On Earth, the high peaks that rise into the sky and their snow glistening in the sun make the snow-capped mountains beautiful. Other planets, like Mars and Venus and even some moons, also have mountains, but they lack the cover of that iconic snow characteristic of terrestrial mountains. However, there is one notable exception discovered in 2015 by the New Horizons spacecraft. On Pluto. In sweeping across the confines of our solar system, he found snow-capped mountains.
Despite being a dwarf planet, this world on the edge of the solar system has glaciers, avalanches, a liquid ocean beneath its icy crust, a complex atmosphere, and tall mountains. Pluto’s frozen surface varies greatly, featuring regions dominated by different types of ice, from frozen methane to frozen nitrogen and even water ice.
Pluto, located more than 5.8 billion kilometers from the Sun, is an icy world in which temperatures usually drop to minus -232 degrees Celsius. Given these frigid conditions, it’s no wonder Pluto is mostly covered in ice and snow.
It was surprising enough to discover that Pluto not only has mountains – given its small size – but that Pluto’s red mountains also had snow on their peaks . However, a new study published in the journal Nature Communications exposes the significant difference between the mountains on Earth and those on Pluto. The “snow” or frost on Pluto consists of frozen methane (CH4) rather than water ice crystals and could have formed from the top down rather than from the bottom up, contrary to how layers of snow form in the earth.
Methane frost
The peaks examined by the researchers lie on the edge of the iconic heart-shaped glacier at Pluto’s equator, in a region known as Cthulhu . It is the only place other than Earth in our solar system known to have white-peaked mountains.
These mountains are about 4 km high and are made of ice water as hard as rock on Earth due to the very low temperatures of the planet. Hence it is so shocking that the icy, sparkling peaks are composed primarily of methane-rich ice. Frozen methane.
How did this methane frost form?
Pluto’s thin atmosphere is mostly nitrogen, with traces of methane and carbon monoxide. With so little methane, where does so much snow come from? Scientists determined that the dynamics of Pluto’s atmosphere concentrates methane at higher altitudes, since only on mountain tops is there enough methane to form snow (at lower altitudes there is not enough methane).
Examining the high-resolution New Horizons data, focusing on the composition of the frost at high altitudes, they found that the frost in the snow cover “is almost pure methane ice , with traces of nitrogen ice.”
Pluto, a complex world
It is a new atmospheric process that forms these Plutonian snowy mountains. The atmospheric circulation on Pluto can concentrate methane gas a few kilometers above the plains of the dwarf planet. This, in turn, can cause methane to condense as frost on mountain tops (because, interestingly, the temperature on Pluto increases with altitude). Such activity could also help explain how other methane reservoirs formed on Pluto, the authors conclude. It could also justify the formation of the methane deposits of Triton, Neptune’s moon.
Referencia: Equatorial mountains on Pluto are covered by methane frosts resulting from a unique atmospheric process. Nature Communications (2020). DOI: 10.1038/s41467-020-18845-3
