[meteorite-list] Bacteria Could Survive in Martian Soil

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 2 Nov 2009 14:39:18 -0800 (PST)
Message-ID: <200911022239.nA2MdIhg010507_at_zagami.jpl.nasa.gov>

http://www.universetoday.com/2009/10/30/bacteria-could-survive-in-martian-soil/

Bacteria Could Survive in Martian Soil
Written by Nicholos Wethington
Universe Today
October 30, 2009

Multiple missions have been sent to Mars with the hopes of testing the
surface of the planet for life - or the conditions that could create
life - on the Red Planet. The question of whether life in the form of
bacteria (or something even more exotic!) exists on Mars is hotly debated,
and still requires a resolute yes or no. Experiments done right here on Earth
that simulate the conditions on Mars and their effects on terrestrial
bacteria show that it is entirely possible for certain strains of bacteria
to weather the harsh environment of Mars.

A team led by Giuseppe Galletta of the Department of Astronomy at the
University of Padova simulated the conditions present on Mars, and then
introduced several strains of bacteria into the simulator to record
their survival rate. The simulator - named LISA (Laboratorio Italiano
Simulazione Ambienti - reproduced surface conditions on Mars, with
temperatures ranging from +23 to -80 degrees Celsius (73 to -112 Fahrenheit),
a 95% CO2 atmosphere at low pressures of 6 to 9 millibars, and very strong
ultraviolet radiation. The results - some of the strains of bacteria were
shown to survive up to 28 hours under these conditions, an amazing feat
given that there is nowhere on the surface of the Earth where the temperatures
get this low or the ultraviolet radiation is as strong as on Mars.

Two of the strains of bacteria tested - Bacillus pumilus and Bacillus
Nealsonii - are both commonly used in laboratory tests of extreme
environmental factors and their effects on bacteria because of their
ability to produce endospores when stressed. Endospores
are internal structures of the bacteria that encapsulate the DNA and
part of the cytoplasm in a thick wall, to prevent the DNA from being
damaged.

Galletta's team found that the vegetative cells of the bacteria died
after only a few minutes, due to the low water content and high UV
radiation. The endospores, however, were able to survive between 4 and
28 hours, even when exposed directly to the UV light. The researchers
simulated the dusty surface of Mars by blowing volcanic ash or
dust of red iron oxide on the samples. When covered with the dust, the
samples showed an even higher percentage of survival, meaning that it's
possible for a hardy bacterial strain to survive underneath the surface
of the soil for very long periods of time. The deeper underneath the
soil an organism is, the more hospitable the conditions become; water
content increases, and the UV radiation is absorbed from the soil above.

Given these findings, and all of the rich data that came in last year
from the Phoenix lander - especially the discovery of perchlorates -
continuing the search for life on Mars still seems a plausible endeavor.

Though this surely isn't a confirmation of life on Mars, it shows that
even life that isn't adapted to the conditions of the planet could
potentially hold out against the extreme nature of the environment
there, and bodes well for the possibility of Martian bacterial life
forms. The LISA simulations also indicate the importance of avoiding
cross-contamination of bacteria from Earth to Mars
on any scientific missions that travel to the planet. In other words,
when we finally are able to definitively test for life on our
neighboring planet, we don't want to find out that our Earth bacteria
have killed off all the native lifeforms!

Sources: Arxiv papers:
http://lanl.arxiv.org/abs/0910.4830
http://lanl.arxiv.org/abs/0706.0530
Received on Mon 02 Nov 2009 05:39:18 PM PST