A cliff face of volcanic erosion on Mars
Click for full image.
Today’s cool image is a variation of yesterday’s, showing another area on the edge of Mars’ largest volcanic ash field, dubbed the Medusae Fossae Formation and about the size of India. This time however the edge is an abrupt cliff, not the slow petering out of wind-shaped mesas.
The picture to the right, cropped, reduced, and sharpened to post here, was taken on August 27, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what I very roughly estimate to be a 1,500 to 2,500 foot high cliff that appears to delineate the edge. To the north we have a plateau of intersperse layers of flood lava and ash. To the south those layers have eroded away, leaving a rough lava plain with a handful of scattered wind-sculpted mesas.
The overview map below, by providing a wider view of his region, makes its nature clearer.
The white cross marks the location of today’s photo. The inset provides a more detailed view of this region. As with yesterday’s cool image, this photo shows a spot near the northern edge of the Medusae Fossae Formation. Here however the ash field is eroding away not like a dune field but in chunks, producing distinct but randomly distributed canyons. Based on the shape of the few mesas, the prevailing wind here appears to come from the southeast.
The central geological question is this: Why did the erosion in this part of the Medusae ash field produce such an abrupt cliff, and not a more gradual change as in yesterday’s image? The canyons and cliffs suggest a faster and more violent cause for the erosion, which further suggests that while wind played the dominant role in yesterday’s picture, in today’s image we could be seeing evidence of either glacial or liquid erosion.
As always, I am as an uneducated tourist merely guessing. The cause in the difference could also simply be a difference in the nature of the ash and lava. Yesterday’s ash could be more like sandstone, and thus break up more easily by the wind. Today’s ash might be stronger structurally, with solid layers of lava holding it together. Thus, wind still does the job, but it only erodes the ash when a large piece breaks off, rather then when tiny sand particles are blown away.
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. from any other book seller, or direct from my ebook publisher, ebookit.
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’s cool image is a variation of yesterday’s, showing another area on the edge of Mars’ largest volcanic ash field, dubbed the Medusae Fossae Formation and about the size of India. This time however the edge is an abrupt cliff, not the slow petering out of wind-shaped mesas.
The picture to the right, cropped, reduced, and sharpened to post here, was taken on August 27, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what I very roughly estimate to be a 1,500 to 2,500 foot high cliff that appears to delineate the edge. To the north we have a plateau of intersperse layers of flood lava and ash. To the south those layers have eroded away, leaving a rough lava plain with a handful of scattered wind-sculpted mesas.
The overview map below, by providing a wider view of his region, makes its nature clearer.
The white cross marks the location of today’s photo. The inset provides a more detailed view of this region. As with yesterday’s cool image, this photo shows a spot near the northern edge of the Medusae Fossae Formation. Here however the ash field is eroding away not like a dune field but in chunks, producing distinct but randomly distributed canyons. Based on the shape of the few mesas, the prevailing wind here appears to come from the southeast.
The central geological question is this: Why did the erosion in this part of the Medusae ash field produce such an abrupt cliff, and not a more gradual change as in yesterday’s image? The canyons and cliffs suggest a faster and more violent cause for the erosion, which further suggests that while wind played the dominant role in yesterday’s picture, in today’s image we could be seeing evidence of either glacial or liquid erosion.
As always, I am as an uneducated tourist merely guessing. The cause in the difference could also simply be a difference in the nature of the ash and lava. Yesterday’s ash could be more like sandstone, and thus break up more easily by the wind. Today’s ash might be stronger structurally, with solid layers of lava holding it together. Thus, wind still does the job, but it only erodes the ash when a large piece breaks off, rather then when tiny sand particles are blown away.
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. from any other book seller, or direct from my ebook publisher, ebookit. 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.