NASA explores a winter wonderland on Mars – alien holiday scene with cube-shaped snow

NASA explores a winter wonderland on Mars – alien holiday scene with cube-shaped snow

NASA explores a winter wonderland on Mars – alien holiday scene with cube-shaped snow

Winter wonderland on Mars

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

When winter comes[{” attribute=””>Mars, the surface is transformed into a truly otherworldly holiday scene. Snow, ice, and frost accompany the season’s sub-zero temperatures. Some of the coldest of these occur at the planet’s poles, where it gets as low as minus 190 degrees Fahrenheit (minus 123 degrees Celsius).

Frosted Dunes in the Depths of Winter on Mars

The HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter captured these images of sand dunes covered by frost just after winter solstice. The frost here is a mixture of carbon dioxide (dry) ice and water ice and will disappear in a few months when spring arrives. Credit: NASA/JPL-Caltech/University of Arizona

Cold as it is, don’t expect snow drifts worthy of the Rocky Mountains. No region of Mars gets more than a few feet of snow, most of which falls over extremely flat areas. And the Red Planet’s elliptical orbit means it takes many more months for winter to come around: a single Mars year is around two Earth years.

Snow also falls on Mars and ice and frost form.[{” attribute=””>NASA’s spacecraft on and orbiting the Red Planet reveal the similarities to and differences from how we experience winter on Earth. Mars scientist Sylvain Piqueux of JPL explains in this video. Credit: NASA/JPL-Caltech

Still, 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’ve discovered:

Two Kinds of Snow

Martian snow comes in two varieties: water ice and carbon dioxide, or dry ice. Because Martian air is so thin and the temperatures so cold, water-ice snow sublimates, or becomes a gas, before it even touches the ground. Dry-ice snow actually does reach the ground.

“Enough falls that you could snowshoe across it,” said Sylvain Piqueux, a Mars scientist at NASA’s Jet Propulsion Laboratory in Southern California whose research includes a variety of winter phenomena. “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.”

Seasonal Changes of Polar Megadunes on Mars

HiRISE captured these “megadunes,” also called barchans. Carbon dioxide frost and ice have formed over the dunes during the winter; as this starts to sublimate during spring, the darker-colored dune sand is revealed. Credit: NASA/JPL-Caltech/University of Arizona

How We Know It Snows

Snow occurs only at the coldest extremes of Mars: at the poles, under cloud cover, and at night. Cameras on orbiting spacecraft can’t see through those clouds, and surface missions can’t survive in the extreme cold. As a result, no images of falling snow have ever been captured. But scientists know it happens, thanks to a few special science instruments.

NASA’s Mars Reconnaissance Orbiter can peer through cloud cover using its Mars Climate Sounder instrument, which detects light in wavelengths imperceptible to the human eye. That ability has allowed scientists to detect carbon dioxide snow falling to the ground. And in 2008, NASA sent the Phoenix lander 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 scientists can measure the size and shape distribution of snow particles layer by layer during a storm. The Global Precipitation Measurement mission is an international satellite project that delivers next-generation observations of rain and snow worldwide every three hours. Credit: NASA’s Goddard Space Flight Center/Ryan Fitzgibbons

Cubic Snowflakes

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

“Because carbon dioxide ice has a symmetry of four, we know that dry ice snowflakes are cubic,” Piqueux said. “Thanks to the Mars Climate Sounder, we can see that these snowflakes are smaller than the width of a human hair.”

Mars cool as ice

The HiRISE camera captured this image of the rim of a crater in the middle of winter. The crater’s southward slope, which receives less sunlight, has formed splotchy clear ice, shown in blue in this image with enhanced colors. Credits: NASA/JPL-Caltech/University of Arizona

Jack Frost is nibbling at your robber

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

Mars spring fans and polygons

HiRISE captured this springtime scene when water ice frozen in the ground had split the ground into polygons. Translucent carbon dioxide ice allows sunlight to shine through and heats gases escaping through vents, releasing fans of darker material on the surface (shown as blue in this color-enhanced image). Credits: NASA/JPL-Caltech/University of Arizona

The miraculous end of winter

Perhaps the most amazing discovery comes at the end of winter, when all the accumulated ice begins to “thaw” and sublimate into the atmosphere. As it does this, this ice takes on bizarre and beautiful shapes that scientists have recalled spiders, Dalmatian spots, fried eggsand Swiss cheese.

This “thawing” also causes geysers to erupt: translucent ice allows sunlight to heat up gas below, and that gas eventually erupts, causing fans of fabric on the surface. Scientists have actually started studying these fans as a way to learn more about them which way the Martian winds blow.

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