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Sublimating scallops on Mars

Giant scallop on Mars
Click for full image.

Today’s cool image, shown in a rotated, cropped, and reduced version to the right, gives us a close-up look at one of the giant scallops found in the high mid-latitudes of the northern lowland plains of Mars, specifically in Utopia Basin north of the landing sites of both Perseverance and Zhurong. In fact, this particular image is only a few miles north of one of my previous cool images, Giant scallops on Mars, posted in December 2019.

The image was taken on February 3, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). While such scallops are not unusual in the mid-latitudes, their formation process is not well understood. As I noted in the 2019 post, ” scientists believe [pdf] the formation process is related to the sublimation of underground ice.”

According to [one hypothesis] scallop formation should be ongoing at the present time. Sublimation of interstitial ice could induce a collapse of material, initially as a small pit, then growing [away from the equator] because of greater solar heating on [that] side. Nearby scallops would coalesce together as can be seen to have occurred.

This hypothesis is not proven, and today’s cool image raises questions about it. Though the bright material at its center suggests exposed ice, supporting the idea that sublimation of ice near the surface created the scallop, the scallop scarps seem more extended and distinct to the south, not the north as this hypothesis proposes. Sunlight should hit the northern scarps more, which suggests they should retreat more instead of the southern scarp.

The overview map below provides the context.

Overview map

The two white boxes adjacent to each other near the center top show the locations of today’s image as well as the December 2019 image, no more than a few miles apart. At this latitude, 46 degrees north, a lot of evidence of near-surface ice has been found. As you move to lower latitudes that evidence fades until there is no evidence south of 30 degrees latitude.

Zhurong sits at about 25 degrees north latitude. If its ground-penetrating radar picks up any evidence of underground ice, it will have made a significant discovery, suggesting that future Martian settlers will find ice that can be mined for water and energy almost anywhere on the planet’s surface. You will simply have to dig deeper the closer to the equator you get.

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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