The reasons why Mars two polar caps are so different
The Martian north pole.
The Martian south pole.
What the colors mean in terms of elevation
A new paper, in review for the past year, has now been published describing the differences between the north and south poles of Mars, the most fundamental of which involve the planet’s orbit and the different elevations of the two poles, with the south pole three to six miles higher in altitude (as indicated by the colors on the maps to the right).
The cumulative data has allowed the researchers to explain why — when the thin winter cap of dry ice sublimates away in the spring — the process at the south pole results in spiderlike features that get enhanced from year to year, but in the north pole that sublimation process produces no such permanent features.
In both cases, the spring sunlight passes through the clear winter mantle of dry ice to heat its base. The sublimated trapped CO2 gas builds up, until the pressure causes the mantle to crack at weak spots. In the south that trapped gas flows uphill each spring along the same paths, carving the riverlike tributaries dubbed unofficially as “spiders” and officially as “araneiform terrain.”
Geophysicist Hugh Kieffer described that process in 2006. A few years later, [Candice] Hansen [the new paper’s lead author] followed up with her own model for the north polar cap, which also displays fans in the spring.
She found that the same phenomena occur in the north, but rather than relatively flat terrain, these processes play out across sand dunes. “When the Sun comes up and begins to sublimate the bottom of the ice layer, there are three weak spots – one at the crest of the dune, one at the bottom of the dune where it meets the surface and then the ice itself can crack along the slope,” Hansen said. “No araneiform terrain has been detected in the north because although shallow furrows develop, the wind smooths the sand on the dunes.”
There is also a lot more dust in the north, including a giant sea of dunes that circles the polar cap. In addition, the northern winter is shorter due to the planet’s orbit, and takes place during the annual dust storm season, causing there to be more dust concentrated within the northern ice. All of these factors make the the dunes and general surface in the north is more easily smoothed by the wind.
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The Martian north pole.
The Martian south pole.
What the colors mean in terms of elevation
A new paper, in review for the past year, has now been published describing the differences between the north and south poles of Mars, the most fundamental of which involve the planet’s orbit and the different elevations of the two poles, with the south pole three to six miles higher in altitude (as indicated by the colors on the maps to the right).
The cumulative data has allowed the researchers to explain why — when the thin winter cap of dry ice sublimates away in the spring — the process at the south pole results in spiderlike features that get enhanced from year to year, but in the north pole that sublimation process produces no such permanent features.
In both cases, the spring sunlight passes through the clear winter mantle of dry ice to heat its base. The sublimated trapped CO2 gas builds up, until the pressure causes the mantle to crack at weak spots. In the south that trapped gas flows uphill each spring along the same paths, carving the riverlike tributaries dubbed unofficially as “spiders” and officially as “araneiform terrain.”
Geophysicist Hugh Kieffer described that process in 2006. A few years later, [Candice] Hansen [the new paper’s lead author] followed up with her own model for the north polar cap, which also displays fans in the spring.
She found that the same phenomena occur in the north, but rather than relatively flat terrain, these processes play out across sand dunes. “When the Sun comes up and begins to sublimate the bottom of the ice layer, there are three weak spots – one at the crest of the dune, one at the bottom of the dune where it meets the surface and then the ice itself can crack along the slope,” Hansen said. “No araneiform terrain has been detected in the north because although shallow furrows develop, the wind smooths the sand on the dunes.”
There is also a lot more dust in the north, including a giant sea of dunes that circles the polar cap. In addition, the northern winter is shorter due to the planet’s orbit, and takes place during the annual dust storm season, causing there to be more dust concentrated within the northern ice. All of these factors make the the dunes and general surface in the north is more easily smoothed by the wind.
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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