When New Horizons drifted past Pluto in July 2015, it gave us our first glimpse of the icy little world larger than a few pixels. The historic flyby revealed a particularly spectacular heart-shaped region on Pluto’s surface. Pluto’s heart is actually a big glacier named Sputnik Planitia, and it’s full of weird and wonderful features.
Perhaps one of the most striking features is a collection of dunes on the glacier’s eastern edge. While many places in the solar system have dunes, all of these places have an atmosphere, while Pluto has almost none. Dunes on Earth form thanks to winds, but on Pluto the air is only 0.001 percent as thick as on Earth—much too thin to sculpt dunes on its own.
So how did those dunes get there? An international group of scientists has developed a possible answer pointing to frozen nitrogen and methane.
In Pluto’s thin atmosphere, solid nitrogen sitting on mountain peaks can spontaneously evaporate, and this evaporating nitrogen can launch small particles of methane into the air. The methane particles are about the size of grains of sand, and they are light enough to be launched to high altitudes in Pluto’s low gravity and atmospheric pressure.
Once methane particles are in the air, the wispy atmosphere carries them from the mountaintops over the glacial plains, where they fall to the ground. On impact, they kick up yet more particles, which fly into the air and then fall, repeating the cycle potentially dozens of times. Over thousands of years, this creates the kind of dunes imaged by New Horizons.
What’s more, this analysis suggests that these dunes haven’t always been a part of Pluto. The research shows that the dunes are probably only about 500,000 years old at most, and are likely considerably younger. Even a cold, distant world like Pluto is constantly changing.