Melting Ice on Mars?

These Mars Reconnaissance Orbiter images show in increasing magnification a puzzling feature in the southeast part of a ice mound in Louth Crater on Mars. Located at 70 degrees north latitude, this is the farthest south that scientists have found permanent water ice. The close-up image suggests melting ice with the draining water running down hill to the south, though on Mars the low air pressure would cause any liquid water to evaporate instantly. Key quote:

These may be the crests of partially defrosted dark sand dunes or perhaps some other feature that we do not understand. This is the only area on Louth where these enigmatic ridges are found.

wide view of crator mound

Middle view of ice mound

Closeup of ice mound

Picture of the day from Mars

Sand dunes on Mars, from the HiRise camera on Mars Reconnaissance Orbiter:

Dunes on Mars

Fun quote:

These dunes are “barchan” dunes, which are also commonly found on Earth. Barchan dunes are generally crescent-shaped, with their “horns” oriented in the downwind direction. They have a steep slip face (the downwind side of the dune). Barchan dunes form by winds that blow mostly in one direction and thus are good indicators of the dominant wind direction. In this case, the strongest winds blow approximately north to south.

Exploring Mars from Earth

Want to poke around on Mars? Since it might be a while before you can actually go there, I suggest you instead make frequent visits to the images page for the HiRise camera on Mars Reconnaissance Orbiter. The pictures that appear here are routinely breath-taking. Below is a cropped image showing the flat top of a mesa in Coprates Chasma. The full image shows detailed layers down the side of the mesa as well as rippled dunes on the mesa top. Everything is remarkably reminescent of something you’d see if you visited the Grand Canyon. Only on Mars, this grand canyon is many times larger and deeper.

Mesa top on Mars

Boulder tracks on Mars

Here’s a nice picture from the HiRISE camera on Mars Reconnaissance Orbiter, released July 7, showing the boulder tracks left by rocks bouncing down the escarpment of Kasei Valles in the low gravity of Mars. Fun quote:

Some of these blocks traveled downhill several hundred meters (yards) as they rolled and bounced, leaving behind a trail of indentations or poke marks in the surface’s fine-grained, light-toned soils. The raised borders in some of these poke marks indicate they are relatively recent features, unaffected by wind erosion, or that this soil has cohesive properties, such as if it was cemented.

Boulder tracks on Mars

Avalanches on Mars

Saturday’s weekly dump of publications from the American Geophysical Union also included a paper that showed visual proof of avalanches on Mars! In this case, the location is Russell Crater, “a large crater in the southern hemisphere that exposes a large dune field in its center.” The avalanches occur because a frost layer made up of dry ice and a little bit of frozen water builds up on the crest of the dunes. When that frost melts, dark streaks about three to six feet wide and about 150 feet long appear, flowing downhill. The scientists believe these are avalanches made up of “a mixing of sand, dust, and unstable CO2 gas.”

wide shot of before and after
Before and after shots of the dark streaks flowing down the dune.

close-up, before and after
Close-ups of the streaks, before and after.

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