The strange carbon dioxide ice cap of Mars’ south pole
Click for original image.
Cool image time! The picture to the right, cropped to post here, was taken on July 1, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The image is labeled simply as a “terrain sample,” which usually means it was taken not as part of any specific research project but to fill a gap in the picture-taking schedule in order to maintain the camera’s proper temperate. When the camera team needs to do this, they try to picture interesting features availabe at that time slot. Sometimes the image is boring. Sometimes it is surprisingly interesting.
In this case the picture is the latter, and certainly quite alien. The curly parallel dark lines appear to be grooves, and seem to have ripple dunes within them, as if the only dust here got trapped in those low spots. It is also possible that the dunes are frozen and ancient, and are only being revealed as the top layer in each groove goes away.
What could possibly explain what we are looking at? The overview map below gives only a clue.
On the overview map to the right, the black dot in the middle of the ice cap of dry ice that lies on top of Mars south pole cap of water ice marks this location.
We are looking at a very large sheet of permanent dry ice, something we on Earth never see in a natural form. On Earth the temperatures are generally too warm for carbon dioxide to remain in its solid form, and so it quickly sublimates into gas if left out unprotected.
On Mars however the temperature and thin atmosphere is cold enough for dry ice to survive on the surface. For example, each winter the CO2 in the atmosphere falls as snow and forms a thin mantle of dry ice over both poles, from 60 degrees latitude and higher, only to sublimate back into the atmosphere with the coming of spring.
At the south pole however there is also a permanent ice cap of dry ice, as shown in white on the map to the right. Why the south pole has this permanent dry ice but the north pole does not is likely related to the different elevations and conditions between the poles, though the exact details are not yet understood.
Why this dry ice however forms these strange parallel lines is even less understood. Data from MRO images over many years suggest that dry ice cap is sublimating away, but generally that process looks very different than we see here.
As I have said many times, Mars is strange, Mars is wonderful, but above all, Mars is alien.
The support of my readers through the years has given 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. Four years ago, just before the 2020 election I wrote that Joe Biden's mental health was suspect. Only in this year has the propaganda mainstream media decided to recognize that basic fact.
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. Even today NASA and Congress refuse to 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.
Please consider supporting my work here at Behind the Black.
You can support me either by giving a one-time contribution or a regular subscription. There are five 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.
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5. Donate by check, payable to Robert Zimmerman and mailed to
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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. And if you buy the books through the ebookit links, I get a larger cut and I get it sooner.
Click for original image.
Cool image time! The picture to the right, cropped to post here, was taken on July 1, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The image is labeled simply as a “terrain sample,” which usually means it was taken not as part of any specific research project but to fill a gap in the picture-taking schedule in order to maintain the camera’s proper temperate. When the camera team needs to do this, they try to picture interesting features availabe at that time slot. Sometimes the image is boring. Sometimes it is surprisingly interesting.
In this case the picture is the latter, and certainly quite alien. The curly parallel dark lines appear to be grooves, and seem to have ripple dunes within them, as if the only dust here got trapped in those low spots. It is also possible that the dunes are frozen and ancient, and are only being revealed as the top layer in each groove goes away.
What could possibly explain what we are looking at? The overview map below gives only a clue.
On the overview map to the right, the black dot in the middle of the ice cap of dry ice that lies on top of Mars south pole cap of water ice marks this location.
We are looking at a very large sheet of permanent dry ice, something we on Earth never see in a natural form. On Earth the temperatures are generally too warm for carbon dioxide to remain in its solid form, and so it quickly sublimates into gas if left out unprotected.
On Mars however the temperature and thin atmosphere is cold enough for dry ice to survive on the surface. For example, each winter the CO2 in the atmosphere falls as snow and forms a thin mantle of dry ice over both poles, from 60 degrees latitude and higher, only to sublimate back into the atmosphere with the coming of spring.
At the south pole however there is also a permanent ice cap of dry ice, as shown in white on the map to the right. Why the south pole has this permanent dry ice but the north pole does not is likely related to the different elevations and conditions between the poles, though the exact details are not yet understood.
Why this dry ice however forms these strange parallel lines is even less understood. Data from MRO images over many years suggest that dry ice cap is sublimating away, but generally that process looks very different than we see here.
As I have said many times, Mars is strange, Mars is wonderful, but above all, Mars is alien.
The support of my readers through the years has given 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. Four years ago, just before the 2020 election I wrote that Joe Biden's mental health was suspect. Only in this year has the propaganda mainstream media decided to recognize that basic fact.
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. Even today NASA and Congress refuse to 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.
Please consider supporting my work here at Behind the Black.
You can support me either by giving a one-time contribution or a regular subscription. There are five 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:
5. 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. And if you buy the books through the ebookit links, I get a larger cut and I get it sooner.
Cool looking Mars maze. I couldn’t find any easy way through.
All I could think of for how it formed was a half billion years or so of freezer-burn/sublimation. BTW – CO2 ice crystals are about 100x smaller than H2O ice crystals/flakes, and very densely packed (cuboctahedral).
I discovered a package of freezer-burn sausages starting look similar after a couple of months at the bottom of my freezer.