Giant wind eddies in the sands of 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.
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.
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
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.
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.
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
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.
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.