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I am now running my annual July fund-raising campaign to celebrate the twelfth anniversary of the establishment of Behind the Black. For many reasons, mostly political but partly ethical, I do not use Google, Facebook, Twitter. These companies practice corrupt business policies, while targeting conservative websites for censoring, facts repeatedly confirmed by news stories and by my sense that Facebook has taken action to prevent my readers from recommending Behind the Black to their friends.


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Giant wind eddies in the sands of Mars

Wind eddies on Mars
Click for full image.

Cool image time! The image to the right, cropped and reduced to post here, was photographed by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on August 5, 2020. It shows a cluster of the crescent-shaped gullies, apparently carved from desert sand by the prevailing winds.

Those prevailing winds here are from the southwest to the northeast. As the wind blows the sand to the east, it hits a more solid object, such as a mountain buried in the sand, which forces the wind and the blown sand to go around, much as water passes a boulder in river rapids. That solid object also causes an eddy to form at its face, the wind forced downward and then around and up, carving out the gullies by lifting the sand at the base of that solid object. The result are these crescent gullies, dubbed blow-outs.

The overview map helps explain why there is so much sand here, enough apparently to bury whole mountains.

Overview map

The white box near the center of the map indicates the location of this image. It is in the middle of the Medusae Fossae Formation, the largest ash deposit on Mars, about the size of India and many feet deep. Laid down in many layers over almost a billion years from 3 to 4 billion years ago, this ash field is also thought to be the source of much Mars’ dust and sand.

A survey of all nearby MRO high resolution images finds a lot of these crescent-shaped gullies, all located on the eastern slope of a large 650-mile-long north-south ridge dubbed Eumenides Dorsum and oriented in approximately the same way. My guess is that the temperature differences between the top and bottom of this ridge causes the wind to flow its slopes, thus creating these blow-outs.

Conscious Choice cover

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.


Available everywhere for $3.99 (before discount) at Amazon, Barnes & Noble, and all ebook vendors, or direct from the ebook publisher, ebookit. And if you buy it from ebookit you don't support the big tech companies and I get a bigger cut much sooner.


  • Lee Stevenson

    You don’t get as many comments on your cool images as the political posts… But I can assure you that they are very much appreciated Bob. Your eye is sharp and your analysis always thoughtful.
    This stuff is literally not published anywhere else, and your hard work is lapped up by this socialist, regardless of any difference in opinion. Thank you.

  • Chris

    Hi Bob

    Are there any theories on why MArs even has prevailing winds from the southwest or from any direction – or why there are any prevailing winds?

  • Chris: Theories exist. I think however that they are based almost always on local conditions, such as what I described in this post.

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