[meteorite-list] Microbe Experiment Suggests We Could All Be Martians

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Sun, 14 Jan 2007 19:18:37 -0800 (PST)
Message-ID: <200701150318.TAA12670_at_zagami.jpl.nasa.gov>

http://www.guardian.co.uk/space/article/0,,1989474,00.html

Microbe experiment suggests we could all be Martians
Ian Sample
The Guardian (United Kingdom)
January 13, 2007

Life on Earth may have announced its arrival billions of years ago with
a whistle and a thump, according to planetary scientists.

Experiments by an international team of researchers back a controversial
theory that life flourished on Earth after primitive organisms arrived
aboard a meteorite, itself gouged from Mars by a giant impact.

The theory supposes that life was able to gain a tentative foothold on
the red planet as it cooled down and became more hospitable several
billion years ago. At the time, the planet's surface was regularly
bombarded with rocky detritus from the asteroid belt, knocking clumps of
rock and the microbes living on them into space, where the gravity of
the sun brought them hurtling towards Earth.

Charles Cockell, at the Open University, who studies microbes in extreme
environments, joined a team of German and Russian scientists to test
whether microbes could survive the enormous shock of being blasted into
space and crash landing on another planet.

They gathered colonies of micro-organisms including cyanobacteria, which
live in rocky fissures, lichen, which smother their surfaces, and spores
of the hardy bacterium Bacillus subtilis, and sandwiched them between
slices of gabbro, a coarse-grained rock similar to that known to make up
Martian meteorites.

The researchers then used high explosives to fire a steel plate at the
sandwiched organisms and after each shot transferred the microbes to a
dish to see if any had survived. The shocks were equivalent to those
suffered by Martian meteorites that have been found on Earth, with
pressures of up to 50 billion pascals. One pascal is equivalent to the
pressure exerted by a ?5 note resting on a surface. The pressure in a
car tyre is equivalent to 200,000 pascals.

To their surprise, the scientists found the lichen and bacterial spores
survived all but the most cataclysmic impacts up to 45 billion pascals.
The cyanobacteria survived shocks of up to 10 billion pascals.

The findings support the theory of "lithopanspermia", which suggests
life may be spread from one planet to another aboard lumps of rock that
are knocked off the surface.

Writing in the journal Icarus, the scientists state: "These results
strongly confirm the possibility of a 'direct transfer' scenario of
'lithopanspermia' for the route from Mars to Earth, or from any
Mars-like planet to other habitable planets in the same stellar system."
Received on Sun 14 Jan 2007 10:18:37 PM PST