Waymo, which seems to be safer than a human driver already. The faster Waymo scales up, the more crashes can be prevented.

 

I think Cruise’s tech is probably safer than a human driver too, but it’s a closer call. I could imagine changing my mind in the coming months as more data comes in.

 

Still, it’s important to remember that access to public roads is essential for testing and improving self-driving technology. This is not a technology Waymo or Cruise can meaningfully test “in the lab.” The companies need exposure to the full complexity of real public streets in order to make progress. And given that both companies are likely to eventually develop products that are much safer than human drivers, slowing down the development of the technology could easily cost more lives than it saves.

 

So while the DMV’s decision to cut the size of Cruise’s fleet in the wake of the August 17 crashes was understandable, I hope the decision is short-lived. Ultimately the only way for Cruise to improve its technology is by testing it on public roads. And we’ll all benefit from the widespread availability of self-driving cars that are dramatically safer than human drivers.

 

One easy way for policymakers to improve safety—or at least accountability—would to require self-driving companies to be more even more transparent about their safety records. This story relied heavily on California’s excellent website that publishes all of the Waymo and Cruise crash reports. I’d love for the California Department of Motor Vehicles to go a step further and require self-driving companies to submit video footage of the seconds before and after each crash. That way, members of the public could evaluate whether companies’ descriptions of crashes are accurate.

 

It would also be very helpful for regulators in other states—or perhaps federal officials—to require the same kind of crash reporting that they have in California. For example, Waymo is running a substantial driverless taxi service in Phoenix, but we know very little about how well Waymo's AVs have performed there in recent months. More transparency here and in other states could help to build public trust.

 

Tim Lee was on staff at Ars from 2017 to 2021. He recently launched a new newsletter, Understanding AI. It explores how AI works and how it's changing our world. You can subscribe to his newsletter here.

 

A view of India's Vikram lander taken Wednesday from the Pragyan rover.

 

It's been more than a week since India's Chandrayaan 3 mission landed on the Moon, and it's a good time to assess where the world's most populous nation stands relative to other global other space powers.

 

The successful arrival of the Chandrayaan 3 mission's Vikram lander on the Moon made India the first country besides China to achieve a soft landing on the lunar surface since 1976, following a series of failed landings by private organizations and India itself four years ago. And it made India just the fourth nation overall to achieve this feat.

 

Since the landing of Chandrayaan 3on August 23, India has released some early findings from the lander and its mobile rover, named Pragyan, along with photos of the vehicles exploring the Moon's alien charcoal-colour landscape.

 

The Moon landing is just the latest in a string of successes in space for India, which has a thriving rocket program with a family of four launch vehicles, its own regional satellite navigation network, and nearly 10 years ago, sent an orbiter to Mars. If India can notch another success in its space program in the next few years, the country could become the fourth nation capable of sending its astronauts into low-Earth orbit.

 

India is still well behind the space programs of the United States and China, but one could argue India has moved closer to Europe and Russia, and could be on par with Japan when you take into account several factors: access to space, space exploration, military space projects, and applications like communications, navigation, and remote sensing from orbit.

 

Among the space powers considered here, India has the lowest human development index, a measure of social factors such as quality of life, income, and education. But its space program is a point of national pride, and Narendra Modi, India's nationalist prime minister, has made a point to associate himself with Indian successes in space.

 

Those successes have come on a shoestring budget. The Indian government this year is allocating $1.52 billion to space efforts, and India developed and launched Chandrayaan 3 for less than $100 million, lower than the cost of many blockbuster Hollywood films.

 

“I’ve described India as a sleeping giant and one that is quickly awakening," said Mike Gold, an attorney and space industry official who previously led NASA's space policy office. "India is absolutely vital to global space development ... since the country is active with lunar programs, Martian programs, and now even human spaceflight.”

