Sterilisation properties of the Mars surface and atmospheric environment

The radiative and chemical conditions at the surface and in the lower Martian atmosphere are computed at various latitudes and seasons combining a 2D photochemical model and radiation simulations. In most situations, the solar UV B and C radiations reach the surface however, suspended dust and, in polar cases, ozone can constitute an effective UV shield. The daytime and night time concentrations of the sterilizing oxidants: OH, H2O2 and O-3 are determined, as well as the concentration of the substances which could influence the metabolism of microorganisms. The possible habitats of a remaining Mars's life as well as the possibilities of contamination by resistant earth life forms will be described. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.