Meandering ridges in Greg Crater
Click for original image.
Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on November 29, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label “curved ridges.”
These might be inverted channels, the beds on which either water or ice flowed, compacting it down so that it became very resistant to erosion, and thus remains when the surrounding terrain was worn away. However, none of them seem to follow any grade. A more likely explanation is that these are ancient moraines, the debris pile pushed ahead of a glacier and then left behind when the glacier goes away.
The location is the reason I favor this explanation.
The black dot inside Greg Crater on the right edge of the overview map to the right marks this picture’s location. The latitude is 39 degrees south, not only well inside the 30-60 degree latitude band where orbital images find many glaciers on Mars, but also in a region to the east of Hellas Basin that scientists have specifically labeled as having numerous glacial features.
Many pictures in this region show similar meandering ridges. See for example this cool image from January 2021 of the north interior rim of of this same crater. See also this picture from November 2022. The second is especially similar to today’s meandering ridges, except that its position paralleling its crater interior wall makes it very clear it is a moraine.
In today’s image, the parallel ridges instead suggest that there were actually two glaciers here once, moving downhill towards each other. The space between the two longest ridges actually appears to be the low point in the southern quadrant of Greg Crater. The two glaciers never quite collided, but instead left opposing moraines only about 1,500 to 2,000 feet apart.
The third ridge to the west, partly destroyed by the impact crater that came later, suggests that there were cycles of glacial growth and decline. Other images suggest that the pattern was that during each growth period the glaciers on Mars grew less, as if there was less water to feed them.
Nonetheless, there are still glaciers in Greg Crater, not only as indicated by the January 2021 image of the glaciers along its north interior rim but by the glacial features seen on the inside of the impact crater on the left of today’s picture.
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:
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Click for original image.
Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on November 29, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label “curved ridges.”
These might be inverted channels, the beds on which either water or ice flowed, compacting it down so that it became very resistant to erosion, and thus remains when the surrounding terrain was worn away. However, none of them seem to follow any grade. A more likely explanation is that these are ancient moraines, the debris pile pushed ahead of a glacier and then left behind when the glacier goes away.
The location is the reason I favor this explanation.
The black dot inside Greg Crater on the right edge of the overview map to the right marks this picture’s location. The latitude is 39 degrees south, not only well inside the 30-60 degree latitude band where orbital images find many glaciers on Mars, but also in a region to the east of Hellas Basin that scientists have specifically labeled as having numerous glacial features.
Many pictures in this region show similar meandering ridges. See for example this cool image from January 2021 of the north interior rim of of this same crater. See also this picture from November 2022. The second is especially similar to today’s meandering ridges, except that its position paralleling its crater interior wall makes it very clear it is a moraine.
In today’s image, the parallel ridges instead suggest that there were actually two glaciers here once, moving downhill towards each other. The space between the two longest ridges actually appears to be the low point in the southern quadrant of Greg Crater. The two glaciers never quite collided, but instead left opposing moraines only about 1,500 to 2,000 feet apart.
The third ridge to the west, partly destroyed by the impact crater that came later, suggests that there were cycles of glacial growth and decline. Other images suggest that the pattern was that during each growth period the glaciers on Mars grew less, as if there was less water to feed them.
Nonetheless, there are still glaciers in Greg Crater, not only as indicated by the January 2021 image of the glaciers along its north interior rim but by the glacial features seen on the inside of the impact crater on the left of today’s picture.
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.
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