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Curiosity presently traveling over broken sandstone from an ancient dune field

Gator-back terrain on Mars
Click for full image.

According to a new paper, scientists now think that the rough and broken cap layer of the Greenheugh pediment that Curiosity is presently traveling across was originally a dune field periodically washed by water runoff, which with time eventually hardened into sandstone.

That broken terrain, dubbed “gator-back terrain” by the Curiosity science team, is shown clearly in the image to the right, taken on March 20, 2022. From the paper’s abstract:

The Greenheugh pediment is capped by a unit of broadly uniform thickness which represents the remains of the Stimson dune field that existed <2.5 Ga (mid- to late-Hesperian). ChemCam geochemical data shows that the sands deposited at the Greenheugh capping unit were sourced from a nearby olivine-rich unit. Surface waters then cemented the windblown sand deposits, ponding at the unconformity with the underlying mudstone unit, creating concretions towards the base. Episodes of groundwater circulation did not affect the rocks at Greenheugh as much as they did at other Stimson localities with the exception of acid-sulfate alteration that occurred along the unconformity. These results suggest that the ancient Stimson dune field was a dynamic environment, incorporating grains from the surrounding geological units on Mt Sharp. Furthermore, liquid water was stable at the surface in the Hesperian and was available for multiple diagenetic events along bedrock weaknesses.

In other words, material from Mount Sharp formed the dune fields, all of which were reshaped by groundwater circulation, with the dunes higher on the mountain seeing less groundwater.

The biggest uncertainty of these findings is explaining how surface liquid water could exist on Mars. Scientists have yet to develop an accepted model that would allow it. Another possibility would be the recent data that suggests Gale Crater was filled with glaciers. If so, scientists would need to figure out how the interaction of a Martian glacier might have geologically changed those dunes in a manner similar to groundwater.

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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