Originally published by NASA on December 22, 2022. Edits by EarthSky.
Winter wonderland on Mars
When winter comes to 1 hemisphere or the opposite of Mars, the floor could also be remodeled into a very otherworldly scene. Snow, ice, and frost typically accompany the season’s sub-zero temperatures. Among the coldest of those happen on the planet’s poles, the place it will get as little as minus 190 levels Fahrenheit (minus 123 levels Celsius).
Chilly as Mars is, don’t anticipate snow drifts worthy of Earth’s Rocky Mountains. As a result of Mars’ environment is so skinny, no Martian area will get quite a lot of toes of snow, most of which falls over extraordinarily flat areas. And the 687-day orbit of Mars means it takes many extra earthly months for winter to come back round. A single Mars yr is round two Earth years. So seasons final twice as lengthy on Mars as they do on Earth.
Nonetheless, the planet provides distinctive winter phenomena that scientists have been in a position to examine, with assistance from NASA’s robotic Mars explorers. Under are a couple of of the issues they’ve found.
Two sorts of snow
Martian snow is available in two varieties: water ice and carbon dioxide, or dry ice. As a result of Martian air is so skinny and the temperatures are so chilly, water-ice snow sublimates, or turns into a gasoline, earlier than it even touches the bottom. However dry-ice snow does attain the bottom.
Sylvain Piqueux is a Mars scientist at NASA’s Jet Propulsion Laboratory in Southern California whose analysis consists of quite a lot of winter phenomena. He mentioned:
Sufficient falls that you possibly can snowshoe throughout it. In the event you have been in search of snowboarding, although, you’d have to enter a crater or cliffside, the place snow may construct up on a sloped floor.
How we all know it snows
Snow happens solely on the coldest extremes of Mars: on the poles, beneath cloud cowl, and at evening. Cameras on orbiting spacecraft can’t see via these clouds, and floor missions can’t survive within the excessive chilly. In consequence, no pictures of snow falling on Mars have ever been captured. However scientists comprehend it occurs, thanks to some particular science devices.
NASA’s Mars Reconnaissance Orbiter can peer via cloud cowl utilizing its Mars Climate Sounder instrument. That’s as a result of it could detect gentle in wavelengths imperceptible to the human eye. That means has allowed scientists to detect carbon dioxide snow falling to the bottom.
And, in 2008, NASA despatched the Phoenix lander inside 1,000 miles (1,600 km) of Mars’ north pole, the place it used a laser instrument to detect water-ice snow falling to the floor.
Cubic snowflakes
Due to how water molecules bond collectively once they freeze, snowflakes on Earth have six sides. The identical precept applies to all water crystals. The way in which by which atoms organize themselves determines a crystal’s form.
Within the case of carbon dioxide, molecules in dry ice all the time bond in types of 4 when frozen. In keeping with Piqueux:
As a result of carbon dioxide ice has a symmetry of 4, we all know dry-ice snowflakes could be cube-shaped. Due to the Mars Local weather Sounder, we are able to inform these snowflakes could be smaller than the width of a human hair.
Jack Frost nipping at your rover
Water and carbon dioxide can every type frost on Mars. And each kinds of frost seem way more broadly throughout the planet than snow does. The Viking landers noticed water frost once they studied Mars within the Nineteen Seventies. And NASA’s Odyssey orbiter – which arrived at Mars in late 2001 – noticed frost forming and sublimating away within the morning sun.
When the winter wonderland on Mars ends
Maybe essentially the most fabulous discovery comes on the finish of winter, when all of the ice that constructed up begins to thaw and sublimate into the environment. Because it does so, this ice takes on weird and delightful shapes which have reminded scientists of spiders, Dalmatian spots, fried eggs, and Swiss cheese.
This thawing additionally causes geysers to erupt. When translucent ice permits daylight to warmth up gasoline beneath it, and that gasoline ultimately bursts out, sending fans of dust onto the floor. Scientists have begun to review these followers as a option to study extra about which means Martian winds are blowing.
Backside line: NASA’s HiRISE digicam captured fascinating pictures of the winter wonderland on Mars. When Mars thaws within the spring, the ice takes on new and weird shapes even leading to erupting geysers.
