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While Martian soil contains no organic matter, conditions beneath the surface may once have been more favorable to the existence of life on the Red Planet, said three NASA Jet Propulsion Laboratory scientists.
Seeds planted in lunar soil readily germinate when given water and nutrients, but Martian soil shows no signs of biological activity when similarly treated.
The entire Martian surface is apparently sterile at present due to process called photocatalytic oxidation, the destruction of any organic molecules by free oxygen radicals.
Dr. Kevin Pang, in paper prepared for presentation before Dec. 6 session of the 1989 Fall Meeting of the American Geophysical Union at San Francisco, said organic compounds were recently discovered deep in the interior of meteorite believed to have come from Mars.
Pang's co-authors are Dr. Fun-Dow Tsay and Brian O. Franklin.
That meteorite, known as EETA 79001, contained carbonaceous material, and that indicates, the scientists said, that the subsoil of Mars may be more benign to life forms than its surface.
In times past, about three times as many meteorites hit Mars as hit the moon.
Assuming the same fraction of carbonaceous chondritic meteorites striking both bodies, Martian soil should have been organically richer than lunar soil at one time.
The fertility of Martian soil would have been further enhanced by moons that, over time, fell to the surface of Mars, Pang said. The science team based its conclusions on evidence that Mars' two satellites, Phobos and Deimos, have compositions similar to carbonaceous chondrites, rich in organic compounds, and that in past times Mars was surrounded by swarm of similar satellites which eventually crashed into the planet.
"Since more than 99 percent of the ancient satellite mass impacted prior to the last episode of Martian volcanism (about 1.1 billion years ago)," they said, "it appears that there was time when an organically rich soil, thick atmosphere and running water coexisted on Mars."
The fastest way to get life started under such favorable conditions is by panspermia, Pang said.
Panspermia is theory that life exists throughout the universe and develops where an environment permits. "If life had originated on Mars by panspermia the most likely source of spores is the Earth," the scientists said.
"The presence of moon and Mars rocks on Earth forces us to conclude that there must be Earth rocks on Mars," they said, and such rocks could have carried primitive life to the Red Planet.
Impact and trajectory analyses by Dr. Jay Melosh of the Lunar and Planetary Institute in Houston, Texas, are consistent with this conclusion, they said. If there are fossils of life onMars, they may be like those on Earth, they said.
Their paper, entitled, "Paleoatmosphere, Lost Satellites, Panspermia and the Possible Development of Life on Early Mars," resulted from NASA-funded study at JPL in Pasadena, Calif.