The layers of Mars’ north pole icecap
Click for full image.
Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on April 1, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the high cliff edge of the Martian north polar ice cap, and was taken as part of the springtime monitoring for the numerous avalanches that fall from the icecap’s steep edge every spring.
This particular cliff is probably about 1,000 feet high. I cannot tell if the image captured any avalanches on the very steep north-facing cliff. What struck me about this image however was the terraced layers so visible on the west-facing scarp. You can clearly count about eleven distinct and thick layers, each forming a wide ledge.
Each layer represents a different climate epoch on Mars when the ice cap was growing, with new snow being deposited.
The graph to the right, taken from this paper [pdf], shows how the rotational tilt of Mars, its obliquity, is believed to have shifted over the past 80 million years, that tilt shifting from as low as 11 degrees to as much as 47 degrees.
Scientists believe that when the tilt is low, the poles are the coldest places on Mars. At that time, these layers would be growing as the ice in the planet’s mid-latitudes sublimates into the atmosphere to fall as snow on the polar icecaps.
When the planet’s tilt was as high as 47 degrees, the mid-latitudes become the coldest region on Mars, and the ice on these polar layers begins to sublimate away to fall as snow in the mid-latitudes. The ice however did not all disappear, probably because dust had been deposited on top to protect it. When the obliquity shifted again and snow began falling at the pole, a new layer began to form on top of the dirty top of the previous layer, creating the layers we see today.
This image shows about eleven thick layers, each probably representing an epoch of at least several hundred thousand years. The retreat seen for each new layer probably tells us something about the overall loss of water in Mars’ atmosphere.
Other places along the icecap’s edge typically show many more layers, illustrating that the number of climate cycles on Mars have been very numerous over the eons. In order to get a clear picture of the geological history of all of Mars we will need to document these cycles precisely, a documentation that will not be possible until we can drill a number of core samples into this icecap so that we can date each layer.
Once we can do that, much of the geology we see here as well as in the mid-latitudes will suddenly become decipherable. The guesswork that planetary geologists are now making about what they see across all of the icy surface of Mars above 30 degrees latitude will change to solid knowledge and some clarity.
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 full image.
Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on April 1, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the high cliff edge of the Martian north polar ice cap, and was taken as part of the springtime monitoring for the numerous avalanches that fall from the icecap’s steep edge every spring.
This particular cliff is probably about 1,000 feet high. I cannot tell if the image captured any avalanches on the very steep north-facing cliff. What struck me about this image however was the terraced layers so visible on the west-facing scarp. You can clearly count about eleven distinct and thick layers, each forming a wide ledge.
Each layer represents a different climate epoch on Mars when the ice cap was growing, with new snow being deposited.
The graph to the right, taken from this paper [pdf], shows how the rotational tilt of Mars, its obliquity, is believed to have shifted over the past 80 million years, that tilt shifting from as low as 11 degrees to as much as 47 degrees.
Scientists believe that when the tilt is low, the poles are the coldest places on Mars. At that time, these layers would be growing as the ice in the planet’s mid-latitudes sublimates into the atmosphere to fall as snow on the polar icecaps.
When the planet’s tilt was as high as 47 degrees, the mid-latitudes become the coldest region on Mars, and the ice on these polar layers begins to sublimate away to fall as snow in the mid-latitudes. The ice however did not all disappear, probably because dust had been deposited on top to protect it. When the obliquity shifted again and snow began falling at the pole, a new layer began to form on top of the dirty top of the previous layer, creating the layers we see today.
This image shows about eleven thick layers, each probably representing an epoch of at least several hundred thousand years. The retreat seen for each new layer probably tells us something about the overall loss of water in Mars’ atmosphere.
Other places along the icecap’s edge typically show many more layers, illustrating that the number of climate cycles on Mars have been very numerous over the eons. In order to get a clear picture of the geological history of all of Mars we will need to document these cycles precisely, a documentation that will not be possible until we can drill a number of core samples into this icecap so that we can date each layer.
Once we can do that, much of the geology we see here as well as in the mid-latitudes will suddenly become decipherable. The guesswork that planetary geologists are now making about what they see across all of the icy surface of Mars above 30 degrees latitude will change to solid knowledge and some clarity.
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.
Almost like steps…
Fabulous image!
I always like seeing new information about the ice caps of Mars.
Has there ever been, or is there any present proposal, for mars landers to probe those regions?
Brad: In a word, no. We had a lander many years ago that tried to land near the poles, Mars Polar Lander, but the mission failed.