[meteorite-list] With a Big Assist From NASA, UW-Madison Launches Astrobiology Push

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 31 May 2007 13:44:05 -0700 (PDT)
Message-ID: <200705312044.NAA20731_at_zagami.jpl.nasa.gov>

http://www.news.wisc.edu/13842

With a big assist from NASA, UW-Madison launches astrobiology push
by Terry Devitt
University of Wisconsin-Madison
May 31, 2007

With the help of a $6.5 million grant from NASA, Wisconsin researchers
will join the hunt for extraterrestrial life and early life on Earth by
developing techniques and instruments to read the chemical signatures
living organisms leave in rocks and minerals.

With the new award, University of Wisconsin-Madison scientists and their
collaborators from the University of Georgia and the Jet Propulsion
Laboratory (JPL) will become a key part of NASA's Astrobiology Institute.

"The long-term goal is to understand when life began on Earth, what are
the criteria for determining that life existed on another planetary
body," says Clark Johnson, the UW-Madison professor of geology and
geophysics leading the new effort. "What we're looking for is the
signature of past life as preserved in minerals."

If life existed elsewhere in our solar system or beyond, odds are it
would have been single-celled organisms such as bacteria, which can
leave a chemical trail preserved in stone. Such is the case with
microbes on Earth. Scientists have developed a bevy of techniques to
read those chemical signatures to understand something about life that
existed on Earth hundreds of millions or even billions of years ago.

Earth, in fact, will be the laboratory for the new initiative as
researchers seek to refine their understanding of the chemical
impressions left by ancient bacteria and other microorganisms. Such a
baseline will give scientists an interpretive framework for analyzing
samples from Mars and other places beyond our planet that may have once
harbored life.

Such context was lacking with the Allan Hills meteorite, a suspected
piece of Mars found in Antarctica and theorized to be one of the oldest
relics of our solar system at 4.5 billion years old. The meteorite made
news in 1996 with the publication of a paper suggesting that tiny
features in the rock might be artifacts of ancient Martian life.

That evidence, it turns out, is now discounted by most scientists. Thus,
any future sample purported to harbor evidence of extraterrestrial life
will be the subject of intense scientific scrutiny. "The bar is really
high," says Johnson. "The (scientific) community is not going to believe
it unless the interpretive framework behind it is fully developed."

To help achieve that, Johnson's group plans an isotopic approach as a
way to ferret out the signatures of life from rocks that may be hundreds
of millions or billions of years old. Most elements have different
masses called isotopes, and very subtle changes can occur during
biological reactions.

"Geologists are good at going back in time, and we will explore the
isotopes in very ancient rocks," Johnson explains.

The allure of chemical isotopes as biosignatures, Johnson says, resides
not only in their ability to identify the chemical fossils of past life,
but also in their great durability.

He explains that any sample will have a complicated history and may have
endured many changes over long periods of time. For example, minerals
from another planet may have been exposed to large doses of ultraviolet
radiation for billions of years, or geologic processes that can
potentially change their composition. But the isotopic makeup of
elements that were cycled by living creatures, Johnson notes, tend to
resist such change.

His group will first compile an inventory of organic materials such as
carbon, and in simulated planetary environments, test their
survivability to assemble a plausible inventory of things to look for on
another planet.

"We'll look for terrestrial analogs that we can really pull apart," says
Johnson.

In recent years, scientists have found numerous Earthbound microbes that
live in extremely hot and chemically forbidding environments, and it has
been long known that microbial life can live off of and process elements
such as iron. Knowing the kinds of signatures they leave behind will be
a big help when samples from other planets become the subject of
scientific scrutiny.

The new project, Johnson hopes, will exert influence on future NASA
missions. Ultimately, his group will help with the development of a
miniature mass spectrometer and other instruments that could be deployed
by a probe to search for signs of past life on Mars or other planets.
Received on Thu 31 May 2007 04:44:05 PM PDT