[meteorite-list] Can Microbes Survive a Million-Year Space Journey? Experts Say Yes

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 16 Sep 2009 09:01:52 -0700 (PDT)
Message-ID: <200909161601.n8GG1qqL001175_at_zagami.jpl.nasa.gov>

http://zikkir.com/scitech/691

Can Microbes Survive a Million-Year Space Journey? Experts Say Yes
By Jason McManus
16 September 2009

In a unique experiment on a galactic scale, millions of bacterial spores
have been purposely exposed to space, to see how solar radiation affects
them and the results supported the idea that not only could life have
arrived on Earth on meteorites, but that considerable material has
flowed between planets.

Closer to home, scientists have analyzed aerial dust samples collected
by Charles Darwin and confirmed that microbes can travel across
continents without the need for planes or trains - rather bacteria and
fungi hitch-hike by attaching to dust particles. Their results clearly
show that diverse microbes, including ascomycetes, and eubacteria can
live for centuries and survive intercontinental travel.

In a paper published in Environmental Microbiology, Dr. Anna Gorbushina
(Carl-von-Ossietzky University, Oldenburg, Germany), Professor William
Broughton (University of Geneva, Switzerland) and their colleagues
analyzed dust samples collected by Charles Darwin and others almost 200
years ago.

Recent space-centric studies have shown that some rock-inhabiting
organisms, known as "endoliths," might be able to survive a trip through
space and a plunge through a planet???s atmosphere to the surface.
However, nobody knew whether these organisms could survive the initial
trip into space.

Recently, an international team of researchers, led by Gerda Horneck of
the Institute of Aerospace Medicine in Cologne, Germany, selected a
number of hardy microbes from Earth and tested their ability to
hitchhike aboard rocks similar to Martian meteorites.

The organisms used in the study included bacterial endospores,
endolithic cyanobacteria and lichens. This selection provided a wider
range of organisms than in other studies performed to date, including
not just simple bacteria but also more complex eukaryotic organisms.

The researchers looked at previous studies of Martian meteorites that
provided information about the kinds of forces needed to eject rocks
from a large planet. Using this data, the researchers developed a series
of tests designed to simulate these pressures on the selected organisms.

By smashing the life-containing rocks between metal plates, the
researchers were able to determine which organisms are capable of
surviving different pressures caused by asteroid impacts and ejection
into space. Ultimately, they discovered that a wide range of organisms
would be capable of surviving impacts on or Earth.

"Our results enlarge the number of potential organisms that might be
able to reseed a planetary surface after early very large impact events,
and suggest that such a re-seeding scenario on a planetary surface is
possible with diverse organisms," the researchers report.

In earlier experiments, Horneck and her colleagues used the Russian
Foton satellite to expose 50 million unprotected spores of the bacterium
Bacillus Subtilis outside the satellite. UV radiation from the Sun
killed nearly all of the spores, and did so even when the spores were
confined under quartz.

To test if meteorites might protect bacteria on their journey through
space, Horneck and her colleagues mixed samples of 50 million spores
with particles of clay, red sandstone, Martian meteorite, or simulated
Martian soil and made small lumps a centimeter in diameter. Between
10,000 and 100,000 spores of the original 50 million survived and when
mixed with red sandstone, nearly all survived, suggesting that even
meteorites a centimeter in diameter can carry life from one planet to
another, if they completed the journey within a few years. In a rock a
meter across, bacteria could probably survive for millions of years.

In a separate experiment, another team ran computer models of giant
impacts like Chicxulub. In the simulations, millions of large boulders
were ejected from the earth. About 30 boulders from each Earth impact
even reached Titan, and they entered Tita's atmosphere slower than most
meteors hit Earth's atmosphere. Big rocks from Earth have no doubt
reached Enceladus, as well.

"That kind of entry should be no problem," agreed Allan Treiman of the
Lunar and Planetary Institute in Houston, quoted in New Scientist.
Bacteria were found in wreckage of the shuttle Columbia when it
re-entered Earth's atmosphere in 2003. And Earthly lichen survived when
exposed to the harsh environment of space.

The research is detailed in the Spring 2008 issue of the journal
Astrobiology.
Received on Wed 16 Sep 2009 12:01:52 PM PDT