[meteorite-list] Does The Famous Martian Meteorite Really Point To Life?

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:44:43 2004
Message-ID: <200103281843.KAA04197_at_zagami.jpl.nasa.gov>

http://www.space.com/scienceastronomy/solarsystem/mars_split_010327.html

Does The Famous Martian Meteorite Really Point To Life?
By Leonard David
space.com
28 March 2001

HOUSTON, Texas -- It is fitting that the Antarctic-recovered Martian
meteorite, ALH84001, is potato-shaped. After years of argument, the "Mars
rock" continues to be just that -- a scientific hot potato.

The inside story is that the meteorite may contain evidence of ancient life
on the Red Planet. Trying to anchor that belief in a sea of skepticism
remains a daunting and challenging, but dutiful task for those making the
assertion.

But this scientific saga has taken more blasts, twists and turns than
the meteorite took to get to Earth in the first place. Without doubt, the
Carl Sagan axiom that "extraordinary claims require extraordinary proof"
serves as the foundation for an ongoing and spirited debate

The 32nd Lunar and Planetary Science Conference, held here at NASA's Johnson
Space Center (JSC) March 12-16, served up another generous helping of claim,
controversy and downright grouchiness.

Under the microscope

The argument swirling around the Mars rock centers on whether or not there
is evidence of fossil remains of Martian microbes in the meteorite. These
fossils are purported to be in the form of tiny magnetite crystals, like
those used by aqueous bacteria on Earth. The magnetite is utilized as a
compass by the bacteria to steer toward food and energy sources.
Furthermore, magnetotactic bacteria produce magnetite crystals having a
distinct size and shape. These magnetite crystals form chains within their
cells.

Kathie Thomas-Keprta, a Houston-based Lockheed Martin scientist, reported
during the conference that single magnetite crystals inside the meteorite
are similar to those formed by 'modern' magnetotactic bacteria now living on
Earth.

Thomas-Keprta and her research colleagues contend that the crystals are
interpreted as Martian magnetofossils and "constitute evidence of the oldest
life yet found."

Thomas-Keprta said that in support of her view, early Mars likely had
freestanding bodies of liquid water, both organic and inorganic carbon (e.g.
atmospheric carbon dioxide), energy sources, and likely was replete with a
planetary magnetic field sufficient to support the growth of magnetotactic
bacteria.

Imre Friedmann, a senior research fellow at NASA's Ames Research Center in
California's Silicon Valley, also weighed in heavy in support of ALH84001
containing relics of early Martian life. He led an international team
discovering chains of magnetite crystals in the Mars rock, stating that they
are of biological origin. The chains were preserved in the meteorite long
after the bacteria themselves decayed, he said

"We conclude that the chains in ALH84001 are magnetofossils, remnants of
magnetotactic bacteria. No other consistent interpretation would account for
our observations," Friedmann reported at the conference.

Let the data speak

"I think it's fair to say that the data now are looking even stronger than
they did three to four years ago," said David McKay, JSC senior scientist
for exploration and science. McKay headed the team -- that also included
Thomas-Keprta -- which announced to the world in August 1996 that ALH84001
held evidence for past Martian life.

"We're particularly interested in the magnetite data. The only thing that it
fits is a biological magnetite on Earth. This magnetite is so unique and
unusual that we just don't see how it can be made except with the help of
biology. We're really quite confident that we have evidence for primitive
life in the meteorite," McKay told SPACE.com.

"We've come a long way in understanding some of the more specific properties
in the rock," said Everett Gibson, a JSC geochemist, and another original
member of the Mars rock team. "We as a team are more convinced now than when
we presented our results in 1996," he said.

"Let the data speak. There's a lot of people arguing on emotions as opposed
to facts," Gibson told SPACE.com. "Sure the critics are more vocal, but
where's their data?" he said.

Critics corner

Taking issue with any bounty of Martian microbes in the Mars rock is Allan
Treiman, a research scientist at the Lunar and Planetary Institute in
Houston. His detailed studies point to abiotic -- without the presence of
life -- and non-Martian origins for the features claimed to be biological in
ALH84001.

The reported bacteria-shaped objects were formed on Earth, Treiman said,
likely stemming from the Antarctic environment itself, as well as artifacts
from sample preparation, or weathering effects on the Mars rock from
thousands of years residing in Antarctica before being picked up.

Joining Treiman in the skeptics' corner is John Bradley, adjunct professor
at the Georgia Institute of Technology in Atlanta. "Unfortunately, there are
many signatures in the fossil record here on Earth, and probably on Mars,
that look very similar to bacterial signatures. But they are not unique to
bacterial processes," he said.

"Extraordinary evidence hasn't been furnished at this point. The bottom line
is, even though they've found structures in this meteorite, some of which
are consistent with bacterial magnetite, these structures are probably not
unique to bacterial magnetite," Bradley said.

"In science, the onus is on them, not the critics to prove it right,"
Bradley said.

Truth is?

There are "fundamental flaws" in the research by those claiming to have
found evidence for life in ALH84001, said Ralph Harvey, assistant professor
in geology at Case Western Reserve University in Cleveland, Ohio.

"It has all boiled down now to this magnetite. The only defense used is to
claim that these must be biological because nobody has ever published a
detailed description of these in an inorganic setting. The truth is that we
haven't looked," Harvey said. "It's hard to prove a negative hypothesis.
It's hard to test it, but it is essential. It's the difference between
science and faith," he said.

Harvey said that the research community is "tired of following their
footsteps on the wrong path. We're not going to spend our careers testing
straw men that they put up. I think they are caught in a 'moving hypothesis'
mode," he said.

"I'm absolutely uncompelled by the argument for life until alternative
hypotheses are tested - that these things are inorganic," Harvey said.

The debate rests on whether the features found in ALH84001 can be made
non-biologically, said William Boynton, a space scientist at the University
of Arizona in Tucson. "It's not something that can be rigorously ruled out.
But to date, nobody has seen things exactly like this either in nature or
synthesized in the lab," he said.

"I think it's actually coming down now to more a question of philosophy
rather than science. What does it take to constitute a proof?," Boynton
said. "In my view, there's nothing that can be done to move this debate much
further until we bring samples back from Mars," he said.

Secret of the rock

Since the Mars rock was unveiled to the public in August 1996, David McKay
and his team have continued to chip away at disbelievers that ALH84001,
indeed, has something important to say about life on Mars.

But will there ever be closure on the debate? McKay believes so, but it
means pushing the state-of-the-art in analyzing the meteorite.

"It'll be another four or five years before we think we can convince the
community or refute everything we've said. But we have to go to a whole new
level of analysis," McKay said. "I personally think that in five years we
will have solved this question. But that's a minority viewpoint and has to
do with using a lot of techniques that are not commonly used today," he
said.

"We can't really predict what the outcome will be. But we know it's worth
pursuing. It is worth taking the time and effort or we wouldn't be doing
this," McKay said. "I think the secret of the rock is still buried in the
rock. We just have to figure out how to get it out," he said.
Received on Wed 28 Mar 2001 01:43:17 PM PST