posted on Jun, 18 2004 @ 12:26 PM
ALIEN LIFEFORMS MAY BE INSIDE
By Steve Farrar, Science Correspondent
Life forms so alien that scientists may simply not have recognised
evidence of their existence could inhabit the Earth, according to
a leading scientist.
Dr Tom Gold, emeritus professor of astronomy at Cornell University
in America, believes that organisms based on silicon - completely
unrelated to all the carbon-based life man has encountered so far
- may live at great depths.
In a forthcoming book he will suggest that scientists should take
the possibility more seriously. Gold, who is a member of the Royal
Society, previously predicted that vast amounts of more conventional
bacteria live miles down within the Earth's crust. Scientists initially
dismissed the idea, but many now agree with him.
"So long as nobody suspects there could be silicon-based life,
we may just not be clever enough to identify it," he said last week.
Rocks bearing signs of silicon-based organisms may already be
sitting in laboratories, he believes, with their significance overlooked.
Every known living organism, from bacteria to mankind, is based
on the chemistry of carbon, which forms the complex molecules such
as DNA that are central to our existence. Scientists believe that
if extraterrestrial life is found, the chances are that it, too,
will be carbon-based.
Silicon has many chemical similarities to carbon, prompting scholars
and science fiction writers to dream up new life forms. Huge "space
slugs" that can swallow space ships appear in the film The Empire
Strikes Back; in an episode of Star Trek a rock-like
alien attacked Captain Kirk's crew; and killer parasites based on
silicon surfaced in The X-Files when scientists explored
the interior of a volcano.
Gold's life forms, if they exist, would most likely be micro-organisms
capable of withstanding enormous pressures and temperatures, living
in tiny pores inside rock deep within the Earth's crust. They could
draw energy from dissolved gases and surrounding minerals.
Gold's ideas, which centre on an alternative explanation for oil
and mineral deposits, will be published in his book, The Deep Hot
Biosphere, in January.
"It is speculative but logical that there could be a large bio-chemical
system very deep down which works better at high temperatures and
pressures," he said.
Others are sceptical. Dr Harold Klein, who headed the Viking lander
project team that searched for signs of life on Mars in the 1970s,
pointed out that silicon was far inferior to carbon at forming the
complex polymers crucial for life.
"I personally doubt the idea of silicon-based life. If we do find
organisms far down inside the Earth, I'd bet they'd be carbon-based,"
Nevertheless, he urges future missions to Mars to carry an instrument
to test for non-carbon-based organisms - just in case. It is possible
that the chemistry of silicon is altered sufficiently by the great
temperatures and pressures deep in the Earth to make it more suited
to forming complex molecules, according to David Noever, a research
scientist at Nasa's new Astrobiology Institute.
He said some scientists at the American space agency were treating
the idea of silicon-based organisms seriously, particularly with
a view to searching for extraterrestrial life.
"It's almost naive to assume all life must be carbon-based; I
could possibly make good cases for life based on both silicon and
phosphorus," he said.
Silicon is used by some carbon-based single-cell organisms called
diatoms to form protective shells, according to Dr David Williams,
a diatom researcher at the Natural History Museum in London. But
diatoms are still fundamentally carbon-based.
However, bizarre organisms have been found in recent years deep
in the Earth's crust. Steve Jones, professor of genetics at University
College London, said: "There's an unknown universe down there that
has already produced organisms with metabolisms so strange that,
by comparison, man and mushrooms are almost identical, so God knows
what else they'll find."
Microbes have been found living on the ocean floor at depths and
temperatures where life was previously thought unsustainable.
Without knowing what silicon-based life forms might be like, said
Dr Harry Elderfield, an earth scientist at Cambridge University,
it is almost impossible to predict how scientists could even test
Yet Gold has been described by Stephen Jay Gould, president of
the American Association for the Advancement of Science, as one
of the most iconoclastic scientists - but one who is often right.
This information comes from the 22 November,
1998 issue of The Sunday Times.
(reprinted with permission)