NASA explores a winter wonderland on Mars

This image, taken by NASA’s Mars Reconnaissance Orbiter on July 22, 2022, shows sand dunes moving across the land. Winter frost covers the colder north-facing half of each dune. Credit: NASA/JPL-Caltech/University of Arizona

Cube-shaped snow, icy landscapes and frost are all part of the Red Planet’s coldest season.

When winter arrives on Mars, the surface transforms into a truly otherworldly holiday scene. The sub-zero temperatures of the season are accompanied by snow, ice and frost. Some of the coldest of these occur at the planet’s poles, where it drops as low as minus 190 degrees Fahrenheit (minus 123 degrees Celsius).

No matter how cold the weather, don’t expect the snowfall befitting the Rocky Mountains. No area of ​​Mars receives more than a few meters of snow, most of which falls on extremely flat areas. And the Red Planet’s elliptical orbit means it will take more months for winter to arrive: A single Martian year is roughly two Earth years.

Yet the planet offers unique winter phenomena that scientists have been able to study thanks to NASA’s robotic Mars explorers. Here are a few of the things they discovered:

NASA explores a winter wonderland on Mars

HiRISE has taken over these “mega dunes”, also called barchans. During the winter, carbon dioxide frost and ice formed on the dunes; This results in darker dune sand as it begins to sublimate in the spring. Credit: NASA/JPL-Caltech/University of Arizona

two kinds of snow

Martian snow is of two types: water ice and carbon dioxide or dry ice. Because Martian air is so thin and temperatures are so cold, water-ice snow sublimes or turns into a gas before it even touches the ground. Dry ice snow actually reaches the ground.

“There’s as much fall as you can get through with snowshoes,” said Sylvain Piqueux, a Mars scientist at NASA’s Jet Propulsion Laboratory in Southern California who has research involving various winter phenomena. “If you still want to ski, you’ll need to go to a crater or cliff edge where snow can accumulate on a sloping surface.”






It also snows on Mars, forming ice and frost. NASA’s spacecraft on and in orbit on the Red Planet reveals the similarities and differences in how we experience winter on Earth. Mars scientist Sylvain Piqueux of JPL explains it in this video. Credit: NASA/JPL-Caltech

How do we know when it’s snowing?

Snow forms only at the coldest extremes of Mars: at the poles, under the clouds, and at night. Cameras on orbiting spacecraft cannot see through these clouds, and surface missions cannot survive the extreme cold. As a result, no footage of falling snow was captured. But scientists know it’s happening, thanks to a few specialized science tools.

NASA’s Mars Reconnaissance Orbiter can peer through cloud cover using the Mars Climate Sounder instrument, which detects light in wavelengths invisible to the human eye. This ability allowed the scientists to detect carbon dioxide snow falling to the ground. And in 2008, NASA sent the Phoenix lander to within 1,000 miles (about 1,600 kilometers) of Mars’ north pole, where it used a laser instrument to detect water-ice snow falling to the surface.

NASA explores a winter wonderland on Mars

The HiRISE camera captured this image of the rim of a crater in mid-winter. The south-facing slope of the crater, which receives less sunlight, has produced patchy, bright frost, seen in blue in this enhanced color image. Credit: NASA/JPL-Caltech/University of Arizona

cubic snowflakes

Snowflakes on Earth have six edges because water molecules bond together when they freeze. The same principle applies to all crystals: The way atoms arrange themselves determines the shape of a crystal. In the case of carbon dioxide, the molecules in dry ice always bind in a quadruple form when frozen.

“Since the symmetry of carbon dioxide ice is four, we know that dry ice snowflakes will be cube-shaped,” Piqueux said. Said. “Thanks to the Mars Climate Siren, we can tell that these snowflakes will be smaller than the width of a human hair.”

Jack Frost pinches your traveler

Water and carbon dioxide can each create frost on Mars, and both types of frost are much more common on the planet than snow. Viking landers saw water freeze when they surveyed Mars in the 1970s, while NASA’s Odyssey orbiter observed ice formation and sublimation in the morning sun.

NASA explores a winter wonderland on Mars

HiRISE captured this spring scene where water ice frozen in the soil divides the ground into polygons. The translucent carbon dioxide ice allows sunlight to shine through and heats the gases escaping through the vents, leaving darker material fans on the surface (shown in blue in this enhanced color image). Credit: NASA/JPL-Caltech/University of Arizona

great end of winter

Perhaps the most spectacular discovery comes at the end of winter, when all the accumulating ice begins to “melt” and sublimate into the atmosphere. In doing so, this ice takes on strange and beautiful shapes that remind scientists of spiders, Dalmatian spots, scrambled eggs and Swiss cheese.

This “thaw” also causes geysers to explode: The translucent ice allows sunlight to heat the gas underneath, and this gas eventually explodes, sending dust fans to the surface. Scientists began studying these fans as a way to learn more about which direction Martian winds are blowing.

Quotation: NASA explores a winter wonderland on Mars (2022, December 23), retrieved December 23, 2022 from https://phys.org/news/2022-12-nasa-explores-winter-wonderland-mars.html .

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