© NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute. The polar cap of « Sputnik Planum », in false colors, is surrounded by mountains which have been eroded and shaped by the glacial activity. The dark areas are covered by organic materials produced by the photolysis of methane by solar ultraviolet light.
What is the origin of the large heart-shaped nitrogen glacier revealed in 2015 on Pluto by the New Horizons spacecraft? Two researchers from the Laboratoire de météorologie dynamique (CNRS/École polytechnique/UPMC/ENS Paris)
1 show that Pluto's peculiar insolation and atmosphere favor nitrogen condensation near the equator, in the lower altitude regions, leading to an accumulation of ice at the bottom of Sputnik Planum, a vast topographic basin. Through their simulations, they also explain the surface distribution and atmospheric abundance of other types of volatiles observed on Pluto. These results are published in Nature on September 19, 2016. Pluto is a paradise for glaciologists. Among the types of ice covering its surface, nitrogen is the most volatile: when it sublimes
2 (at -235 ° C), it forms a thin atmosphere in equilibrium with the ice reservoir at the surface. One of the most unexpected observations from New Horizons , which flew by Pluto in July 2015, showed that this reservoir of solid nitrogen is extremely massive, and mostly contained in "Sputnik Planum", a topographic basin located within the tropics of Pluto. Methane frost also appears all over the northern hemisphere
3, except at the equator, while carbon monoxide ice in smaller amounts was only detected in Sputnik Planum.
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