Erosion at the edge of Mars’ biggest volcanic ash field
Click for full image.
Cool image time! The photo to the right, rotated, cropped, reduced, and sharpened to post here, was taken on August 13, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It is another fine example of the wind-blown sculpted terrain that one finds routinely in Mars’ largest volcanic ash field, dubbed the Medusae Fossae Formation. About the size of India, this gigantic field is thought to be the source of most of the dust on Mars.
This particular location sits on the northernmost edge of that huge field. The elongated mesas mark the field’s edge, disappearing to the north but becoming thick and extensive to the south. The prevailing southeast-to-northwest winds have acted to clean most of the ash away.
We can get an idea about how deep and pervasive that field once was at this location by the pedestal crater in the middle right. Once, the floor of that crater was below the top of the ash field. At that time, the top of the dunes marked the general ground level across this entire image. Over time, the winds blew most of this material away, but the denser packed floor of the crater resisted that erosion, and thus now stands above the surrounding terrain.
The more normal-looking craters nearby could have occurred before the ash was deposited, or after it was blown away. The impact that created the pedestal crater however occurred when the ash covered everything here.
The white cross on the overview map to the right marks the location of this image. If you look close at the full resolution image, you will see that these mesas are made up of multiple layers, with each layer likely the result of a nearby major volcanic eruption from one of the many mammoth volcanoes to the east and west. The flat terrain on which they sit is likely a hard lava flood plain, not ash. This flood lava was likely laid down first, then covered with the volcanic ash, which has now 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 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 full image.
Cool image time! The photo to the right, rotated, cropped, reduced, and sharpened to post here, was taken on August 13, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It is another fine example of the wind-blown sculpted terrain that one finds routinely in Mars’ largest volcanic ash field, dubbed the Medusae Fossae Formation. About the size of India, this gigantic field is thought to be the source of most of the dust on Mars.
This particular location sits on the northernmost edge of that huge field. The elongated mesas mark the field’s edge, disappearing to the north but becoming thick and extensive to the south. The prevailing southeast-to-northwest winds have acted to clean most of the ash away.
We can get an idea about how deep and pervasive that field once was at this location by the pedestal crater in the middle right. Once, the floor of that crater was below the top of the ash field. At that time, the top of the dunes marked the general ground level across this entire image. Over time, the winds blew most of this material away, but the denser packed floor of the crater resisted that erosion, and thus now stands above the surrounding terrain.
The more normal-looking craters nearby could have occurred before the ash was deposited, or after it was blown away. The impact that created the pedestal crater however occurred when the ash covered everything here.
The white cross on the overview map to the right marks the location of this image. If you look close at the full resolution image, you will see that these mesas are made up of multiple layers, with each layer likely the result of a nearby major volcanic eruption from one of the many mammoth volcanoes to the east and west. The flat terrain on which they sit is likely a hard lava flood plain, not ash. This flood lava was likely laid down first, then covered with the volcanic ash, which has now 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 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