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+) = 1.6·1023 per second = 4 grams per second (g s–1), Q(O +2) = 1.5·1023 s–1 = 8 g s–1, and Q(CO +2) = 8·1022 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.
1 Swedish Institute of Space Physics, Box 812, 98128 Kiruna, Sweden.
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
