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 reworked into a very otherworldly scene. Snow, ice, and frost typically accompany the season’s sub-zero temperatures. A few of 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 count on snow drifts worthy of Earth’s Rocky Mountains. As a result of Mars’ environment is so skinny, no Martian area will get various ft 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 return round. A single Mars 12 months is round two Earth years. So seasons final twice as lengthy on Mars as they do on Earth.
Nonetheless, the planet affords distinctive winter phenomena that scientists have been capable of research, with the help of NASA’s robotic Mars explorers. Beneath are just a few 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 fuel, 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. When 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, underneath cloud cowl, and at night time. 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 realize it occurs, thanks to a couple 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 possibly detect mild in wavelengths imperceptible to the human eye. That capacity 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 after they freeze, snowflakes on Earth have six sides. The identical precept applies to all water crystals. The way in which during which atoms prepare themselves determines a crystal’s form.
Within the case of carbon dioxide, molecules in dry ice at all times bond in types of 4 when frozen. In accordance with Piqueux:
As a result of carbon dioxide ice has a symmetry of 4, we all know dry-ice snowflakes could be cube-shaped. Because of the Mars Local weather Sounder, we will 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 kind frost on Mars. And each forms of frost seem way more extensively throughout the planet than snow does. The Viking landers noticed water frost after they studied Mars within the 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 exquisite 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 fuel beneath it, and that fuel finally bursts out, sending fans of dust onto the floor. Scientists have begun to check these followers as a strategy to study extra about which approach 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.
