title: The search for life on Mars.
abstract: Mars appears to have no life on its surface today. However, the presence of fluvial features provides evidence that liquid water was once present on the martian surface. By analogy with Earth, life may have originated on Mars early in its history, possibly during the end of the late heavy bombardment. Analysis of the one meteorite from Mars which dates to this early time appears to contain evidence of this early environment and possibly life. As the climate cooled and liquid water became unavailable, life would have eventually died out. The cold deserts of Antarctica provide a glimpse of what martian ecosystems might have been like as conditions worsened. The search for fossil evidence of past life on Mars may provide the first direct indication of life beyond Earth.
authors.affiliation: Space Science Division, NASA Ames Research Center, Moffett Field, CA 94035, USA.
authors.forename: C P
authors.initials: CP
authors.lastname: McKay
mesh_terms: D002245:Carbon Dioxide; D002247:Carbon Isotopes; D002980:Climate; D018534:Earth, Planet; D017753:Ecosystem; D005580:Fossils; D019369:Life; D018535:Mars; D009584:Nitrogen; D010788:Photosynthesis; D013026:Space Flight; D013995:Time; D014867:Water
chemical_list: D002247:Carbon Isotopes; D014867:Water; D002245:Carbon Dioxide; D009584:Nitrogen