Computer Science
Scientific paper
Jul 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994metic..29r.485k&link_type=abstract
Meteoritics (ISSN 0026-1114), vol. 29, no. 4, p. 485-486
Computer Science
Atmospheric Composition, Carbonates, Irradiation, Mars Surface, Sulfates, Ultraviolet Radiation, Chemical Effects, Mass Spectroscopy, Radiation Effects, Weathering, Wind Effects
Scientific paper
The martian surface is exposed to both short-wavelength solar irradiation and intensive windblown dust-particle bombardment. These factors can cause alterations of martian soil surface layers due to photochemical weathering and wind abrasion. However, no information is available about the stability of volatile-bearing martian salts like carbonates and sulfates under solar irradiation in Mars-like condition. Impact-stimulated devolatilization of these salts was investigated only for high-energy impact conditions simulating meteorite bombardment. We have investigated the decomposition of CaCO3 and MgSO4 surfaces during UV-irradiation and low-energy impact in laboratory conditions by means of mass spectrometry and thermodesorption spectroscopy. During irradiation of powder and monocrystal carbonate samples at temperatures 200-600 K, we observed CO2 release with the efficiencies of 10-6-10-4 molecules/photon depending on temperature, photon energy, and history of the surface. During this annealing of irradiated sample the desorption of an additional amount of stored CO2 was observed due to a thermostimulated relaxation process in the surface layer damaged by UV. Photoinduced production of SO2 under UV illumination of the sulfate samples was detected. We also observed the strong promotion effect of adsorbed H2O on SO2 production under illumination that can take place under real martian conditions. The impact-induced devolatilization experiments revealed the release of CO2 during mechanical treatment of CaCO3 at room temperature. However, no SO2 was released during impact of MgSO4. We also obtained some indirect evidence of impact-induced partial chemical transformation of sulfate to carbonate after the impact of MgSO4 in a low-pressure CO2 atmosphere. Some quantitative estimations of the possible influence of the photo- and impact-induced weathering processes on the martian surface and atmosphere compositions are presented.
Dikov Yu. P.
HUTH John
Koscheev A. P.
Mukhin Lev M.
Wanke Heinrich
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