 

Since the landing of Chandrayaan 3, the Indian Space Research Organization (ISRO)—India's space agency—has released a handful of images, including a black-and-white shot of the stationary SUV-size Vikram lander taken by the Pragyan rover. There's also a video, shown below, of the Pragyan rover rolling down the ramp from the Vikram lander in the hours after arriving on the Moon on August 23.

 

 

So far, ISRO hasn't been releasing all of the pictures taken by the rover and lander on the Moon, and the Indian space agency hasn't posted many images on its website, preferring to share them on social media. Let's hope Indian officials develop a better way of releasing high-resolution imagery from Chandrayaan 3 and future deep space probes.

 

But it's always exciting to see a place human eyes have never seen before, and India's triumph with Chandrayaan 3 is worth celebrating.

 

In a visit with Indian space scientists in Bangalore last week, Modi announced the Chandrayaan 3 landing site would be named Shiv Shakti Point, a reference to Shiva, a principal deity in Hinduism, and Shakti, which honors the role of women scientists on the mission.

 

The Vikram lander and Pragyan rover settled onto a landing site closer to the Moon's south pole than any previous lunar lander. Early science results from the mission include the detection of a seismic "event" on the Moon, and the first measurements of the plasma environment near the lunar surface close to the south pole.

 

"These quantitative measurements potentially assist in mitigating the noise that lunar plasma introduces into radio wave communication. Also, they could contribute to the enhanced designs for upcoming lunar visitors," ISRO said.

 

Instruments on the rover have detected sulfur in the lunar crust at the landing site. "This finding ... compels scientists to develop fresh explanations for the source of sulfur in the area," ISRO said, adding that the element could be intrinsic to the landing site, or may have been produced by an ancient volcanic eruption or an asteroid or cometary impact.

 

The Times of India reported this week that Indian engineers are increasingly optimistic that the Vikram lander and Pragyan rover could wake up and continue their mission after the upcoming two-week-long lunar night. When the Sun sets at the landing site next week, the two vehicles will hibernate as temperatures plummet to minus 333° Fahrenheit (minus 203° Celsius).

 

The original design life of the lander and rover was to operate for one lunar day, or 14 Earth days, but assuming electronics and batteries hold up to the frigid conditions, there's a chance the vehicles will automatically wake up when rays of sunlight again fall on their solar panels in mid-September.

Taking India seriously

The landing follows several decades of serious growth in India's accomplishments in space. India launched a small satellite into low-Earth orbit with an indigenous rocket for the first time in 1980, then debuted the workhorse Polar Satellite Launch Vehicle in 1993.

 

India's orbital-class rockets only flew about one time per year until the early 2000s. Since then, India has ramped up its launch rate, reaching seven orbital flights on a couple of occasions, an annual record that India is poised to shatter this year. The country has launched its rockets six times so far in 2023, with a seventh launch scheduled for Saturday.

 

Those recent launch statistics fall far behind the United States, China, and Russia. In terms of mass launched into orbit, ISRO ranked fourth among global launch providers in the first half of this year, after SpaceX, China's state-run launch enterprises, and Russia's space agency, according to data released by BryceTech.

 

India's expendable rockets have notched 54 successful launches in 57 tries since 2011—a success rate of nearly 95 percent, about the same as all European and Japanese rockets and slightly better than Russian launch vehicles in the same period. India's 95 percent success rate falls short of the reliability of US launch companies SpaceX and United Launch Alliance, and also lags behind China's Long March rocket family.

 

 

India's launch vehicles are regularly used to deploy the country's satellites and payloads from international and commercial customers. When OneWeb could no longer launch its Internet satellites on Russian rockets after the invasion of Ukraine, the company selected SpaceX and India's heaviest rocket, the LVM3, to finish launching the broadband network.

 

ISRO recently started an initiative to commercialize its rockets by turning over responsibility for manufacturing and launch operations to the private sector.

