[meteorite-list] Viking Mission Results Indicates Presence of Life on Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 8 Jan 2007 09:15:22 -0800 (PST)
Message-ID: <200701081715.JAA20437_at_zagami.jpl.nasa.gov>

http://www.ccnmag.com/news.php?id=4702

Viking Mission Results Indicates Presence of Life on Mars
CCNews
January 7, 2007

We may already have "met" Martian organisms, according to a paper
presented Sunday (Jan. 7) at the meeting of the American Astronomical
Society in Seattle.

Dirk Schulze-Makuch of Washington State University and Joop Houtkooper
of Justus-Liebig-University, Giessen, Germany, argue that even as new
missions to Mars seek evidence that the planet might once have supported
life, we already have data showing that life exists there now - data from
experiments done by the Viking Mars landers in the late 1970s.

"I think the Viking results have been a little bit neglected in the last
10 years or more," said Schulze-Makuch. "But actually, we got a lot of
data there." He said recent findings about Earth organisms that live in
extreme environments and improvements in our understanding of conditions
on Mars give astrobiologists new ways of looking at the 30-year-old data.

The researchers hypothesize that Mars is home to microbe-like organisms
that use a mixture of water and hydrogen peroxide as their internal
fluid. Such a mixture would provide at least three clear benefits to
organisms in the cold, dry Martian environment, said Schulze-Makuch. Its
freezing point is as low as -56.5 degrees C (depending on the
concentration of H2O2); below that temperature it becomes firm but
does not form cell-destroying crystals, as water ice does; and H2O2 is
hygroscopic, which means it attracts water vapor from the atmosphere -
a valuable trait on a planet where liquid water is rare.

Schulze-Makuch said that despite hydrogen peroxide's reputation as a
powerful disinfectant, the fluid is also compatible with biological
processes if it is accompanied by stabilizing compounds that protect
cells from its harmful effects. It performs useful functions inside
cells of many terrestrial organisms, including mammals. Some soil
microbes tolerate high levels of H2O2 in their surroundings, and the
species Acetobacter peroxidans uses hydrogen peroxide in its metabolism.

Possibly the most vivid use of hydrogen peroxide by an Earth organism is
performed by the bombardier beetle (Brachinus), which produces a
solution of 25 percent hydrogen peroxide in water as a defensive spray.
The noxious liquid shoots from a special chamber at the beetle's rear
end when the beetle is threatened.

He said scientists working on the Viking projects weren't looking for
organisms that rely on hydrogen peroxide, because at the time nobody was
aware that such organisms could exist. The study of extremophiles,
organisms that thrive in conditions of extreme temperatures or chemical
environments, has just taken off since the 90s, well after the Viking
experiments were conducted.

The researchers argue that hydrogen peroxide-containing organisms could
have produced almost all of the results observed in the Viking experiments.

o Hydrogen peroxide is a powerful oxidant. When released from dying
cells, it would sharply lower the amount of organic material in their
surroundings. This would help explain why Viking's gas
chromatograph-mass spectrometer detected no organic compounds on the
surface of Mars. This result has also been questioned recently by Rafael
Navarro-Gonzalez of the University of Mexico, who reported that similar
instruments and methodology are unable to detect organic compounds in
places on Earth, such as Antarctic dry valleys, where we know soil
microorganisms exist.

o The Labeled Release experiment, in which samples
of Martian soil (and putative soil organisms) were exposed to water and
a nutrient source including radiolabeled carbon, showed rapid production
of radiolabeled CO2 which then leveled off. Schulze-Makuch said the
initial increase could have been due to metabolism by hydrogen
peroxide-containing organisms, and the leveling off could have been due
to the organisms dying from exposure to the experimental conditions. He
said that point has been argued for years by Gilbert Levin, who was a
primary investigator on the original Viking team. The new hypothesis
explains why the experimental conditions would have been fatal: microbes
using a water-hydrogen peroxide mixture would either "drown" or burst
due to water absorption, if suddenly exposed to liquid water.

o The possibility that the tests killed the organisms they were looking
for is also consistent with the results of the Pyrolytic Release
experiment, in which radiolabeled CO2 was converted to organic
compounds by samples of Martian soil. Of the seven tests done, three
showed significant production of organic substances and one showed much
higher production. The variation could simply be due to patchy
distribution of microbes, said Schulze-Makuch. Perhaps most
interesting was that the sample with the lowest production?lower
even than the control - had been treated with liquid water.

The researchers acknowledge that their hypothesis requires further
exploration. "We can be absolutely wrong, and there might not be
organisms like that at all," said Schulze-Makuch. "But it's a consistent
explanation that would explain the Viking results."

He said the Phoenix mission to Mars, which is scheduled for launch in
August, 2007, offers a good chance to further explore their hypothesis.
Although the mission's experiments were not designed with
peroxide-containing organisms in mind, Phoenix will land in a sub-polar
area, whose low temperatures and relatively high atmospheric water
vapor (from the nearby polar ice caps) should provide better growing
conditions for such microbes than the more "tropical" region visited by
Viking. Schulze-Makuch said the tests planned for the mission,
including the use of two microscopes to examine samples at high
magnification, could reveal whether we had the answer all along - and
if we've already introduced ourselves to our Martian neighbors in a
harsher way than we intended.

"If the hypothesis is true, it would mean that we killed the Martian
microbes during our first extraterrestrial contact, by drowning - due to
ignorance," said Schulze-Makuch.
Received on Mon 08 Jan 2007 12:15:22 PM PST