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The knobby floor of a Martian crater

The knobby floor of a Martian crater

Cool image time! The picture to the right, rotated, cropped, reduced, and enhanced to post here, was taken on July 20, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a small portion of the knobby floor of a 70-mile-wide ancient and eroded unnamed crater in the southern cratered highlands of Mars.

Why knobby? Usually such terrain on Mars signifies an very ancient and well eroded region of chaos terrain, its knobs the leftover worn remains of ancient mesas cut by eons of glacier flow.

If this is so, the location as shown in the overview map below suggests if there were ever any glaciers — or any near surface ice — at this location, it had to be a very long time ago.

Overview map

The white cross marks the location of this crater, on the northern edge of the southern cratered highlands and deep inside the dry equatorial regions of Mars. There is no near surface ice here, with the nearest detected by data and orbital imagery many hundreds of miles away, all north or south of the 30 degree latitude lines on the map.

What makes the knobs in this particular large crater even more puzzling is that most of the comparably sized nearby craters have smooth floors, with no such knobs. It could be their floors have been flooded with lava at some time, thus covering the more ancient knobs, but if so, why was there no flood lava in this crater?

Ah, the mysteries of Mars. The cratered highlands of Mars I suspect will always be somewhat of an enigma. Most of its many craters are unnamed, even though many are large and distinct. Much of it is is also in the dry parts of Mars, with no ice. And because of the high altitude the atmosphere is thinner. All in all, a less appetizing location for future colonists.

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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