[meteorite-list] Asteroids May Have Brought Life to Earth

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue Sep 14 16:55:25 2004
Message-ID: <200409142055.NAA04504_at_zagami.jpl.nasa.gov>

http://news.scotsman.com/latest.cfm?id=3475033

Asteroids May Have Brought Life to Earth
By John von Radowitz
The Scotsman (United Kingdom)
September 9, 2004

Asteroid craters could turn out to be the cradles of life, an expert
said today.

Killer asteroids like the one believed to have wiped out the dinosaurs
may be life creators as well as forces of destruction, said Dr Charles
Cockell.

A new theory suggests that powerful impacts from asteroids or comets
could have provided the energy and conditions needed to kick-start life
on Earth.

Part of the evidence comes from an impact crater in the Arctic formed
when a kilometre-wide object smashed into the Earth 23 million years ago.

The impact would have released as much energy as 100 million atomic
blasts as large as the one that destroyed Hiroshima.

For several hundred kilometres around the site all animal life and
vegetation would have been exterminated.

Yet scientists discovered that when the dust settled the
24-kilometre-wide crater became a haven for microbial life.

The vaporisation of minerals turned rocks within the crater porous,
allowing water to percolate through them.

At the same time they became more transparent to sunlight, which
encouraged organisms that relied on photosynthesis to survive to flourish.

"What you have here is an example of how impact events can create a new
habitat for life," said Dr Cockell, from the British Antarctic Survey,
who has investigated the site.

But he told the British Association Festival of Science that the
influence of asteroids and comets on life might go much further. They
could even have been responsible for the birth of life on Earth four
billion years ago.

An asteroid hitting the Earth at between 15 and 50 kilometres per second
produced an enormous burst of energy, most of which was released as
heat, said Dr Cockell.

The temperatures of several thousand degrees centigrade were high enough
to turn simple organic compounds into the building blocks of living things.

"There's good experimental evidence to show that impact shock can result
in the formation of amino acids and other more complex biomolecules," Dr
Cockell told the conference at the University of Exeter.

"There's a growing feeling that as well as being beneficial in terms of
habitat, impact events can also improve conditions for the evolution of
life in the first place."

This could have occurred on Mars as well as the Earth, said Dr Cockell.

Almost four billion years ago Mars had a thick atmosphere, abundant
water, and possibly life.

Dr Cockell said that, unlike on Earth, four billion-year-old craters
could still be found on Mars. They might be good places to look for
signs of life, he suggested.

There are several theories to explain how life arose on Earth, including
the formation of complex organic molecules around "black smoker"
volcanic vents on the ocean floor.

"It's quite possible that black smokers would have been a place for the
origin of life as well," said Dr Cockell.

"We don't really know. But what is becoming apparent is that there are
many environments on the early Earth that seem to offer environments for
the origin and radiation of life."

"Early Earth might have been a very good place for life to have
originated in many potential environments. Maybe it did happen in many
of these environments, and only one could continue. All this is
speculation, but the impact scenario is an interesting addition to our
total understanding of the environments that are conducive to the origin
of life."
Received on Tue 14 Sep 2004 04:55:21 PM PDT