Martian Atmospheric Erosion Rates
Stas Barabash,1*
Andrei Fedorov,2
Rickard Lundin,1
Jean-Andre Sauvaud2
Mars was once wet but is now dry, and the fate of its ancient
carbon dioxide atmosphere is one of the biggest puzzles in martian
planetology. We have measured the current loss rate due to the
solar wind interaction for different species: Q(O
+) = 1.6·10
23 per second = 4 grams per second (g s
–1), Q(O
+2) = 1.5·10
23 s
–1 = 8 g s
–1, and Q(CO
+2) = 8·10
22 s
–1 = 6 g s
–1 in the energy range of 30 to 30,000 electron
volts per charge. These rates can be propagated backward over
a period of 3.5 billion years, resulting in the total removal
of 0.2 to 4 millibar of carbon dioxide and a few centimeters
of water. The escape rate is low, and thus one has to continue
searching for water reservoirs and carbon dioxide stores on
or beneath the planetary surface and investigate other escape
channels.
2 Centre d'Etude Spatiale des Rayonnements, BP-4346, F-31028 Toulouse, France.
* To whom correspondence should be addressed. E-mail: stas{at}irf.se
