Search for Life on Mars 

Dr. Michael J. Mumma (Goddard Center for Astrobiology, Solar System Exploration Division, NASA Goddard Space Flight Center)

Abstract
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For centuries, the planet Mars has been regarded as a possible abode for
life.  Serious searches for the signatures of life began with the 19th
century work of Percival Lowell, and continue today with both telescopic
investigations and landed missions.  While early work focused on
phenomenology and bordered on fantasy, modern scientific inquiry has
emphasized the search for biomarker gases on Mars, and the search for
chemical signatures of life in the soil and rocks at the planet's surface.

Living systems produce more than 90% of Earth's atmospheric methane; the
balance is of geochemical origin. The discovery of methane on Mars will be
described, along with the ongoing extended search for clues to its origins.  
The possible origins of Mars methane will be discussed in the context of
terrestrial analogue sites where geologic and biologic methane production
now occurs - ranging from sub-permafrost zones in the arctic to
hydrothermal vents in the deep ocean. I will briefly touch upon experiments
conducted by landed spacecraft, ranging from the Viking Life Science
Experiments in 1976 to the impending Mars Science laboratory, and the Trace
Gas Orbiter and ExoMars missions now being developed for flight in the
coming decade.  In this lecture, I will present a balanced view of the
search for life on Mars.