It is winter for people in the north. We associate the festive season with snow, rain, and cold weather. It's the same thing for Mars. It is snowing in its northern hemisphere right now. It can get as low as -123 C (-190 F) in the polar regions, as well as ice, snow, frost, and the expansion of the polar ice caps, which are composed of both water ice and frozen carbon dioxide.
Seasonal change on Mars results in some very interesting phenomena. Thanks to the many robotic explorers NASA and other space agencies have sent to Mars in the past fifty years, scientists have been able to get a close up look at these phenomena The landers that studied the planet in the 70s and the rovers that explored the surface today are included.
There are two types of snow on Mars, water ice and dry ice, and it only happens at the poles. Water and carbon dioxide don't freeze because Mars' atmosphere is so thin and its temperatures are so extreme. Dry ice snowflakes have four sides instead of the six sides we're used to.
The shape of a crystal is dependent on how atoms arrange themselves. The CO2 molecule bonds in groups of four. On Mars, snow falls from the clouds to the surface. Since most satellites can't see through the clouds, no images of falling snow have ever been taken. Scientists know that Mars gets snow thanks to a few dedicated instruments.
The Mars Climate Sounder (MCS) aboard the MRO is used to observe the temperature, humidity, and dust of the Martian atmosphere. Science teams can peer through the cloud cover to see CO 2 snow falling. In a recent interview with NASA's Mars News Report, Sylvain Piqueux, a planetary research scientist at NASA's Jet Propulsion Laboratory, explained the details of the snow on Mars. He explained it that way.
“Enough falls that you could snowshoe across it. If you were looking for skiing, though, you’d have to go into a crater or cliffside, where snow could build up on a sloped surface. Because carbon dioxide ice has a symmetry of four, we know dry-ice snowflakes would be cube-shaped. Thanks to the Mars Climate Sounder, we can tell these snowflakes would be smaller than the width of a human hair.”
The Phoenix mission landed close to the north pole of Mars. The Canadian Space Agency provided a laser-based atmospheric sensor for the landers to use to detect water ice snow. Water frost was detected at the landing sites by the Viking landers, and NASA observed frost forming and sublimating at sunrise.
The most recognizable surface features on Mars occur when the CO 2 ice sublimates. The shapes that scientists have dubbed "spiders, Dalmatian spots, fried eggs, and Swiss cheese" are included. geysers erupt as sunlight passes through translucent ice, heating the gas pockets beneath it. This causes eruptions that send dust onto the surface, creating a feature known as "Spring Fans" that scientists are studying to learn more about the direction the winds are blowing.
When it comes time to send crewed missions to Mars, all of this data will be crucial.
“[T]he Pheonix lander, the NASA mission that arrived on Mars in 2008, observed beautiful frost landscapes that formed around it. The Pheonix lander was also able to scratch the surface and, for the first time, see this water ice just below the ground. This is the kind of water ice that astronauts could potentially use in the future when we go there.”
Thanks to many generations of robotic missions, we are able to see many fascinating things on Mars. Soon astronauts will be able to see Mars and its climate firsthand, and their research will fuel discoveries for generations to come.
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