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Martian dunes with frost and a sublimating dry ice mantle

Martian dunes surrounded by frost
Click for original image.

Cool image time! The picture to the right, cropped to post here, was taken on March 16, 2024 by the high resolution camera of Mars Reconnaissance Orbiter (MRO). It was released today as a captioned picture from MRO’s camera team. As noted in the caption, written by the camera’s principal investigator Alfred McEwen:

This image shows a field a sand dunes in the Martian springtime while the seasonal carbon dioxide frost is sublimating into the air. This sublimation process is not at all uniform, instead creating a pattern of dark spots.

In addition, the inter-dune areas are also striking, with bright frost persisting in the troughs of polygons. Our enhanced-color cutout is centered on a brownish-colored inter-dune area.

Each winter the carbon dioxide in the Martian atmosphere falls as snow, mantling the surface in the latitudes above 60 degrees with a clear coat of dry ice. When spring arrives the sunlight passes through the mantle to heat the ground below, which in turn causes the base of the dry ice mantle to sublimate into gas. When the pressure builds enough, the gas breaks through the mantle at its weak points, spewing out and bringing with it dust from below, which stains the mantle with the dark spots.

Overview map

The black dot in the overview map’s inset to the right marks the location, to the southeast of Argyre Basin. This dune field formed at the base of the north rim of an 35-mile-wide unnamed crater, located in the southern cratered highlands at 61 degrees south latitude.

If you look at the full image instead of the smaller color-enhanced section above, you can see that this section of brown frosted dunes is nestled in an alcove of a field of much larger dunes that gathered at the crater’s interior slope. On these larger dunes the dark splotches are more evident because the frost in the low points is more pronounced.

Most of the rest of the crater’s floor appears covered with a smooth surface impregnated by near surface ice and cross-crossed with dust devil tracks. It also appears that this glacial material has flowed either in or out of the crater through the gap in its southern rim.

Genesis cover

On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.

The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.

"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News

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