The wavy and beautiful edge of the northern ice cap of Mars
Click for full image.
Cool image time! The photo to the right, cropped and reduced to post here, was taken on August 7, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the many layered scarp that forms the edge of the northern polar ice cap on Mars, probably more than 2,000 feet high.
Those layers are significant, as they indicate the many climate cycles that scientists think Mars has undergone over the eons as the red planet’s rotational tilt, or obliquity, rocked back and forth from 11 degrees inclination to as much as 60 degrees. At the extremes, the ice cap was either growing or shrinking, while today (at 25 degrees inclination) it appears to be in a steady state.
Why the layers alternate light and dark is not known. The shift from lighter colors at the top half and the dark bottom half marks the separation between the top water ice cap and what scientists label the basal unit. It also marks some major change in Mars’ climate and geology that occurred about 4.5 million years ago.
The yellow cross on the overview map to the right indicates the location of this scarp. Because the pole’s scarps near the bottom of this map, where this photo was taken, tend to be less steep, most of the seasonal avalanches that occur in the spring are found along the scarps near the top of the map.
The origin of the hollow, where the scarp is retreating faster, is also unknown. For some reason something caused more erosion at this point. If it was an avalanche in the far past, all evidence of that event is gone. That the basal unit shows no such erosion suggests the origin is much more complicated than an avalanche.
One not obvious detail about this part of Mars is its daily weather. Though this is springtime and the Sun is out, it is very cold here, far colder than the coldest places on Earth. Though temperatures can get above freezing in the equatorial regions, at the poles that almost never happens. The planet’s average temperature globally is -81 degrees Fahrenheit. This means that at this spot the temperature when this photo was taken was likely well below zero degrees Fahrenheit, probably by many tens of degrees.
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.
Cool image time! The photo to the right, cropped and reduced to post here, was taken on August 7, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the many layered scarp that forms the edge of the northern polar ice cap on Mars, probably more than 2,000 feet high.
Those layers are significant, as they indicate the many climate cycles that scientists think Mars has undergone over the eons as the red planet’s rotational tilt, or obliquity, rocked back and forth from 11 degrees inclination to as much as 60 degrees. At the extremes, the ice cap was either growing or shrinking, while today (at 25 degrees inclination) it appears to be in a steady state.
Why the layers alternate light and dark is not known. The shift from lighter colors at the top half and the dark bottom half marks the separation between the top water ice cap and what scientists label the basal unit. It also marks some major change in Mars’ climate and geology that occurred about 4.5 million years ago.
The yellow cross on the overview map to the right indicates the location of this scarp. Because the pole’s scarps near the bottom of this map, where this photo was taken, tend to be less steep, most of the seasonal avalanches that occur in the spring are found along the scarps near the top of the map.
The origin of the hollow, where the scarp is retreating faster, is also unknown. For some reason something caused more erosion at this point. If it was an avalanche in the far past, all evidence of that event is gone. That the basal unit shows no such erosion suggests the origin is much more complicated than an avalanche.
One not obvious detail about this part of Mars is its daily weather. Though this is springtime and the Sun is out, it is very cold here, far colder than the coldest places on Earth. Though temperatures can get above freezing in the equatorial regions, at the poles that almost never happens. The planet’s average temperature globally is -81 degrees Fahrenheit. This means that at this spot the temperature when this photo was taken was likely well below zero degrees Fahrenheit, probably by many tens of degrees.
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
Is it my imagination, or is the ice cap generally spiral in structure especially near the pole? Aware of any speculation / hypothesis as to why that might be? Coriolis effect? (but I’ve never heard it applied to solid structures)
Greg the Geologist: I remember reading a paper somewhere discussing this. Your impression is correct. See this post on BtB:
https://behindtheblack.com/behind-the-black/points-of-information/mars-polar-ice-canyons-are-young-and-the-source-for-mid-latitude-ice/
Greg the Geologist: “Coriolis effect? (but I’ve never heard it applied to solid structures)”
The CO2 and water vapor from which the ices condense are gases, not a solid, and thus would respond to coriolis forces. The deposition of the condensates could mimic the flow patterns of the gases.
So Mars dose have Ice Cap proof of moister on Mars and where Marvin and K_9 go skinig