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Exploring Mars For Evidence Of Past Or Present Life

Elizabeth Carter
NASA Ames Research Center			Oct. 17, 1997
Moffett Field, CA
650/604-2742
ecarter@mail.arc.nasa.gov

RELEASE: 97-75AR

EXPLORING MARS FOR EVIDENCE OF PAST OR PRESENT LIFE

Alternative exploration strategies designed to detect evidence of past or
present life on Mars are the subject of a presentation to be given by
NASA's Dr. Jack Farmer at the Geological Society of America (GSA)
Annual Meeting in Salt Lake City, Utah, on Oct. 20, 1997.

Farmer, an exobiologist and paleontologist at NASA's Ames Research
Center, Moffett Field, CA, asks the question, "if there was there life on
Mars, where would it be found?" The crucial first step in implementing
an exploration strategy is identifying the best places to look, he states.

"A close synergy between orbital and landed science will be essential for
effective site selection to explore for past life," Farmer said.

In exploring for a Martian fossil record, present scenarios assume that
rover missions in 2001 and 2003 will gather and cache samples for
possible return-to-Earth mission in 2005. A critical step is to locate
accessible surface outcrops of water-formed sedimentary deposits on
Mars. The effectiveness of a sample return mission in addressing the
question of past Martian life will be significantly enhanced by

1) obtaining high spatial resolution data from important sites during the
2001 orbital mission,

2) delivering highly mobile robotic platforms to exopaleontological sites
in 2001 and 2003, e.g. rovers that are capable of multiple kilometer
traverses during nominal mission times, and

3) carrying out in-situ mineralogical and geochemical analyses of a variety
of rock types as a basis for selecting samples for return to Earth.

Potentially important targets include fine-grained, clay-rich detrital
sediments, water-lain volcanic ash deposits, and chemical precipitates-
lithologies that on Earth have been shown to be especially favorable for
preserving fossil biosignatures of microbial life.

According to Farmer, exploring for Martian life will require a fundamentally
different approach than exploring for a fossil record. A deep subsurface
hydrosphere, touted as the most likely haven for an extant biota on Mars
may yet exist beneath the Martian cryosphere at a depth of several
kilometers. However, during the Mars Global Surveyor (MGS) Program,
robotic platforms will be unable to penetrate deeper than a few meters.

Farmer believes that the technological challenge of deep subsurface drilling
presently provides the most compelling scientific reason for mounting human
missions to Mars. But as a first step in planning drilling missions, systematic
orbital searches using high spatial resolution multispectral imaging should
be undertaken sometime during the MGS Program (perhaps in 2003) to
identify spatially-restricted thermal anomalies, and concentrations of water,
methane or other reduced gases that may indicate the presence of near
surface hydrothermal systems.