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Slushy floor of southern Martian crater?

Knobby floor of southern crater
Click for full image.

The cool image to the right, rotated, cropped, and reduced to post here, shows the northwest section of the floor of a crater in the southern cratered highlands of Mars, in a mountainous region dubbed Claritus Fossae, located south of Valles Marineris. The photo was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on May 14, 2020.

The entire crater floor appears to be covered by these strings of closely-packed knobs, reminiscent of the brain terrain found in the mid-latitude glacial regions of Mars and thought to be the result of underground ice sublimating upward.

Below is the area in the white box, in full resolution.

close-up of crater floor

To my eye this surface looks like a sheet of ice that has had hot water sprayed upon it, causing the spots where the droplets landed to melt. According to present theories, the melted spots here are instead caused when spots in the ice below the surface sublimate to a gas and pop upward, creating the depressions between the knobs. Think of the bubbles that rise in simmering tomato sauce.

Since the ice has apparently all softened, the upward popping gas does not have much problem breaking through. It is also helped by breaking through at weak points, likely the edges of multiple glacial layers (thus explaining the parallel alignments here). In a sense, we are looking a slushy ice, ready to vanish.

Why some mid-latitude glacial features look like this, while others more resemble Earth-type glaciers, remains a mystery.

Overview map

The overview map to the right provides some geographic context. This crater is found at the white cross in Claritus Fossae.

Right now Mars’ rotational tilt, its obliquity, is similar to Earth’s at 25 degrees. This is also about the mid-point of the range of this obliquity, from 11 to 60 degrees. When the tilt is high, the poles are warmer than the mid-latitudes, and the water ice migrates from the former to the latter, making the glaciers active. When the tilt is low, the mid-latitude glaciers then sublimate away, their water migrating back to the poles.

It is believed that the glaciers and the poles are generally in a steady-state today, though if there is any trend it would have the mid-latitude glaciers disappearing and the poles growing. Possibly here the debris layer that usually protects Martian ice from sublimating has been blown away, allowing the ice to begin to disappear more quickly.

Or not. I am guessing. We need a closer, more detailed look to better understand Mars’ strange geology. We are only now beginning to get a real glimpse at it.

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Conscious Choice cover

Now available in hardback and paperback as well as ebook!

 

From the press release: In this ground-breaking new history of early America, historian Robert Zimmerman not only exposes the lie behind The New York Times 1619 Project that falsely claims slavery is central to the history of the United States, he also provides profound lessons about the nature of human societies, lessons important for Americans today as well as for all future settlers on Mars and elsewhere in space.

 
Conscious Choice: The origins of slavery in America and why it matters today and for our future in outer space, is a riveting page-turning story that documents how slavery slowly became pervasive in the southern British colonies of North America, colonies founded by a people and culture that not only did not allow slavery but in every way were hostile to the practice.  
Conscious Choice does more however. In telling the tragic history of the Virginia colony and the rise of slavery there, Zimmerman lays out the proper path for creating healthy societies in places like the Moon and Mars.

 

“Zimmerman’s ground-breaking history provides every future generation the basic framework for establishing new societies on other worlds. We would be wise to heed what he says.” —Robert Zubrin, founder of founder of the Mars Society.

 

All editions are available at Amazon, Barnes & Noble, and all book vendors, with the ebook priced at $5.99 before discount. The ebook can also be purchased direct from my ebook publisher, ebookit, in which case you don't support the big tech companies and I get a bigger cut much sooner.

 

Autographed printed copies are also available at discount directly from me (hardback $24.95; paperback $14.95; Shipping cost for either: $5.00). Just email me at zimmerman @ nasw dot org.

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