 

Launch is just one way of assessing the standing of India's space program on the global stage. India has dispatched robotic missions to orbit Mars, orbit the Moon, and now land on the Moon, vaulting ISRO into an exclusive club of space agencies. These achievements in planetary science are comparable to those of the European Space Agency and JAXA, Japan's space agency. Although those space agencies haven't landed on the Moon—and Japan hasn't had a successful mission to Mars—ESA and JAXA have had more success in sending probes to comets and asteroids.

 

In this area, India is indisputably ahead of Russia in terms of recent accomplishments. Russia hasn't had a successful mission to another celestial body since the Soviet era in the 1980s.

 

India and Japan are working together on a future robotic lunar landing mission that could launch in the late 2020s, and India in June signed on to the Artemis Accords, a non-binding set of principles among like-minded nations guiding a vision for peaceful and transparent exploration of space. The Artemis Accords were developed by the United States, and the signing raised questions about future Indian partnership with NASA's Artemis lunar program, although US and Indian officials haven't laid out any details of potential cooperation.

 

“The fact that they are a nation that intends in the future to fly their own astronauts, is that significant? The answer is yes,” said NASA Administrator Bill Nelson in a conversation with Ars in June. “I think it’s of significance that a major country that’s not considered aligned with the US (is) a signatory.”

 

Tracks from the Pragyan rover on the surface of the Moon.

 

Another milestone mission for India's space program is scheduled for launch on Saturday, when a PSLV rocket is set for liftoff with a solar observatory named Aditya-L1. This spacecraft will travel to an orbit around the L1 Lagrange point nearly a million miles (1.5 million kilometers) on the Sunward side of the Earth, where Aditya-L1 will use a solar telescope and coronagraph to observe the Sun and a suite of sensors to measure the solar wind.

 

Next year, an Indian rocket will send a sophisticated radar satellite into orbit in partnership with NASA to measure minute changes on Earth's surface.

 

Then there is the proliferation of Indian satellites circling Earth, ranging from television broadcast satellites to sharp-eyed reconnaissance spacecraft feeding data to India's military. India also has a network of satellites providing navigation services over South Asia, a similar regional capability to one that Japan has deployed over the last decade. The United States, China, and Russia each have their own satellite networks for global navigation services.

Where is India lagging?

Barring any significant delays, India is a few years away from truly entering the uppermost echelons of the world's space powers. The $1.1 billion Gaganyaan program (Gaganyaan means "celestial vehicle" in Sanskrit) has been a priority of Prime Minister Modi, who announced in 2018 that the new Indian-made space capsule would carry an Indian astronaut into orbit by 2022.

 

That timetable has come and gone, and the first crewed flight of the Gaganyaan spacecraft is now projected to occur no earlier than 2025. But some big milestones are on the horizon, with a high-altitude test of the Gagayaan launch abort system planned as soon as late September or early October. An on-pad test of the abort system occurred in 2018.

 

An orbital test flight of the Gaganyaan spacecraft without any crew members aboard could launch in 2024, setting the stage for the astronaut flight in 2025.

 

As a prelude to the Gaganyaan program, NASA and ISRO have agreed to train Indian astronauts at the Johnson Space Center in Houston, and an Indian crew member will fly to the International Space Station next year on a short-duration mission. Four Indian astronauts slated for the Gaganyaan program completed more than a year of training at Russia's Gagarin Cosmonaut Training Center near Moscow in 2021, according to Indian media.

 

 

India is human-rating its LVM3 rocket, with two powerful solid rocket boosters and a liquid-fueled core stage, to haul the Gaganyaan spacecraft into orbit. The capsule is designed to accommodate a crew of three astronauts for missions lasting up to one week.

 

If India successfully establishes a sustainable human spaceflight program, then it may be time to re-evaluate India's ranking relative to Russia among space-faring nations. Despite Russia's languishing record in deep space exploration, its prowess in human spaceflight continues to make Russia's space program a global leader.

 

Russia's venerable Soyuz spacecraft used for crew missions still relies on a design originating more than 50 years ago, but the Soyuz has flown more missions than any other human-rated spacecraft. Russia has committed to ferrying crews to and from the International Space Station through at least 2028, but there are fundamental questions about what comes next for Russia's human spaceflight program.

