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- ATLANTA (Reuters) - Astronomers
reported on Wednesday they had found a tough but peaceful pair of bacteria
that might have been able to survive the arduous trip from Mars, back when
the Red Planet could have supported life.
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- ``They are simply happy creatures,'' scientist Curt Mileikowsky
said of the two bacteria strains that were tested for road-hardiness in
a Swedish lab. ``They don't cause any disease, they are very peaceful.''
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- But were they the first visitors from Mars?
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- The bacteria -- Bacillus subtilis (wild) and Deinococcus
radiodurans R1 -- are resistant to high speeds, extreme heat and radiation.
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- These properties would be necessary to survive a voyage
by meteoroid from Mars to Earth, Mileikowsky, of the Royal Institute of
Technology in Stockholm, and others reported at a meeting of the American
Astronomical Society in Atlanta.
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- For the last half-century, most scientists believed life
on Earth originated from simple inorganic molecules that might have been
zapped by lightning or nurtured in oceans.
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- Now research in Sweden, Canada and Finland suggests another
possibility: Tiny living things -- such as these two hardy bacteria --
may have traveled between Earth, Mars, Venus and Mercury when the planetary
system was young.
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- This is given some credence by the discovery in 1997
of a meteorite in Antarctica that some believe contains traces of fossilized
life from Mars.
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- When Mars Was Warm And Wet
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- In the earliest days, 4.5 billion years or so ago, Mars
might well have been warm and wet enough to foster life. Scientists still
do not know what turned it into the cold, barren place it is now.
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- The mode of travel would have been meteoroids, big chunks
of rock blasted out of the Martian surface by a colliding comet, the astronomers
said.
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- If microscopic life was present on Mars at the point
of contact, whatever survived the blast's concussion and heat and managed
to escape Mars' gravitational pull could have been on its way to Earth
or some other planet, according to the scientists.
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- And if it also was able to resist bombardment by radiation
in space, it might have landed safely on Earth.
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- In the first 500 million years after the planets formed,
Mileikowsky said, 50 billion potentially life-carrying rocks landed on
Earth from Mars. In the last four billion years or so, only five billion
such bodies have come to Earth.
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- The traffic in the other direction was not as heavy:
10 billion possible life-carrying objects are believed to have flown from
Earth to Mars in the first 500 million years, with only one billion going
in the last four billion years.
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- The problem is to determine whether any of these bodies
did in fact carry life, and then to find out where life began if it did
not originate on Earth.
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- The astronomers believe it probably began in our solar
system, with a very slim chance that it started elsewhere. Astronomer Sun
Kwok of the University of Calgary in Canada theorized that organic molecules
may be ejected by old stars, and some of what is tossed out could land
on Earth.
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- ``Life would have had an easier time developing on Earth''
if this was the case, Kwok said at a briefing.
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