These stunning NASA visuals shows a wonderous winter on Mars

NASA is making the case for a "winter wonderland" on Mars
Ayesha Gulzar
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NASA’s Mars Reconnaissance Orbiter captured this image of sand dunes covered by frost just after winter solstice

Though dreaming of a white Christmas may not immediately conjure up images of the extraterrestrial landscapes found in the coldest regions of Mars, NASA is presenting the idea of a "winter wonderland" on the Red Planet. Its numerous missions over the past few decades have uncovered strange icy features on Mars and how much the Red planet sometimes resembles Earth.

In winter, the temperatures on Mars drop to sub-zero levels. Some of the coldest temperatures occur at the poles, where it can get as cold as -190 degrees Fahrenheit (-123 degrees Celsius). However, no region of Mars receives more than a few feet of snow, most of which falls over extremely flat areas.

"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."

How do we know it snows on Mars?

It is not possible to observe snowfall directly on the planet due to the challenges of operating in an extremely cold and thin atmosphere. But thanks to specialized instruments, scientists have confirmed snowfall on the Red planet.

NASA's Mars Reconnaissance Orbiter can peer through cloud cover using its Mars Climate Sounder instrument. It can detect light in wavelengths not visible to the human eye, allowing it to see through cloud cover and observe the surface of Mars. With this instrument, scientists have been able to detect carbon dioxide snowfall on the planet.

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Also, in 2008, NASA sent the Phoenix lander within 1,000 miles (about 1,600 kilometers) of Mars' north pole, using a laser instrument to detect water-ice snow falling to the surface.

These stunning NASA visuals shows a wonderous winter on Mars

Two types of snow

There are two main types of snow on Mars: water ice snow and carbon dioxide (CO2) ice snow or dry ice. Due to the thin Martian air and freezing temperature, the dry ice sublimates rather than melting, as water ice does, thus creating bizarre landscapes as it transforms from a solid to a gas.

Snowflakes with four sides

On Earth, snowflakes contain six sides or points, owing to how they form. The molecules in ice crystals join in a hexagonal structure, an arrangement that allows water molecules to form together most efficiently. This principle applies to all crystals, as the arrangement of atoms determines the shape of the crystal. In the case of carbon dioxide, or "dry ice," the molecules always bond in forms of four when frozen.

"Because carbon dioxide ice has a symmetry of four, we know dry-ice snowflakes would be cube-shaped," Piqueux said. "Thanks to the Mars Climate Sounder, we can tell these snowflakes would be smaller than the width of a human hair."

These stunning NASA visuals shows a wonderous winter on Mars

A wondrous end of winter on the Red planet

One of the most exciting discoveries about winter on Mars occurs as the winter season comes to an end and the accumulated ice begins to "thaw." It transitions directly from a solid to a gas in a process called sublimation. During this process, the ice takes on strange and beautiful shapes that have reminded scientists of spiders, Dalmatian spots, fried eggs, and Swiss cheese.