Since NASA’s New Horizons probe passed by Pluto about eight months ago, scientists have picked apart every scrap of data, discovering all sorts of new information about the dwarf planet. But even with the troves of Pluto-related finds over the last year, there is still plenty more to come as New Horizons continues to beam data back home.
This week, researchers published a set of five studies in the journal Science detailing new discoveries about Pluto’s geology and atmosphere that make it one of the strangest and most surprising objects in our solar system. Here are five new things to know about Pluto:
Pluto is geologically diverse
As far as planets go, Pluto is small, which is why it got downgraded to dwarf planet back in 2006. Pluto is about 70 percent the size of our moon, but it is geologically diverse for its size. The dwarf planet’s surface is riddled with craters, canyons, and valleys as well as layers of water ice and the more volatile frozen nitrogen, methane, and carbon monoxide, Loren Grush reports for The Verge.
Pluto’s surface is still shifting
Because nitrogen, methane, and carbon monoxide transition more easily between liquid and frozen states than water ice, parts of Pluto’s surface are constantly changing. This surface is one that could contain surreal landforms like volcanoes that spew ice and tremendous ice mountains that appear to float like icebergs on a frozen ocean, Scott K. Johnson writes for Ars Technica. Judging by some of the new data, scientists believe that other icy landforms, like the Sputnik Planum, are constantly melting and reforming due to the lack of craters seen on their surfaces.
The atmosphere is more stable than scientists once thought
According to new information gathered by New Horizons, Pluto actually has a thicker and more stable atmosphere than scientists believed. Earlier data from the probe suggested that the dwarf planet’s atmosphere was losing nitrogen rapidly, but new analysis suggests that finding was a mistake, Kenneth Chang reports for the New York Times. It now appears that Pluto’s atmosphere is only leaking nitrogen at about a hundredth the rate scientists initially believed, thanks to the atmosphere’s cold outer layers.
Pluto’s atmosphere has distinct layers
The atmosphere extends about 932 miles above Pluto’s surface and is mostly made up of a mix of nitrogen and methane. However, it also contains high levels of organic compounds like acetylene, ethylene, and ethane created by ultraviolet light interacting with the methane gas in its atmosphere. When these compounds combine, they form reddish, soot-like particles called tholins, which produce haze, Maddie Stone reports for Gizmodo. Intriguingly, these particles sort themselves into stratified layers that can clearly be seen in photos taken by New Horizons. While scientists aren’t sure exactly what causes the haze to separate into distinct layers, one theory is that they are caused by gravity waves from Pluto’s pull on the atmosphere (which are different from gravitational waves).
Pluto’s moons spin faster than they should be
Finally, there is the odd behavior of Pluto’s four smaller moons. The four tiny moons were formed about 4 billion years ago by the same ancient impact that created Pluto’s large moon, Charon. Scientists still aren’t sure exactly what the four smaller moons are made of, but they believe that they are composed of ice ripped away from Pluto’s outer surface during the event, Stone reports. What’s odd, though, is how they move through space. As depicted in a NASA visualization, Pluto’s four tiny moons spin rapidly and at odd angles as they orbit around the dwarf planet, and researchers still don’t know why. As study author Bill McKinnon tells Stone, the movements of these moons are unlike anything observed in the solar system so far, and more research needs to be done to figure out why.