 

Russia's space agency has unveiled a concept for a national space station to take over from the ISS, but new Russian space projects that aren't rooted in the designs of the Soviet era have had little success.

 

India also has some catching up to do in its military space program to match the capabilities of the United States, China, Russia, and the collective capacity of European nations. Likewise, India's expertise in rocket propulsion falls behind other countries.

 

For the most part, India's rockets are powered by solid-fueled motors and liquid-fueled engines using hypergolic propellants. These engines consume toxic hydrazine and nitrogen tetroxide, a propellant mix that the United States and Russia are moving away from with their large rockets.

 

Hypergolic propellants are easier to handle than cryogenic fuels, and they come with a benefit in their simplicity. Hypergolic fluids combust when they come into contact with one another, meaning the only thing that needs to happen for an engine to ignite is the opening of propellant valves.

 

India uses the liquid-fueled Vikas engine on its three largest rockets, including the new LVM3 that will launch the Gaganyaan crew spacecraft. The Vikas engine is based on the French Viking engine, which was developed in the 1970s for the European Ariane rocket. India has a cryogenic hydrogen-fueled upper-stage engine that flies on the LVM3, but there aren't any other engine development projects far enough long to be ready for flight in the next few years.

 

Russia, on the other hand, still boasts an impressive pedigree in rocket propulsion, good enough to find customers in the international market, including in the United States. Its kerosene-fueled staged combustion engines have a perfect record flying on ULA's Atlas V and Northrop Grumman's Antares rockets.

 

China's newest generation of Long March rockets are powered by engines that consume cryogenic propellants and will eventually replace the older line of Long March rockets using hypergolic propellants.

 

Of course, the United States is a world leader in rocket propulsion, with a wide array of high-thrust engines that burn kerosene, hydrogen, and methane.

 

There’s a lot of trash on the Moon right now—including nearly 100 bags of human waste—and with countries around the globe traveling to the Moon, there’s going to be a lot more, both on the lunar surface and in Earth’s orbit.

 

In August 2023, Russia’s Luna-25 probe crashed into the Moon’s surface, while India’s Chandrayaan-3 mission successfully landed in the southern polar region, making India the fourth country to land on the Moon.

 

 

With more countries landing on the Moon, people back on Earth will have to think about what happens to all the landers, waste, and miscellaneous debris left on the lunar surface and in orbit.

 

I’m a professor of astronomy who has written a book about the future of space travel, articles about our future off-Earth, conflict in space, space congestion, and the ethics of space exploration. Like many other space experts, I’m concerned about the lack of governance around space debris.

Space is getting crowded

People think of space as vast and empty, but the near-Earth environment is starting to get crowded. As many as 100 lunar missions are planned over the next decade by governments and private companies like SpaceX and Blue Origin.

 

Near-Earth orbit is even more congested than the space between Earth and the Moon. It’s from 100 to 500 miles straight up, compared with 240,000 miles to the Moon. Currently there are nearly 7,700 satellites within a few hundred miles of the Earth. That number could grow to several hundred thousand by 2027. Many of these satellites will be used to deliver Internet to developing countries or to monitor agriculture and climate on Earth. Companies like SpaceX have dramatically lowered launch costs, driving this wave of activity.

 

“It’s going to be like an interstate highway, at rush hour in a snowstorm, with everyone driving much too fast,” space launch expert Johnathan McDowell told Space.com.

The problem of space junk

All this activity creates hazards and debris. Humans have left a lot of junk on the Moon, including spacecraft remains like rocket boosters from over 50 crashed landings, nearly 100 bags of human waste, and miscellaneous objects like a feather, golf balls, and boots. It adds up to around 200 tons of our trash.

 

Since no one owns the Moon, no one is responsible for keeping it clean and tidy.

 

The clutter in Earth’s orbit includes defunct spacecraft, spent rocket boosters, and items discarded by astronauts, such as a glove, a wrench, and a toothbrush. It also includes tiny pieces of debris like paint flecks.

