A Martian cliff of ash, flushed by wind
Click for original image.
Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on December 27, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Described merely as an “exposed scarp” by the science team, this cliff edge is actually much more.
First some basic details. The elevation drop from the plateau down to the base of this cliff is about a thousand feet. The material that forms this plateau, scarp, and its base is all volcanic ash. The thicker sections of ash has caused its lower levels to compress, harden into a kind of sandstone. Near the surface however it is more friable, and like sandstone can break apart somewhat more easily.
The prevailing winds at this site are generally blowing to the south, but beginning to turn to the east, which explains the northwest to southeast orientation of the features.
The best analogy I can come up with to explain the erosion of this scarp is as follows: Imagine a deposit of dry mud a few inches thick on pavement. Take a leaf blower and blow at it hard, always in one direction. Eventually the outer edge will break up and blow away, leaving a sharp edge, that will also retreat with time as the wind continues to blow.
Here the winds are eroding that cliff, causing periodic avalanches which dissolve into sand that then blows away, leaving no debris pile at the base of the cliff. The ridges indicate harder material, that breaks away last, which is why there are some ridgelines extending outward from the scarp in line with these ridges. At the same time, these ridges of harder ash still break up with time, as some are cut off suddenly at the cliff edge.
The white dot on the southern border of the Medusae Fossae Formation on the overview map to the right marks the location. Medusae is the largest ash deposit on Mars, exceeding the size of India and thought to be the source of most of the dust seen everywhere on Mars. The overview map gives us a sense of the scale of this ash deposit, the edge of which is shown in the picture above. As shown by the inset, the plateau above the scarp is actually a slope, rising another 2,000 feet to the north beyond the edge of this picture by about eighteen miles, until it reaches the top of a much larger plateau, dubbed Lucas Planum. Lucas, made up entirely of many thick layers of volcanic ash, extends further north by another 400-plus miles, and is about 500 miles wide.
There is a lot of ancient ash on Mars, suggesting a lot of past volcanic activity. That activity mostly ended a half to a billion years ago. Since then, that ash has hardened, then dissolved into dust and sand and spread across Mars, making it the dusty red planet we are only now beginning to learn something about.
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 original image.
Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on December 27, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Described merely as an “exposed scarp” by the science team, this cliff edge is actually much more.
First some basic details. The elevation drop from the plateau down to the base of this cliff is about a thousand feet. The material that forms this plateau, scarp, and its base is all volcanic ash. The thicker sections of ash has caused its lower levels to compress, harden into a kind of sandstone. Near the surface however it is more friable, and like sandstone can break apart somewhat more easily.
The prevailing winds at this site are generally blowing to the south, but beginning to turn to the east, which explains the northwest to southeast orientation of the features.
The best analogy I can come up with to explain the erosion of this scarp is as follows: Imagine a deposit of dry mud a few inches thick on pavement. Take a leaf blower and blow at it hard, always in one direction. Eventually the outer edge will break up and blow away, leaving a sharp edge, that will also retreat with time as the wind continues to blow.
Here the winds are eroding that cliff, causing periodic avalanches which dissolve into sand that then blows away, leaving no debris pile at the base of the cliff. The ridges indicate harder material, that breaks away last, which is why there are some ridgelines extending outward from the scarp in line with these ridges. At the same time, these ridges of harder ash still break up with time, as some are cut off suddenly at the cliff edge.
The white dot on the southern border of the Medusae Fossae Formation on the overview map to the right marks the location. Medusae is the largest ash deposit on Mars, exceeding the size of India and thought to be the source of most of the dust seen everywhere on Mars. The overview map gives us a sense of the scale of this ash deposit, the edge of which is shown in the picture above. As shown by the inset, the plateau above the scarp is actually a slope, rising another 2,000 feet to the north beyond the edge of this picture by about eighteen miles, until it reaches the top of a much larger plateau, dubbed Lucas Planum. Lucas, made up entirely of many thick layers of volcanic ash, extends further north by another 400-plus miles, and is about 500 miles wide.
There is a lot of ancient ash on Mars, suggesting a lot of past volcanic activity. That activity mostly ended a half to a billion years ago. Since then, that ash has hardened, then dissolved into dust and sand and spread across Mars, making it the dusty red planet we are only now beginning to learn something about.
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
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