Pluto's methane ice caps are made from a completely different process than ice caps on Earth

NASA has published new research conducted by an international team of scientists, including some from the NASA Aims Research Center. The researchers analyzed data captured by the New Horizon spacecraft when it flew by Pluto in 2015. Researchers knew that Pluto was covered by a blanket of methane ice, creating bright deposits that were very similar to snow-capped mountains found on Earth.

The new research conducted by the international team analyzed the New Horizons data about Pluto's atmosphere and its surface. Researchers use numerical simulations of Pluto's climate to discover that its ice caps are created using an entirely different process than Earth. Tanguy Bertrand, one of the project researchers and lead author on the paper, said that it's particularly remarkable to see very similar landscapes on Earth and Pluto created by very different processes.

The scientists noted that nowhere else in the solar system has ice capped mountains like this other than Earth. On the Earth, atmospheric temperature decreases with altitude because of cooling induced by the expansion of air in upward motions. As the moist wind approaches mountains on our planet, the water vapor cools and condenses to form clouds, which turns into the snow we see on mountaintops.

On Pluto, the processes is the opposite of that on our planet. On Pluto, the atmosphere gets warmer as altitude increases because methane is more concentrated in the upper atmosphere and absorbed solar radiation. The dwarf planet's atmosphere is so thin it's unable to change surface temperatures, which remain constant. While winds travel upwards across mountains on Earth, on Pluto, winds typically travel down the mountains.

To understand what's happening on Pluto, researchers developed a 3D model of the climate at the Laboratoire de Météorologie in Paris, France, to simulate the atmosphere over time. The model showed that Pluto's atmosphere is more gaseous methane at its warmer, higher altitudes allowing the gas to saturate, condense, and freeze directly on mountain peaks without cloud formation. Methane frost doesn't happen at lower elevations because there's less gaseous methane meaning condensation can't occur.