22 April 2011
New CO2 Reservoir Discovered on Mars
Posted by Ryan Anderson
Extrapolated thickness of the buried CO2 deposit near the south pole of Mars. Red is thicker, and it tapers to zero thickness (black). The thickness map is superposed on a geologic map of the south pole.
If you’ve followed Mars science for long, you know that the question of where the atmosphere went is a major one. Evidence points to liquid water on the surface of Mars, and that’s only possible if the atmospheric pressure is high enough and the surface temperature is warm enough. Adding CO2 to the atmosphere would increase both temperature and pressure, so a lot of scientists have been looking for carbonate rocks that might be trapping the CO2 that used to be in the atmosphere.
Well, this week a new article in Science reveals that there is a huge amount of CO2 trapped as dry ice near the South Pole! We’ve known for a long time that there is a residual CO2 ice cap near the martian south pole, but it is pretty small. The new discovery uses ground-penetrating radar to reveal a buried deposit of CO2 with a volume comparable to Lake Superior. Put another way, there is 80% as much CO2 trapped in this deposit as there is in the martian atmosphere.
As Mars’ axial tilt changes, deposits like this grow and shrink, so this means that the atmospheric thickness changes significantly. A thicker atmosphere in turn makes the planet warmer and makes it easier to have liquid water on the surface. Evidence suggests that the deposit is currently sublimating, so the current martian atmosphere is gradually getting thicker.
This is a really cool result! Everyone has been so focused on looking for carbonates that it’s great to see a new source of CO2 that can partially explain a thicker past atmosphere. Mars is still full of surprises!
Yes, but for this being a “hot” result you may need the newly found buried carbonates too, going _way_ back into Mars history:
“”A tilted Mars with a thicker carbon-dioxide atmosphere causes a greenhouse effect that tries to warm the Martian surface, while thicker and longer-lived polar ice caps try to cool it,” said co-author Robert Haberle, a planetary scientist at NASA’s Ames Research Center in Moffett Field, Calif. “Our simulations show the polar caps cool more than the greenhouse warms. Unlike Earth, which has a thick, moist atmosphere that produces a strong greenhouse effect, Mars’ atmosphere is too thin and dry to produce as strong a greenhouse effect as Earth’s, even when you double its carbon-dioxide content.””
http://www.nasa.gov/mission_pages/MRO/news/mro20110421.html
Atmospheres! Can’t live with them, can’t live without them.
Actually, even these (though no models backing up):
“Although the newly found reservoir could nearly double the mass of carbon dioxide in Mars’s atmosphere, the resulting climate alterations would be “modest” and would not generate a warmer, wetter Mars, notes Peter Thomas of Cornell University in a commentary also posted online April 21 in Science.
Phillips concurs and notes that during times of higher tilt, more carbon dioxide frost would settle on the planet’s surface. The reflectivity of the surface frost, along with other effects, would offset any greenhouse warming from the extra gas in the atmosphere, and would tend to maintain the chilly temperatures now typical on the Red Planet.”
http://www.sciencenews.org/view/generic/id/73147/title/Dry_ice%2C_wetter_Mars_