Endeligt bevist? ER vi marsmænd og kvinder?
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http://www.guardian.co.uk/uk_news/story/0,,1989431,00.html
Microbe experiment suggests we could all be Martians
Ian Sample, science correspondent
Saturday January 13, 2007
The Guardian
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."