 

There are around 23,000 objects larger than 10 cm (4 inches) and about 100 million pieces of debris larger than 1 mm (0.04 inches). Tiny pieces of junk might not seem like a big issue, but that debris is moving at 15,000 mph (24,140 kph), 10 times faster than a bullet. At that speed, even a fleck of paint can puncture a spacesuit or destroy a sensitive piece of electronics.

 

The amount of debris in orbit has increased dramatically since the 1960s.

 

In 1978, NASA scientist Donald Kessler described a scenario where collisions between orbiting pieces of debris create more debris, and the amount of debris grows exponentially, potentially rendering near-Earth orbit unusable. Experts call this the “Kessler syndrome.”

Nobody is in charge up there

The United Nations Outer Space Treaty of 1967 says that no country can “own” the Moon or any part of it and that celestial bodies should only be used for peaceful purposes. But the treaty is mute about companies and individuals, and it says nothing about how space resources can and can’t be used.

 

The United Nations Moon Agreement of 1979 held that the Moon and its natural resources are the common heritage of humanity. However, the United States, Russia, and China never signed it, and in 2016 the US Congress created a law that unleashed the American commercial space industry with very few restrictions.

 

Because of its lack of regulation, space junk is an example of a “tragedy of the commons,” where many interests have access to a common resource, and it may become depleted and unusable to everyone, because no interest can stop another from overexploiting the resource.

 

Scientists argue that to avoid a tragedy of the commons, the orbital space environment should be seen as a global commons worthy of protection by the United Nations. The lead author of a Nature article arguing for a global commons filed an amicus brief—a type of outside comment offering support or expertise—on a case that went to the US Court of Appeals for the District of Columbia Circuit in late 2021.

 

The author and his research collaborators argued that US environmental regulations should apply to the licensing of space launches. However, the court declined to rule on the environmental issue because it said the group lacked standing.

 

National geopolitical and commercial interests will likely take precedence over interplanetary conservation efforts unless the United Nations acts. A new treaty may emerge from the work of the UN Office for Outer Space Affairs, which in May 2023 generated a policy document to address the sustainable development of activities in space.

 

The UN can regulate the activities of only its member states, but it has a project to help member states craft national-level policies that advance the goals of sustainable development.

 

NASA has created and signed the Artemis Accords, broad but nonbinding principles for cooperating peacefully in space. They have been signed by 28 countries, but the list does not include China or Russia. Private companies are not party to the accords either, and some space entrepreneurs have deep pockets and big ambitions.

 

The lack of regulation and the current gold rush approach to space exploration mean that space junk and waste will continue to accumulate, as will the related problems and dangers.

 

Chris Impey is University Distinguished Professor of Astronomy at the University of Arizona.

Scientists have been working on models of planet formation since before we knew exoplanets existed. Originally guided by the properties of the planets in our Solar System, these models turned out to be remarkably good at also accounting for exoplanets without an equivalent in our Solar System, like super Earths and hot Neptunes. Add in the ability of planets to move around thanks to gravitational interactions, and the properties of exoplanets could usually be accounted for.

 

Today, a large international team of researchers is announcing the discovery of something our models can't explain. It's roughly Neptune's size but four times more massive. Its density—well above that of iron—is compatible with either the entire planet being almost entirely solid or it having an ocean deep enough to drown entire planets. While the people who discovered it offer a couple of theories for its formation, neither is especially likely.

A freakish outlier

The study of the new planet started as many now do: It was identified as an object of interest by the Transiting Exoplanet Survey Satellite (TOI, for TESS Object of Interest). TOI-1853 is a star somewhat smaller than our Sun, with about 0.8 times its mass. And there were clear indications of a planet near the star, now called TOI-1853 b. The planet orbits quite close to its host star, completing a full orbit in 1.24 days.

