Content uploaded by Carmen Córdoba-Jabonero
Author content
All content in this area was uploaded by Carmen Córdoba-Jabonero
Content may be subject to copyright.
Assessments for possible habitability in Martian polar environments: Fundaments based in ice screening of UV radiation
Abstract
We present a study of the solar UV radiation in Martian high latitude environments covered by ice, where the UV propagation through the polar cover depends on the ice radiative properties (layers of H 2O or CO 2 ice). But also we will investigate the changes in the subsurface UV levels induced by the seasonal variations of solar UV flux on the surface, as well as by the seasonal freezing-thawing and related CO 2 sublimation processes. The biological dose relative to DNA-damage will be also estimated for biological implication assessments. All these studies will be compared with the biological dose received in the Antarctic snow-ice covered environment which is seasonally exposed to high UV radiation levels (formation of "ozone hole"), where the environmental conditions could be similar to those present on Mars (Cockell et al., 2002; Cockell and Córdoba-Jabonero, 2004).
ResearchGate has not been able to resolve any citations for this publication.
The Martian environment has an exceedingly strong component of damaging solar far-ultraviolet radiation, including most of the UV-C range (190–280 nm) because of the lack of an e7ective ozone shield. Two-stream radiative transfer modelling, including particulate aerosol content and surface albedo, indicates that the present abundance of SO2 does not provide any surface protection of the UV radiation. However, larger abundances of sulfur dioxide (mixing ratio, q, comprised between 10-5 and 10-4) introduced in the present 6 mbar Martian atmosphere can partially protect the surface from the harmful solar UV radiation. Furthermore, Mie backscattering by dust and/or aerosols noticeably reduces the harmful solar UV radiation. Regardless of the ozone concentration, the required dust content for almost blocking this damaging radiation is such that the optical depth at 550 nm is AOD=0:8–1.5 (for a given solar zenithal angle (SZA) of 38º), typical of a turbid atmosphere, and AOD > 1.6 more characteristic of dust storms. The required mass of SO2 (i.e. 10+14–10+15 gr) and/or ashes could have been easily provided by volcanic activity on Mars several times along the entire geologic history of the planet. In terms of DNA protection, volcanic ashes and SO2 considerably reduced levels of UV radiation lead to a biological dose comparable to the existing on the present Earth, together with the possibility of a non-deterioration of the environment due to UV photo-oxidation. Therefore, preserving life forms on Mars surface at any past epoch cannot be completely ruled out.