DID WE FIND MARTIAN LIFE 20 YEARS AGO?
2 Nov 1996
Source: Nando Times
LONDON (Nov 12, 1996 01:01 a.m. EST) -- Life was discovered on Mars 20 years
ago, and further evidence is awaiting a new generation of space missions.
This is the startling claim of an American scientist intimately involved
with a NASA mission which declared the Red Planet sterile 20 years ago.
Dr. Gilbert Levin was one of the principal scientists involved in the Viking
mission in 1976. He conducted a key experiment to look for life -- and, he
believes, found it.
But, to his dismay, the official consensus that emerged was that Mars had
never harbored life. "A number of explanations have been proposed to explain
the results of my experiment," Levin, 72, declares. "None of them are
convincing. I believe that Mars has life today."
His certainty comes from this year's discovery of what appear to be
fossilised microbes in Martian meteorites, hunks of rock which had been
flung out of the crust of Mars in the ancient past. And it's hardly
surprising. "Life is hardier than we had ever imagined," he says. "Microbes
have been found inside nuclear fuel rods inside reactors and in the depths
of the ocean where there is no light."
Mars is back on the scientific agenda. The U.S. and Russia are sending a
small flotilla of spacecraft to the Red Planet. Last Thursday NASA's Mars
Global Surveyor was successfully launched from Cape Canaveral. Next weekend,
Russia's Mars '96 will blast off from Kazakhstan. Both will reach the planet
next September. In early December, NASA's Pathfinder mission will make a
fast track to Mars and -- with impeccable timing -- arrive on Independence
Day.
Dr. Levin began his career as a sanitation engineer in California and
developed a technique to detect bacteria. Known as the labelled release
experiment, he fed a sample of water with a "broth" of radioactive lactose
and measured the carbon dioxide produced. Few companies were interested.
Then, at a cocktail party in 1959, he met T. Keith Glennan, then the first
head of NASA. "It suddenly struck me that my technique could be adapted and
flown to the Red Planet to search for life," Levin says. Glennan told Levin
to talk to Nasa's top biologist. Soon, Levin found himself on the Viking
biology team.
Earlier forays by the family of Mariner spacecraft showed that Mars was
colder, drier and more hostile than had been originally thought. But there
was still the chance that microbes lay in the soil. This was how the Viking
mission was born.
The Viking spacecraft touched down in 1976, Viking 1 on July 20 and Viking 2
on September 4. A robot arm grabbed soil samples which were fed into a
hopper, and then three experiments tried to find signs of metabolism. Dr.
Levin's experiment gave a strong signal that there were microbes in the
soil, but the other two experiments yielded less certain results. Levin
wanted to run a check.
But there were personalities involved. The Viking biology team was openly at
war. Indeed, their mutual hostility was featured in two consecutive issues
of the New Yorker magazine in 1979.
Levin found things difficult. "It was an uphill struggle for me, because I
had gone from being an engineer from a small company, to working with Nobel
laureates,' he says. "It had always been proposed that we would work on each
other's experiments but we never did." One of the team had already said that
he felt that his experiment was compromised by the others.
The supposed clincher that there were no microbes on Mars came from another
experiment. The Viking's mass spectrometer found no evidence for organic
molecules, long chains based on carbon which form the biochemical backbone
of life.
The theory explaining the absence of organic molecules went like this.
Because Mars has no ozone layer, there is nothing to protect the surface
from dangerous ultraviolet radiation from the Sun. Therefore the planet's
soils are effectively bleached.
Levin remains frustrated by this notion because he believes that the
chemistry is wrong.
The theory says that hydrogen peroxide is produced in the atmosphere on Mars
and it trickles down to the surface. The problem is that measurements made
from spacecraft in orbit around Mars and the latest telescopes on Earth have
yet to find its spectral signature.
In the late Seventies, Levin made another discovery. Looking through the PhD
thesis of the student who had developed the mass spectrometer, he realised
that both that and his own experiments had analysed the same samples from
Antarctica taken as a test before the Viking mission. (Antarctica is the
most Mars-like place on our planet and an ideal place to try out life
detection experiments.)
Levin was astonished. "The mass spectrometer had tested the same Antarctic
samples which we had looked at," he says. "It had found no organics and yet
we had found living organisms."
Levin then checked on the sensitivity of each instrument. Although he could
find as few as 50 biological cells in a given sample, the mass spectrometer
would require upwards of ten million. In other words, the instrument held up
as proving there was no life on Mars was much less sensitive than his own.
"There was no conflict in the Martian data if you understand the
sensitivities," Levin says. Despite his best efforts, Levin could not
persuade the mass spectrometer team to check their instrument against his
with known samples.
And there the matter has remained. Levin is now an experimenter on an
American instrument which will be flown on the Russian Mars '96 mission. The
Mars Oxidising Experiment will shed more light on the mysteries of the
Martian soil, but it won't be capable of looking at organics.
The answer to Levin is obvious: re-fly a more sensitive version of the
labelled release experiment. Despite trying to persuade NASA's current
chief, Daniel Goldin, who has asked the scientific community for all its
help to solve the riddle of the Martian microbes, his pleas have fallen on
deaf ears.
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