Exobiological implications of potential sedimentary deposits on Mars

One of main objectives of Mars exploration in the 21st century is to search for evidence of present or ancient life. Sedimentary processes are importa nt on the Martian surface. However, styles of Martian sedimentation can be different from its terrestrial counterpart in some aspects because of the r elatively stable Martian crust and the lack of a continuous and active surf ace hydrological cycle. Certain types of sedimentary deposits on Earth are closely linked to biological activities, and searching for such deposits on Mars can potentially enhance the chance of finding life or evidence of anc ient life on the planet. A wide range of hypothesized siliciclastic and non -siliciclastic sedimentary deposits on Mars are of particular interest for the future exobiological exploration. Searching the substrate of sedimentar y deposits is the preferred strategy because it is difficult to preserve or ganic matter or geochemical evidence of biological activity in the photoche mically active and oxidizing surface environment of Mars. (C) 2000 Elsevier Science Ltd. All rights reserved.