The spacecraft New Horizons discovered impressive snow-capped mountains on Pluto in 2015, which are remarkably similar to Earth’s mountains. Never before had such a landscape been found anywhere in the solar system.
But while atmospheric temperatures on our planet decrease with altitude, due to solar radiation, they heat up on Pluto. Where is this ice coming from, then?
This question was addressed by an international team led by CNRS scientists*.
First, they determined that the “snow” on the mountains of Pluto is simply frozen methane, with traces of that gas present in the atmosphere of Pluto, much like water vapor on Earth.
Then, they used a climate model for the dwarf planet to explain how the same environment could form under such different conditions, which revealed that Pluto’s atmosphere is rich in gaseous methane due to its peculiar dynamics at high altitudes.
As a consequence, the air contains ample methane to condense only at the tops of mountains high enough to enter this enriched region.
The air is too low in methane at lower altitudes for ice to form.
This research, published in Nature Communications, can also explain why, unlike the flat Earth glaciers, which are made of water, the dense, methane glaciers found elsewhere on Pluto feature spectacular jagged ridges.
* This study was carried out by scientists from the IPSL Dynamic Meteorology Laboratory (CNRS / Sorbonne Université / École polytechnique / ENS Paris), the Grenoble Institute of Planetary Sciences and Astrophysics (CNRS / Université Grenoble Alpes), the NASA Ames Research Center and the Lowell Observatory (United States).
For more information on this study:
The ice caps of Pluto are made of methane, turning the mechanism of the planet on its head.
Earth vs. Pluto: with very different origins, snowy and frozen peaks
By Tanguy Bertrand, François Forget, Bernard Schmitt, Oliver L. Reference: “Equatorial mountains on Pluto are covered by methane frosts resulting from a unique atmospheric process”
White and William M. Grundy, Nature Communications, October 13, 2020. DOI: 10.1038/s41467-020-18845-3