[meteorite-list] Formaldehyde Claim Inflames Martian Life Debate

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Feb 25 16:41:01 2005
Message-ID: <200502252140.j1PLehx11986_at_zagami.jpl.nasa.gov>

http://www.nature.com/news/2005/050221/full/050221-15.html

Formaldehyde claim inflames martian debate
Mark Peplow
nature.com
February 25, 2005

Top scientist defends data that he says point strongly to life on Mars.

Formaldehyde has been found in the martian atmosphere, according to a
senior scientist working with the Mars Express orbiter. If correct, the
discovery provides strong evidence that Mars is either extremely
geologically active, or harbouring colonies of microbial life. But many
experts are not yet convinced.

The claim comes from Vittorio Formisano, who is in charge of the
Planetary Fourier Spectrometer on the European Space Agency's orbiter.
The spectrometer analyses infrared light, whose frequencies carry the
fingerprints of chemicals in the atmosphere.

The most likely source of formaldehyde (CH2O) is the oxidation of
methane (CH4), which has already been identified in the martian skies.
So the presence of formaldehyde itself is not too surprising, says Michael
Mumma, of NASA's Goddard Space Flight Centre near Washington DC, who
studies the martian atmosphere. Any oxidizing atmosphere such as Mars's
that contains methane should also have formaldehyde, he explains.

Big claim

The truly eye-opening part is the sheer quantity of formaldehyde that
Formisano claims to have found: about 10 to 20 times more than there is
of methane. This means that estimates of martian methane production must
be revised upwards substantially, as most of the gas is oxidized as soon
as it comes out of the ground, he says.

"If you consider formaldehyde as oxidized methane, then Mars is
producing 2.5 million tonnes of methane a year," says Formisano.

This is simply too much to be accounted for by any known geological
process, he says, so some other source (possibly life) must be involved.
However, other planetary scientists say the planet alone could still be
responsible.

"We don't know the intricacies of [martian] geochemistry," says Rocco
Mancinelli, an astrobiologist from NASA's Ames Research Center in
Moffett Field, California.

Formisano presented his results to a packed session of the Mars Express
Science Conference at Noordwijk in the Netherlands on 24 February.

Unstable hope

The discovery of martian methane last year excited scientists, who said
that there were two likely sources of the gas: active geological
processes beneath the planet's surface or a population of
methane-generating microbes. Because Mars was long thought to be a dead
planet, devoid of both life and geothermal activity, either prospect
came as a revelation.

However, a molecule of methane can typically survive for about 350 years
in the atmosphere before being broken down by the Sun's ultraviolet
radiation. So the possibility remained that the gas could have been
delivered to the planet by a colliding comet, or by an occasional
release from an underground reservoir.

Formaldehyde is far more unstable, surviving for just 7.5 hours or so
before breaking apart. The majority of scientists agree that methane is
the most likely precursor for formaldehyde on Mars, so this means that
the planet's production of methane must be an ongoing, continuous
process, says Formisano.

Going sceptic

Formisano is careful to point out that he has not proved there is life
on Mars. "I do believe there is life inside the planet, maybe 50 to 100
metres below the surface, but there is a long way to go to demonstrate
that."

"We all want to believe in something," says Yuk Yung, a planetary
geologist from the California Institute of Technology, Pasadena. "Even
as scientists we're not completely objective, especially about something
we've worked on for ten years. There's enormous pressure to deliver, and
under this pressure you can easily believe things that are unbelievable."

Many scientists are sceptical about the quality of Formisano's data.
"The measurements are right on the borderline of the [instrument's
ability]," says Mancinelli.

"I don't believe it," adds Yung. He explains that Formisano's infrared
fingerprint of the formaldehyde in Mars's skies should match a
laboratory sample of the gas, "and the match is just not convincing".

But Formisano argues that his martian spectrum tallies in 15 key places,
which should be enough to convince anyone: "It's not a matter of opinion
any more," he says. He adds that, since he presented his data at the
conference, several sceptics have already changed their views. He points
out that although rejected by Nature, the research will soon be
published in the journal Planetary and Space Science.

Acid test

Formisano also announced at the conference that he has found traces of
hydrogen fluoride (HF) and hydrogen bromide (HBr) in the atmosphere,
which are probably produced when acids break down certain minerals in
the soil.

Many scientists believe that Mars once had briny, acidic seas
that may have been conducive to life. "An acidic environment
still exists," says Formisano. "On Earth, there are certain
bacteria that prefer very acid conditions."

He also points out that he has found higher concentrations of methane
directly above an area of Mars that seems to be covered in pack ice.
This raises the tantalizing possibility of a microbial colony living beneath
the surface.

Mumma says that more convincing evidence for life is needed. Continuous
production of heavier hydrocarbons such as propane, which cannot come
from geothermal processes, would be a key finding, he says. Better still
would be a skew in the ratio of carbon isotopes in the air, as produced
by organisms on Earth.

NASA and the European Space Agency are both planning Mars missions for
the end of the decade that will look for precisely that.
Received on Fri 25 Feb 2005 04:40:43 PM PST