5 Years Ago, New Horizons Reached Pluto—and We Never Stopped Learning

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5 Years Ago, New Horizons Reached Pluto—and We Never Stopped Learning

Here's everything the intrepid spacecraft has taught us about the distant dwarf planet.

 

NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

 

On July 14, 2015, the New Horizons spacecraft zipped past Pluto, snapping stunning pictures of the dwarf planet and its moons. It took almost 10 years for the spacecraft, which launched on

 

January 19, 2006, to get there.

 

The flyby revealed a wealth of information about the icy world, including its bright blue atmosphere, massive nitrogen glacier, and young surface, and shed light on the nearby moons Charon, Nix,

 

and Hydra. Five years later, we celebrate nine of the groundbreaking discoveries that New Horizons made.

 

The spacecraft is still racing across our solar system and has taken detailed images of Arrokoth, a distant Kuiper Belt object. We're excited to see what the hardy instrument spies next.

 

 

Pluto's Nitrogen Glacier Is the Largest Known Glacier in the Solar System

 

Pluto's stunning Sputnik Planitia, made from nitrogen ice (compared to Earth's water ice glaciers), stretches for about 600 miles along the left lobe of the heart-shaped Tombaugh Regio region. The

 

vast flows of slow-moving ice are also crater-free, meaning they're extremely young.

 

 

 

 

There Is *Some* Water Ice on Pluto

 

New Horizons also spotted evidence of water ice on the distant world. The spacecraft's Ralph spectral composition mapper detected several regions of exposed ice near the dwarf planet's

 

Tombaugh Regio region.

 

Water ice is pretty rare, though. Researchers believe there may be more water ice buried beneath ice flows made from other elements.

 

"Understanding why water appears exactly where it does, and not in other places, is a challenge that we are digging into," science team member Jason Cook, of Southwest Research Institute, said

 

in a statement announcing the discovery.

 

 

 

 

Pluto Has Mountains As Tall As the Rockies

 

Pluto is relatively young and active. The distant world has ranges of ice mountains as high as the Rocky Mountains here on Earth. This, paired with the surprising lack of craters, suggests the dwarf

 

planet is still geologically active.

 

But what drives this cold, frigid world to be so geologically active? Could it be a subsurface ocean? Researchers are still puzzled.

 

 

 

 

 

Pluto's Atmosphere Is Escaping Into Space

 

When New Horizons swept by Pluto, it took pictures of and collected data about the dwarf planet's atmosphere. It's composed mainly of nitrogen, with traces of methane and carbon monoxide.

 

Through a process called hydrodynamic outflow, though, Pluto's nitrogen atmosphere is escaping into space at a rapid pace, according to Vox. Researchers could tell because an instrument on the

 

spacecraft captured evidence of nitrogen atoms farther away from the planet than expected.

 

 

 

 

It's Also Bright Blue!

 

Pluto's atmosphere is filled with hydrocarbon particles called tholins, which scatter sunlight and create a bright blue hue. This image was taken by New Horizon's Long Range Reconnaissance

 

Imager (LORRI) and was paired with four-color filter data from the Ralph/Multispectral Visible Imaging Camera. Thanks to its atmosphere, Pluto is also much colder than scientists expected,

 

according to a 2017 study.

 

 

 

 

 

Pluto's Moon Charon Is a Wild World

 

Charon is the other half of our solar system's only known planetary system. New Horizons's data suggests Charon may actually have a liquid ocean beneath its icy crust. Specifically, massive

 

extensional tectonic belts along Charon's equator indicate the moon could have, at one point, harbored a vast sea beneath the ice.

 

 

 

Thanks to Pluto, Charon Has a Bright Red Cap

 

Charon's characteristic red cap also stunned scientists. Observations have revealed this patch of red material atop the moon is the result of gases—mostly methane and other hydrocarbons—that

 

have been expelled off of Pluto and accumulated on the nearby moon.

 

 

 

 

Hydra and Nix Contain Multitudes

 

New Horizons also captured the first close-up images of Pluto's moons, Nix and Hydra. Hydra, shown here, has a highly reflective surface, leading researchers to believe it's mostly made of water

 

ice. Nix, on the other hand, has a reddish hue, which researchers believe could be the result of massive impact crater.

 

 

 

 

 

 

 

 

 

 

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[Jogs]

We have better photos of Pluto than the far side of the Moon.

Doesn't that mean something!