NASA Develops Plan to Search for Martian Fossils

[Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>]

Don Savage
Headquarters, Washington, D.C.       March 22, 1994
(Phone:  202/358-1547)
 
Diane Farrar
Ames Research Center, Mountain View, Calif.
(Phone:  415/604-9000)
 
 
RELEASE:  94-49
 
NASA DEVELOPS PLAN TO SEARCH FOR MARTIAN FOSSILS
 
        A scientist at NASA Ames Research Center, Mountain View, 
Calif., has developed a strategy to search for microfossils on 
the planet Mars.  His criteria are helping to guide site 
selections related to the search for evidence of past life on 
Mars during upcoming Mars missions planned for later this 
decade. 
 
        "Our focus in the search for life (exobiology) on Mars 
has shifted to the search for ancient life because of the 
formidable conditions on the martian surface," said Dr. Jack 
Farmer.  Farmer is a paleontologist and geologist at Ames. 
 
        Exobiology is the study of the origin, evolution and 
distribution of life in the universe.  Farmer calls his newly 
invented discipline exopaleontology. 
 
        Farmer, with colleagues at Arizona State University, has 
catalogued and prioritized the sites on the martian planet 
most likely to conceal well-preserved microbial fossils.  He 
bases his strategy on the principles of Precambrian 
paleontology, the study of the Earth's earliest fossil record.
 
        The Precambrian era includes more than 90 percent of 
Earth's history.  Beginning before the time of the oldest 
Earth rocks dated 3.9 billion years ago, it continues to the 
explosion of complex multicellular life of about 540 million 
years ago. 
 
        Many scientists think that ancient Mars was a much 
warmer, more volcanically active planet with a dense 
atmosphere and abundant water. 
 
        The largest volcano in the solar system is on Mars.  
Olympus Mons, probably now dormant, is three times the height 
of Mt. Everest.  River channels and lake basins carved into 
Mars' now-dusty terrain show vast amounts of water were once 
present on the planet's surface. 
 
        The channels and lake basins are concentrated in the 
oldest, most heavily cratered terrains of Mars.  These areas 
are believed to be the same age as the earliest microbial 
fossils on Earth -- about 3.5 billion years old, Farmer said. 
 
        Since microbial communities developed on Earth in less 
than a billion years, it is plausible that organisms also 
developed on an early warm and wet Mars, he said. 
 
        If life developed on Mars, it is likely to have left a 
fossil record.  According to Farmer, the best locations to 
hunt for martian fossils are where nutrient-rich water once 
bubbled to the surface as hot springs. 
 
        Farmer, with Drs. David Des Marais of Ames and Malcolm 
Walter from Australia, has studied hot spring deposits in 
Yellowstone National Park to learn how to recognize them on 
Mars.  
 
        "Where organisms coexisted with early mineralization, we 
have the potential for preserving soft-bodied microbes, 
sometimes for billions of years," he said. 
 
        "The hot water bubbling off carbon dioxide gases creates 
alkaline conditions.  This encourages minerals like silica and 
carbonate to separate out.  The precipitating minerals encase 
and bury organisms and even entire microbial mats," he said. 
 
        Silicous thermal springs are the best places to look 
because silica is relatively stable and has a long residence 
time in Earth's crust, Farmer said.  Carbonates are more 
soluble than silica, he said, but can still preserve soft-
bodied microorganisms for billions of years.  
 
        Microbes also coexist with precipitating minerals in 
evaporating lakes like Mono Lake in California, another site 
being studied by Farmer. 
 
        Spring deposits on lake bottoms often form at lower 
temperatures that do not deteriorate the organic material as 
much as a high temperature spring.  Microbes trapped in these 
deposits can be preserved for hundreds of millions of years, 
he said. 
 
        Lakes can also evaporate, leaving salt that entraps the 
cell walls and extracellular material of microbes.  However, 
salt tends to dissolve easily.  If a surface water cycle is 
active, its crustal residence time is short, Farmer said. 
 
        Farmer presented his research at the Geological Society 
Meeting of America in San Bernardino, Calif.  Farmer and his 
colleagues recently compiled a catalog that includes Mars 
exobiology sites.  NASA will publish the catalog later this 
year.
 
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