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SCIENCE : ASTRONOMY
The Space Invaders
An Indo-British team discovers startling proof of
how comets may have sowed the seeds of life on earth. If true, it could
lead to profound changes in our understanding of the origins of species.
By Raj Chengappa
Comets, those fuzzy,
luminous, tadpole-shaped objects that occasionally blaze across the skies,
have always inspired awe. The ancients saw them as harbingers of bizarre
events, even major disasters. The a.d. 1456 appearance of Halley's Comet
was blamed for earthquakes, diseases, a mysterious red rain and even the
birth of a two-headed animal. Only in more recent times have scientists
been able to strip away much of the mystique surrounding these "dirty
snowballs" periodically circling the solar system.
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CLOUDS OF LIFE: The first photographs of viable living cells that
the Indo-British team found in samples collected from stratosphere
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Now, in a discovery that could significantly
alter our understanding of how life began on earth, the ancient's fear
of the comets may well have been justified. Last week, at a science conference
of astro-biologists at San Diego, USA, a team of Indian and British researchers
presented what was the first real evidence of the presence of living organisms
floating in the earth's stratosphere. Using a special upper atmosphere
balloon probe built by the Indian Space Research Organisation (ISRO),
the team's analysis of air samples taken at heights between 25 km and
41 km in Hyderabad were startling. It showed a profusion of bacteria-like
organisms swarming in a region where the temperature is as cold as in
Antarctica and the atmosphere so rarefied that terrestrial life is almost
non-existent.
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WHAT
THEY FOUND
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Clumps of living cells at heights of 25-41 km in the sky that point
to an extra-terrestrial origin.
These cells bombard the earth every day in incredibly large numbers.
They are first proof that life may not have originated on earth
as widely believed, but came from deep space.
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Chandra Wickramasinghe, professor at the Centre
for Astrobiology, Cardiff University, UK, and a key member of the Indo-British
scientific team, says: "Our findings have a profound impact on the
concept of how life began on earth. It is clear that this invasion from
space has had a lot more to do with it." If the team's findings are
validated by further experiments, it would provide strong evidence that
life was first created in deep space and not on the earth itself as is
widely believed. Acting as super sperm distributors of the cosmos, comets
passing through the earth's vicinity may have deposited genetically rich
cosmic dust on the planet. These are believed to have sowed the seeds
of primitive life on earth.
The alternative theory that has so far held
sway is that life on earth had evolved from a primordial chemical soup
some four billion years ago. The planet was then just being formed. The
solar system itself was developing. The young sun shone with only a third
of its present power. The atmosphere had no free oxygen. Volcanoes erupted
on earth with tremendous frequency and meteorite showers rained down as
if a machine gun was spraying them from space. In this primeval atmosphere,
a cataclysmic chain of chemical events occurred possibly in the depths
of the ocean that saw the formation of protein molecules-the basic building
blocks of all life.
First propounded by Russian scientist A.I. Oparin
in 1924, the cosmic soup theory was only partially validated by a chance
laboratory experiment, that too 30 years later. In 1954, Stanley Miller,
a graduate student in the University of Chicago, passed a high-voltage
electric current in a mixture of gases similar to what may have been present
in early earth. To his astonishment he found that amino acids, essential
to support life forms, had formed at the bottom of his reactor vessel.
Since then theoreticians have worked out the
broad outline of how life evolved. After the prebiotic phase for the next
three billion years, all organisms were essentially single-celled amoeba-
like creatures. Multicellular organisms appeared only after that. Only
500 million years ago did the explosion of species occur. Human beings
appeared only 100 thousand years ago-a blink in earth's existence. It
also fitted in neatly with Charles Darwin's theory of 1858 of how only
the fittest of the species survived as the complexity of life grew.
There are, however, gaping holes in the chemical
evolution theory. Indian astronomer Jayant Narlikar, a member of the joint
Indo-British research team, points out that the probability of a chain
of molecules assembling into exquisitely precise DNA units to create life
is almost zero. It has the same chance as that of a monkey hammering out
a full page of coherent sentences while playing with a typewriter. There
is also some evidence to show that the existence of life now predates
the earth's formation leaving the cosmic soup supporters sputtering for
an explanation.
Wickramasinghe, along with the famed astronomer
Sir Fred Hoyle, then tried to turn the whole argument on its head. In
1974, they propounded that rudimentary life evolved in deep space itself.
The "brush of the tail of a comet" rich in such genetic material
brought life to earth. Wickramasinghe recollects ruefully: "Our theory
was considered wildly outrageous." And they were laughed out of scientific
conferences. Only a laboratory demonstration could give their theory credence.
The possibility of collecting such evidence
was extremely slim. The first effort to collect bacteria from atmosphere
was made in the 1960s when the US space agency NASA sent a few probes.
But it failed because the NASA team could not prove that the evidence
they collected was free from contamination from the earth's atmosphere.
In 1980, Hoyle and Wickramasinghe approached the British Aerospace Agency.
Hoyle's wisecrack that "space is just an hour's drive away if your
car could go straight upwards" didn't cut much ice with the officials.
They told him that his experiment was not worth pursuing.
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