Exploring the cratered southern highlands of Mars, part 4
Click for full image.
Today is the last part in our four part exploration of the cratered southern highlands of Mars, begun last week. (For the early parts, go here-Part #1, here-Part #2, and here-Part #3.) Though there is no need, new readers should read the first three parts first, in order to get the larger perspective of this final post.
The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on December 20, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the eastern main gully descending down into a pit that sits in the north center of 52-mile-wide Asimov Crater, as shown in the inset on the overview map above. (For an MRO high resolution of the western gullies into this pit, see this January 2019 cool image post.)
Like Rabe Crater (also shown on the overview map) as well as all the craters around it as well as many near Asimov, the interior floor of Asimov crater is eroding away. Unlike those other craters highlighted in the previous parts of this series, today’s image shows the likely glacial ice nature of that erosion much more clearly. Note the parallel cracks cutting across the slope, all of which suggest that as the gully erodes the ice on its slope is also sagging downward, forming cracks as sections separate under the pressure of gravity. Since this region of the southern cratered highlands is all inside the 30 to 60 degree latitude band where scientists have generally found ample evidence of buried glaciers or ice, such glacier-like features should not surprise us.
Overall, our short survey of the southern cratered highlands suggests that the glacial material and ice found in the southern mid-latitudes affects the Martian surface differently than in the northern lowland plains. In the north the craters and the surrounding terrain often appear blobby, as if the ice is close to the surface and also a dominant component of the ground. Impacts therefore cause significant soft melt features, with craters often heavily distorted. Similarly, there is evidence of the existence of past mud volcanoes that once spewed water and mud from below ground.
In the south however the surface is at a higher elevation, and it appears the ice layer is deeper underground. Thus, it appears the ground is more firm, and the only obvious evidence of an underground layer of ice is revealed when sublimation and the subsequent erosion produce these large pits inside craters.
This very cursory look at Mars very tentatively suggests that future colonists will find it a bit harder to access ice in the southern mid-latitudes, while also finding it easier to build their colonies, since the ground will be firm with solid bedrock.
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.
Today is the last part in our four part exploration of the cratered southern highlands of Mars, begun last week. (For the early parts, go here-Part #1, here-Part #2, and here-Part #3.) Though there is no need, new readers should read the first three parts first, in order to get the larger perspective of this final post.
The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on December 20, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the eastern main gully descending down into a pit that sits in the north center of 52-mile-wide Asimov Crater, as shown in the inset on the overview map above. (For an MRO high resolution of the western gullies into this pit, see this January 2019 cool image post.)
Like Rabe Crater (also shown on the overview map) as well as all the craters around it as well as many near Asimov, the interior floor of Asimov crater is eroding away. Unlike those other craters highlighted in the previous parts of this series, today’s image shows the likely glacial ice nature of that erosion much more clearly. Note the parallel cracks cutting across the slope, all of which suggest that as the gully erodes the ice on its slope is also sagging downward, forming cracks as sections separate under the pressure of gravity. Since this region of the southern cratered highlands is all inside the 30 to 60 degree latitude band where scientists have generally found ample evidence of buried glaciers or ice, such glacier-like features should not surprise us.
Overall, our short survey of the southern cratered highlands suggests that the glacial material and ice found in the southern mid-latitudes affects the Martian surface differently than in the northern lowland plains. In the north the craters and the surrounding terrain often appear blobby, as if the ice is close to the surface and also a dominant component of the ground. Impacts therefore cause significant soft melt features, with craters often heavily distorted. Similarly, there is evidence of the existence of past mud volcanoes that once spewed water and mud from below ground.
In the south however the surface is at a higher elevation, and it appears the ice layer is deeper underground. Thus, it appears the ground is more firm, and the only obvious evidence of an underground layer of ice is revealed when sublimation and the subsequent erosion produce these large pits inside craters.
This very cursory look at Mars very tentatively suggests that future colonists will find it a bit harder to access ice in the southern mid-latitudes, while also finding it easier to build their colonies, since the ground will be firm with solid bedrock.
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
Readers: the rules for commenting!
No registration is required. I welcome all opinions, even those that strongly criticize my commentary.
However, name-calling and obscenities will not be tolerated. First time offenders who are new to the site will be warned. Second time offenders or first time offenders who have been here awhile will be suspended for a week. After that, I will ban you. Period.
Note also that first time commenters as well as any comment with more than one link will be placed in moderation for my approval. Be patient, I will get to it.