Exploring the cratered southern highlands of Mars, part 2
Click for original image.
Our travels in the cratered southern highlands of Mars continues. Today we visit 67-mile-wide Rabe Crater, as indicated on the overview map above. The picture to the right, cropped and reduced to post here, was taken on January 27, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).
Rabe Crater is significant for several reasons. First, it was one of the first places on Mars where sand dunes were identified, by one of the Viking orbiters in the late 1970s [pdf]. Second, the pits and sand in its interior, are unusual and puzzling. The inset on the overview map provides a closeup look at the crater. The yellow mound in the central south of the crater floor is all dunes, which are surrounded by the pit with steep cliffs more than a 1,000 feet high.
The sudden change in color in the picture clearly shows the contact between these dunes and a section of bedrock that sticks up above them. Likely this difference is caused by the nature of the material, with the dunes made of fine-grained sand and the bedrock coarse rock.
Present theory suggests that the sand in the dunes comes from the large surrounding pit, though this is not confirmed. The pit itself is thought to have been formed by either water or glacial erosion, though neither of these theories are confirmed as well.
What is most intriguing is the lack of obvious glacial material inside Rabe Crater, even though it is located at 43 degrees south latitude, where such glacial features are common in craters, and where just a short distance to the southwest (where yesterday’s cool image was located), the ground seems completely ice covered. Possibly the crater’s high elevation plays a part, but if so why are there glacial features in other craters at the same elevations, as well as on the plains nearby? Some researchers think the impact that formed Hellas Basin might be part of the answer, though this explanation depends on so many assumptions it cannot be taken too seriously.
More on this subject tomorrow, when we visit another crater in this region with similar features.
Readers!
Please consider supporting my work here at Behind the Black. Your support allows me the freedom and ability to analyze objectively the ongoing renaissance in space, as well as the cultural changes -- for good or ill -- that are happening across America. Fourteen years ago I wrote that SLS and Orion were a bad ideas, a waste of money, would be years behind schedule, and better replaced by commercial private enterprise. Only now does it appear that Washington might finally recognize this reality.
In 2020 when the world panicked over COVID I wrote that the panic was unnecessary, that the virus was apparently simply a variation of the flu, that masks were not simply pointless but if worn incorrectly were a health threat, that the lockdowns were a disaster and did nothing to stop the spread of COVID. Only in the past year have some of our so-called experts in the health field have begun to recognize these facts.
Your help allows me to do this kind of intelligent analysis. I take no advertising or sponsors, so my reporting isn't influenced by donations by established space or drug companies. Instead, I rely entirely on donations and subscriptions from my readers, which gives me the freedom to write what I think, unencumbered by outside influences.
You can support me either by giving a one-time contribution or a regular subscription. There are four ways of doing so:
1. Zelle: This is the only internet method that charges no fees. All you have to do is use the Zelle link at your internet bank and give my name and email address (zimmerman at nasw dot org). What you donate is what I get.
2. Patreon: Go to my website there and pick one of five monthly subscription amounts, or by making a one-time donation.
3. A Paypal Donation or subscription:
4. Donate by check, payable to Robert Zimmerman and mailed to
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652
You can also support me by buying one of my books, as noted in the boxes interspersed throughout the webpage or shown in the menu above.
Click for original image.
Our travels in the cratered southern highlands of Mars continues. Today we visit 67-mile-wide Rabe Crater, as indicated on the overview map above. The picture to the right, cropped and reduced to post here, was taken on January 27, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).
Rabe Crater is significant for several reasons. First, it was one of the first places on Mars where sand dunes were identified, by one of the Viking orbiters in the late 1970s [pdf]. Second, the pits and sand in its interior, are unusual and puzzling. The inset on the overview map provides a closeup look at the crater. The yellow mound in the central south of the crater floor is all dunes, which are surrounded by the pit with steep cliffs more than a 1,000 feet high.
The sudden change in color in the picture clearly shows the contact between these dunes and a section of bedrock that sticks up above them. Likely this difference is caused by the nature of the material, with the dunes made of fine-grained sand and the bedrock coarse rock.
Present theory suggests that the sand in the dunes comes from the large surrounding pit, though this is not confirmed. The pit itself is thought to have been formed by either water or glacial erosion, though neither of these theories are confirmed as well.
What is most intriguing is the lack of obvious glacial material inside Rabe Crater, even though it is located at 43 degrees south latitude, where such glacial features are common in craters, and where just a short distance to the southwest (where yesterday’s cool image was located), the ground seems completely ice covered. Possibly the crater’s high elevation plays a part, but if so why are there glacial features in other craters at the same elevations, as well as on the plains nearby? Some researchers think the impact that formed Hellas Basin might be part of the answer, though this explanation depends on so many assumptions it cannot be taken too seriously.
More on this subject tomorrow, when we visit another crater in this region with similar features.
Readers!
Please consider supporting my work here at Behind the Black. Your support allows me the freedom and ability to analyze objectively the ongoing renaissance in space, as well as the cultural changes -- for good or ill -- that are happening across America. Fourteen years ago I wrote that SLS and Orion were a bad ideas, a waste of money, would be years behind schedule, and better replaced by commercial private enterprise. Only now does it appear that Washington might finally recognize this reality.
In 2020 when the world panicked over COVID I wrote that the panic was unnecessary, that the virus was apparently simply a variation of the flu, that masks were not simply pointless but if worn incorrectly were a health threat, that the lockdowns were a disaster and did nothing to stop the spread of COVID. Only in the past year have some of our so-called experts in the health field have begun to recognize these facts.
Your help allows me to do this kind of intelligent analysis. I take no advertising or sponsors, so my reporting isn't influenced by donations by established space or drug companies. Instead, I rely entirely on donations and subscriptions from my readers, which gives me the freedom to write what I think, unencumbered by outside influences.
You can support me either by giving a one-time contribution or a regular subscription. There are four ways of doing so:
1. Zelle: This is the only internet method that charges no fees. All you have to do is use the Zelle link at your internet bank and give my name and email address (zimmerman at nasw dot org). What you donate is what I get.
2. Patreon: Go to my website there and pick one of five monthly subscription amounts, or by making a one-time donation.
3. A Paypal Donation or subscription:
4. Donate by check, payable to Robert Zimmerman and mailed to
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652
You can also support me by buying one of my books, as noted in the boxes interspersed throughout the webpage or shown in the menu above.
More on Mars
https://phys.org/news/2023-04-interactive-mosaic-nasa-imagery-mars.html