- Aliens may be living among us, say two scientists, who
argue we may even carry some alien genes.
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- Australian researchers Professor Paul Davies and Dr Charles
Lineweaver outline their hypothesis in the latest issue of the journal
Astrobiology.
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- They say the aliens in question are likely to be primitive
microbes that sprang up some four billion years ago.
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- At this time the Earth was being buffeted by a hail of
meteors and giant asteroids during what's known as the Archaean bombardment.
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- Alternately, microbial life forms may have arrived on
Earth from space and unobtrusively co-existed with us.
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- Davies, of the Australian Centre for Astrobiology at
Sydney's Macquarie University, admits the theory is speculative but says
some of these microbes may have survived undetected to this day.
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- Multiple life events
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- He says statistics indicate there's a 95% chance of life
on other Earth-like planets, a figure that he extrapolates to Earth itself.
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- "I think it's a possibility [there are aliens among
us]," he says.
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- "The basic idea is that if life is easy to form
as many astrobiologists suppose, then surely it should be formed more than
once on Earth.
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- "From what we know about the early record of life
on Earth it happened pretty fast once conditions became suitable.
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- "It's fairly easy to then work out the probability
that if life began here on Earth, which is the most Earth-like planet there
is, there's about a 95% chance that it would have done it more than once,
maybe twice, three times. Who knows?"
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- Davies says the bombardment of the planet may have resulted
in a series of "stop-go" experiments, in which life arose and
was annihilated by successive bombardments.
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- But some pockets of life may have survived the bombardment,
and today may lurk far beneath the Earth's surface, or in deep ocean hydrothermal
vents, high in the atmosphere or in contaminated lakes.
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- They may even be in solar orbit or they may have colonised
Mars, Davies says.
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- They may even exist right under our noses but may be
so foreign to us that we are failing to detect them.
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- "We have the technology to look for them, we just
haven't bothered to look," he says.
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- "Alien microbes are likely to be missed or discarded
in even the most general microbial analysis."
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- They may also have properties that don't reveal them
to be living things, he says, or they could be lying around dormant, waiting
for the right conditions to spring to life.
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- "For all these reasons we could be surrounded by
living, dormant or dead alien microbes without being aware of it,"
he says.
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- Could we be part alien?
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- We may even be part alien ourselves, Davies suggests.
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- He says some early switching of genetic material may
have occurred between our ancestors and the alien life forms that may also
have called the Earth home billions of years ago.
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- "It is conceivable that remnants of alternative
biochemical systems have become incorporated in extant organisms,"
he says.
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- "We could imagine that there would have been a mingling
of different types of life.
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- "There may have been some swapping and mixing around
of components of separate genuses."
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- He says the relatively recent discovery of archaea, tiny
microbes that look like bacteria but have an entirely different genetic
makeup, suggests the "microbial world has many hidden surprises, one
of which may be alien life".
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- "Our conclusion is that alien microbes could exist
on earth today and have remained undetected by our best efforts,"
he says.
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- Why life arose so quickly
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- Australian researcher Dr Wilfred Walsh, who lectures
in extraterrestrial life at the University of New South Wales, says Davies'
theory is not impossible.
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- He says the suggestion that life formed readily, rather
than being a rare one-off fluke, helps explain the mystery of why it arose
so quickly as soon as conditions allowed.
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- "It's certainly a bit puzzling why life managed
to originate so quickly after the Earth calmed down," he says.
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- "Either it was able to form quickly on Earth or
it arrived from elsewhere. There may be life on Earth that partly originated
off the Earth together with some that originated on the Earth."
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- ©2005 ABC
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- http://abc.net.au/science/news/stories/s1343196.htm
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