22 April 2011
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!