http://www.spacedaily.com/news/life-04j.html
Comets Spread Earth-Life Around Galaxy, Say Scientists
Cardiff - Feb 11, 2004
If comets hitting the Earth could cause ecological disasters, including
extinctions of species and climate change, they could also disperse
Earth-life to the most distant parts of the Galaxy.
The "splash-back" from a large comet impact could throw material containing
micro-organisms out of the planet's atmosphere, suggest scientists from
Cardiff University Centre for Astrobiology.
Although some of this outflowing material might become sterilised by heat
and radiation, they believe that a significant fraction would survive. As
the Earth and the Solar system go round the centre of the galaxy every 240
million years, this viable bacterial outflow would infect hundreds of
millions of nascent planetary systems on the way. Hence, they suggest, the
transfer of Earth life across the galaxy is inevitable.
These ideas are discussed in detail in two papers appearing in the current
issue of the Monthly Notices of the Royal Astronomical Society.
The authors of the two papers are Professor Chandra Wickramasinghe and Dr
Max Wallis, of the Cardiff Centre for Astrobiology, and Professor Bill
Napier, an astronomer at Armagh Observatory and an Honorary Professor at
Cardiff University.
Interstellar routes for transmission of micro-organisms supports the view
that life may not have originated on Earth but arrived from elsewhere,
strengthening the "panspermia theory" that Professor Wickramasinghe and the
late Sir Fred Hoyle had been developing since 1974.
It is known that boulders and other debris may be thrown from the Earth
into interplanetary space. Professor Napier finds that collisions with
interplanetary dust will quickly erode the ejected boulders to much smaller
fragments and that these tiny, life-bearing fragments may be driven out of
the solar system by the pressure of sunlight in a few years.
The solar system could, therefore, be surrounded by an expanding 'biodisc',
30 or more light years across, of dormant microbes preserved inside tiny
rock fragments. In the course of Earth history there may have been a few
dozen close encounters with star-forming nebulae, during which microbes
might be injected directly into young planetary systems.
If planets capable of sustaining life are sufficiently common in the
Galaxy, the Cardiff based scientists conclude that this mechanism could
have infected over 10,000 million of them during the lifetime of our Galaxy.
Dr Wallis and Professor Wickramasinghe have also identified another
potential delivery route. They point out that fertile Earth ejecta would,
on impact, bury themselves in the radiation-shielded surface layers of
frozen comets.
A belt of such comets, the Edgeworth-Kuiper belt, lies beyond the planetary
system. This belt gradually leaks comets into interstellar space, some of
which will eventually reach proto-planetary discs and star-forming nebulae.
There they are destroyed by collisions and erosion, releasing any trapped
micro-organisms and seeding the formative planetary systems.
_______________________________________________________
John D. Giorgis - [EMAIL PROTECTED]
"The liberty we prize is not America's gift to the world,
it is God's gift to humanity." - George W. Bush 1/29/03
_______________________________________________
http://www.mccmedia.com/mailman/listinfo/brin-l
