Pluto is weirder and more complex than we imagined. It has a large basin with exotic ices. It has floating mountains. And earlier this year, planetary scientists discovered blades of ice as tall as skyscrapers.
In a study published in Icarus, researchers propose how these incredible structures might have formed. The blades occur at Pluto's highest altitudes, near its equator, and probably result from interactions between ice deposits and ice evaporation over millions of years.
According to the team, methane in the atmosphere freezes and crystalizes before falling to the ground and forming deposits. As a result of climate change, the frozen methane sublimates, creating incredible shapes.
“When we realized that bladed terrain consists of tall deposits of methane ice, we asked ourselves why it forms all of these ridges, as opposed to just being big blobs of ice on the ground,” said lead author Jeffrey Moore, in a statement. “It turns out that Pluto undergoes climate variation and sometimes, when Pluto is a little warmer, the methane ice begins to basically ‘evaporate’ away.”
The shapes aren't unfamiliar to scientists. Similar ice blades are found in the Chilean Andes. They are called penitentes as they reminded their discoverers of a procession of people doing penance. While similar in shape, the earthly penitentes are made of water ice and are at most 5 meters (16 feet) tall.
The research has consequences for Pluto's entire geography. NASA's New Horizons spacecraft performed a flyby observation of the dwarf planet, providing high-resolution analysis of one of its hemispheres. The blades tell us that methane ice is abundant at high altitudes, helping to improve maps of Pluto. If the composition map says there’s a lot of methane in a certain location, there’s a good chance that it’s quite high above the surface.
It’s been slightly less than a year since the full data set from New Horizons was downloaded and researchers are still working on getting everything they can from it. The NASA spacecraft is currently flying towards its next target, a Kuiper belt object called MU69. It will arrive January 1, 2019.