Thanks to their latest images, NASA space probes are showing us the chilling beauty of Martian winters. If for many, winter is a difficult season in Quebec, these images allow us to take a little height. We found worse than the Quebec winter: a winter on Mars.
At (only) 91,000 km from Earth, Mars is our closest neighbor and shares many of our characteristics. The seasons, for example. These are longer and a little rougher than with us, on the other hand. The images were taken at the poles where, as on Earth, the conditions are the most extreme. On Mars, temperatures can drop to over -123°C at these latitudes.
Does it snow on Mars?
Yes and no. There are two types of snow on Mars: one is what we know on Earth, made of frozen water. The very thin atmosphere and sub-zero temperatures mean that the snow sublimates. That is to say, it passes directly from the solid to gaseous state, before touching the ground.
The other type of Martian snow is carbon dioxide, or dry ice, and it can land on the surface. Several meters can accumulate in flat regions near the poles.
“There are enough falls for you to snowshoe across it,” said Sylvain Piqueux, a Mars scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., in a statement released by NASA. “If you’re looking to ski, you should go to a crater or cliff side, where snow could accumulate on a sloping surface. »
So far, no orbiter or rovers have been able to see snow falling on the red planet, because the phenomenon is very difficult to observe: it only occurs at the poles, under clouds and at night.
What would Martian snowflakes look like?
On Earth, snowflakes all have a hexagonal geometry. Martian snowflakes would probably look a little different if they could be observed under a microscope.
“Because carbon dioxide ice has a symmetry of four, we know that dry ice snowflakes would be cube-shaped,” Piqueux said.
Frost, frost and ice
Jellies composed of ice and carbon dioxide also form on Mars, and they can occur farther from the poles. The Odyssey orbiter (which entered Mars orbit in 2001) saw frost forming and turning to gas in sunlight, while Viking landers spotted frost on Mars as they arrived in the 1970s.
At the end of winter, the season’s ice build-up melts and turns into gas. By sublimating itself, the ice completely redraws the landscape.