 

The researchers used that time to determine the distance at which the planet orbits. Based on a combination of that distance, the size of the star, and the amount of light blocked by the planet, it's possible to estimate the planet's size. That turned out to be about 3.5 times Earth's radius, meaning it's a bit smaller than Neptune.

 

On its own, that's not unusual; many Neptune-sized planets have been discovered. But the combination of size and proximity to the star is unexpected. It places it in what's called the "hot Neptune desert," where intense radiation from the star drives off a planet's atmosphere. Neptunes that reach the hot desert state end up stripped down to their rocky cores, which leaves them as super-Earths.

 

So what was TOI-1853 b doing in the desert? To find out, the researchers used ground-based observatories to track the movement of its host star as the gravitational pull of TOI-1853 b shifted as it moved through its orbit. The acceleration in the star's motion due to this pull can be used to estimate the planet's mass.

 

It turned out that TOI-1853 b has a lot of mass. It's estimated to be 73 times the mass of Earth or over four times the mass of Neptune. Pretty clearly, that means its composition must be very different from Neptune's.

Crunchy on the inside and outside?

The researchers involved in its discovery spend a fair bit of text describing just how much of an outlier this makes TOI-1853 b. There are planets with similar densities, but they're typically significantly smaller—the super-Earths formed by stripping away the atmosphere on a Neptune-like planet. There are planets with similar masses, but they're almost all twice as large and are likely to have extensive atmospheres and/or oceans. "It occupies a region of the mass–orbital [distance] space of hot planets that was previously devoid of objects, corresponding to the driest area of the hot-Neptune desert," the researchers conclude.

 

The oddities don't end there. There are two compositions that make sense given the densities at play here. One has the planet being almost entirely composed of rocky material like Earth's, with an extremely thin atmosphere that accounts for one percent of its mass at most. The alternative is that the mass is evenly distributed between a rocky core and an immense coating of water.

 

Of course, that wouldn't be water as we know it. Given its proximity to its host star and the massive pressures from that much ocean, at least some of that water would be in a supercritical state, and the pressure near the rocky core would force water to form high pressure solids. Things would be equally weird inside the core. As the researchers note, "The properties of matter at such high central pressures are still uncertain."

 

Not only do we struggle to understand its present, but we're at a bit of a loss when it comes to its past. Accumulation of small dust particles from the planet-forming disk would shut off before TOI-1853 b reached its present mass, as even a smaller planet would disrupt the disk. And it is unlikely to have formed in its current location, given that solids have difficulty condensing there.

Two possibilities, neither likely

The researchers suggest two possibilities. One is that a group of smaller planets formed further out and then had their orbits destabilized as the disk gradually evaporated. This could have resulted in collisions that shattered several planets, which then saw their debris form a single body. But these processes don't tend to form single bodies, and it would probably take a lot of planets to carry 73 Earth's worth of materials.

 

The alternative is that several gas giants formed much further out and then destabilized each other's orbits, leaving one highly eccentric, with one portion of the orbit extremely close to the host star. This would allow it to gather material from the inner portions of the planet-forming disk, a process that could allow a Jupiter-like planet to roughly double in mass. Its extreme orbit would also allow it to transfer its atmosphere to the star. After these processes were complete, tidal interactions between the planet and the star would eventually make its orbit far more regular.

 

There's nothing physically impossible about either of those potential formation mechanisms, but both require a series of unlikely events. The Universe is big, and those things probably happen somewhere, but it seems unreasonable to expect we'll stumble across their results this quickly.

 

One thing that might help us understand TOI-1853 b's origin is the presence of other planets in the system, which might help us understand what was happening in the inner portions of this exosolar system. TOI-1853 b is so big and so close that it creates an enormous signal, and we would have had trouble detecting any other planets in this system. The researchers estimate that something as massive as 10 Earths could also be orbiting close to the star, and we would have missed it. Continuing observations may be key to understanding the system.

 

Nature, 2023. DOI: 10.1038/s41586-023-06499-2  (About DOIs).

