Martian hardened dunes untouched by dust devils
Click for original image.
Cool image time! The picture to the right, cropped to post here, was taken on September 26, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).
I picked this image out of the MRO archive because of the many dust devil tracts that cut across the entire image, traveling in all directions with no apparent pattern. I also picked it because those tracks also cut across the many parallel small ridges that appear to be ancient ripple dunes that have since hardened into rock. What makes this landscape puzzling is how those dust devil tracks leave no evidence on those ridges. It is as if the ancient ripple dunes were laid down after the very recent dust devil tracks, even though that is chronologically entirely backwards.
Apparently, the dust devil tracks form because the devil only disturbs the dust that coats the flat low ground between the ridges. The ridges themselves are hard, and thus the devils, produced in Mars’ extremely thin atmosphere, can leave no mark.
The white dot on overview map to the right marks the location, on the western edge of the large impact basin dubbed Argyre Basin. Argyre, about a thousand miles across with a depth of about 17,000 feet, is one of three such impact basins on Mars — the other two being Hellas and Utopia basins — all thought to be caused during the Late Heavy Bombardment about four billion years ago, when the planets of the solar system were first forming.
The location is also just outside a region where orbital data has found a lot of evidence of glacial material. This location is at 49 degrees south latitude, well inside the mid-latitudes where glacial evidence is so pervasive, but here there appears to be little near surface ice, possible because of its low elevation inside Argyre. Instead of ice, this place sits inside a large 30-mile-wide dust bowl. No wonder there are a lot of dust devil tracks here.
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 print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. 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 original image.
Cool image time! The picture to the right, cropped to post here, was taken on September 26, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).
I picked this image out of the MRO archive because of the many dust devil tracts that cut across the entire image, traveling in all directions with no apparent pattern. I also picked it because those tracks also cut across the many parallel small ridges that appear to be ancient ripple dunes that have since hardened into rock. What makes this landscape puzzling is how those dust devil tracks leave no evidence on those ridges. It is as if the ancient ripple dunes were laid down after the very recent dust devil tracks, even though that is chronologically entirely backwards.
Apparently, the dust devil tracks form because the devil only disturbs the dust that coats the flat low ground between the ridges. The ridges themselves are hard, and thus the devils, produced in Mars’ extremely thin atmosphere, can leave no mark.
The white dot on overview map to the right marks the location, on the western edge of the large impact basin dubbed Argyre Basin. Argyre, about a thousand miles across with a depth of about 17,000 feet, is one of three such impact basins on Mars — the other two being Hellas and Utopia basins — all thought to be caused during the Late Heavy Bombardment about four billion years ago, when the planets of the solar system were first forming.
The location is also just outside a region where orbital data has found a lot of evidence of glacial material. This location is at 49 degrees south latitude, well inside the mid-latitudes where glacial evidence is so pervasive, but here there appears to be little near surface ice, possible because of its low elevation inside Argyre. Instead of ice, this place sits inside a large 30-mile-wide dust bowl. No wonder there are a lot of dust devil tracks here.
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 print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. 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