 

Amid much fanfare, SpaceX started landing its Falcon 9 rockets in 2015, and it began reusing them less than two years later. The first stage of the Falcon 9 rocket, with nine engines and the bulk of the mass, accounts for about half of the cost of manufacturing a rocket, so this represents a considerable savings in time and money for SpaceX.

 

However, as with most other boosters, there are two other main components of the Falcon 9 rocket. There is the second stage, which boosts a payload into orbit, and, for most missions, a payload fairing that protects the satellite during its transit through the atmosphere. SpaceX briefly studied recovering the second stage of the Falcon 9 but concluded it was not feasible without major modifications that would have greatly reduced the rocket's payload capacity.

 

But what about the payload fairing? These are built in two pieces through a laborious process of laying down composite materials, not dissimilar to papier-mâché. The manufacture of fairings is time-consuming, and it costs about $6 million to produce both halves.

Go and get them

Several years ago, SpaceX founder Elon Musk challenged his employees to go catch the fairings. "You have six million bucks falling from the sky," Musk famously said. But how to do it?

 

Originally, the company's engineering team reasoned that they had to catch them with a net before hitting the ocean, said Kiko Dontchev, vice president of launch at SpaceX. Dontchev spoke about the fairing-recovery effort during the "Summit At Sea" program earlier this year. A video of his talk is available on YouTube.

 

The concern among the engineers was that exposing the fairing and its delicate electronics to seawater would cause significant corrosion. This would render the fairing halves unusable, they believed. So the SpaceX engineering team developed a complex recovery process, and the company caught its first fairing in January 2020.

 

"You basically had this really awesome algorithm, this crazy automation," Dontchev said. "The fairing had a parafoil and it would steer itself, and then the boat would have this automated control that would basically turn and follow. And the two would close. And that's how you would capture them. It worked. We did it."

 

Except it didn't work with regularity, as weather out in the Atlantic Ocean was a major factor.

 

"The reality is, most of the time, it's a choppy hot mess with 7- to 9-foot waves, a super short period, and a ton of wind," Dontchev said. "So even though we caught it once, our actual success rate for bringing fairings home was quite low. It was under 50 percent, 40 percent. Our ability to get fairings ready to fly was choking our launch rate."

Simplifying the process

As part of his talk, Dontchev spoke about the "algorithm" that SpaceX uses when it designs new technology to solve problems. Essentially, it provides a roadmap for innovating.

 

"When you're fundamentally innovating a new technology, you're wrong," he said. "It's just a question of how wrong. Because your ability to learn is changing constantly. So where you start is certainly not where you're going to end up."

 

The algorithm begins with two steps: "make the requirements less dumb" and "delete the part or process step." This basically means engineers should think outside of the box and challenge existing requirements. They should then ask whether they're solving the right problem.

 

In the case of the fairings, the problem of catching them before they fell into the ocean was the wrong problem. The right problem was recovering the fairings and refurbishing them for flight as quickly as possible.

 

"What we found out is that fairings float pretty well," Dontchev said. "Like a sailboat, they're composite. It's really just a big boat. Well, do we really need to catch them? We challenged that requirement. We moved some of the sensitive parts to the higher part of the fairing." This allows for the fairing electronics to survive, even if the fairing takes on a bit of water.

Putting it all together

The SpaceX algorithm has five steps. Basically, Dontchev said, you repeat the first two steps as many times as necessary before jumping to the final three steps: optimize, accelerate, and automate.

 

With the fairings, the company finally completed step two with the ocean-based recovery. It had a far simpler system, with a standard recovery vessel and crane to fish the fairing halves out of the ocean. This allowed the company to go from a low success rate of catching fairings to a 99 percent success rate of recovery. They could be rapidly refurbished and turned around for additional launches within weeks.

 

But this created a new problem of sorts. Where to put them all?

 

"We have more fairings than we have space," Dontchev said. "Fairings are a thing we don't even come close to talking about when it's time for launch. They're always ready, no problem."