[meteorite-list] Scientist Studies Common Rocks for Chemical Clues to Earth's First Organisms

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 29 Dec 2006 09:23:59 -0800 (PST)
Message-ID: <200612291723.JAA18185_at_zagami.jpl.nasa.gov>

http://www.baltimoresun.com/news/health/bal-hs.origins29dec29,0,6082318.story?coll=bal-health-utility

A rocky pathway to life's origins
Research scientist studies common rocks for chemical clues to Earth's
first organisms

By Dennis O'Brien
Baltimore Sun
December 29, 2006

For decades, scientists have looked for clues to the origin of life in
out-of-the-way places: in ancient rock formations, in the heart of
meteorites, in deep-ocean hydrothermal vents and even in the soil on Mars.

But Robert Hazen thinks the secret to learning how life emerged from the
primordial soup may be much closer - in the common rocks that litter his
office at the Carnegie Institution in Washington.

Hazen, a research scientist at Carnegie's Geophysical Laboratory, says
the important thing is how common such rocks are - and how common they
were when the first tiny organisms appeared on Earth.

"The nice thing about minerals is they were everywhere. Tidal pools,
volcanic slopes, undersea vents," Hazen said. "Any place you go had
rocks and minerals."

Hazen and others looking for the secrets of life are motivated by the
most elemental forces of curiosity: If all life evolved from a common
ancestor, shouldn't we try to find it and understand it?

Besides, they say, think of the implications of finding a chemical
pathway to life's origins - given the possibility of habitable planets
scattered across the universe.

"It's one of the greatest questions humans have asked themselves
throughout ??? history," Hazen said. "And if we find there is a chemical
pathway to life, we'll know we're not alone in the universe."

To pry the information he needs from its hiding places, Hazen has
modified an instrument called a microarray. It normally analyzes samples
of DNA, but he uses it to measure how well molecules of certain
chemicals - the ones scientists call the building blocks of life - stick
to his rocks and minerals.

It's just one of the devices that have helped scientists learn about
life's origins since the chase began in 1953. That's when Harold C. Urey
and Stanley L. Miller of the University of Chicago filled enclosed
flasks with gases that they thought would mimic Earth's early
atmosphere. When they struck the gasses with artificial lightning, the
experiment produced amino acids that are precursors to life.

Later research showed that the colleagues were probably wrong about the
makeup of the early atmosphere - but scientists nonetheless credit them
with sparking today's intense interest in uncovering life's origins.

"People may have been thinking about it, but they were the ones who went
into a laboratory and actually did the experiment," said James Ferris, a
professor of chemistry and chemical biology at Rensselaer Polytechnic
Institute and director of the New York Center for Studies on the Origins
of Life.

Scientists probing life's origins have always faced major hurdles. Not
the least is a shortage of clues going back to life's starting point -
an estimated 4 billion years ago.

Here's why: To become living cells, smaller molecules first had to join
and form larger, more-complex organic molecules. For that to happen,
they had to have a central point - a cradle of sorts - where they could
all gather.

"We're trying to see if just the right molecules will stick to the
surface of the minerals" that were available at the time, said Hazen of
his approach, outlined in the December issue of American Mineralogist
and a recent presentation at a National Academy of Sciences conference
in California.

Elsewhere, fossils discovered in Western Australia show the existence of
cyanobacteria - organisms similar to those in today's oceans - some 3.5
billion years ago.

But the fossils give up few hints about how those early life forms
developed. "We have no geological record, no way of looking at all of
this by picking up a rock," said Jeffrey Bada, an expert on life's
origins at the Scripps Institute of Oceanography.

Another issue is where to start looking: The sheer variety of life on
Earth creates a daunting number of possibilities.

Some scientists believe the mix of minerals and compounds around
undersea hydrothermal vents is a good starting point.

Others are intrigued by researchers from Oregon State University, who
discovered an undersea ridge off the Galapagos Islands in 1977 where
one-celled organisms thrive on rock surfaces at depths of more than a
mile. Never exposed to sunlight, they draw energy from other microbes.

Meanwhile, the discovery of amino acids on a meteorite that hit near
Melbourne, Australia, in 1969 has led to speculation that life's
building blocks came from asteroids or interstellar debris falling to Earth.

Some experts look to Mars for clues about life on Earth. Mars was wet in
its early history, with temperatures that could have supported primitive
life-forms. It also has a surface that, unlike Earth, has been frozen in
time, said the Scripps Institute's Bada.

Researchers at Carnegie and Scripps are designing instruments to probe
Martian soil as part of future NASA missions. "There's all sorts of
proposals out there, because we don't know what the answer is," Ferris said.

Another problem: The leap from simple molecules to living cells is
extremely complicated. It requires development of both proteins, which
are necessary for basic life functions, and DNA, a staple for passing
along a survival toolkit to offspring.

In fact, the planet's earliest life-forms may have evolved well before
the arrival of DNA and protein-based cells. The discovery in the 1980s
that ribonucleic acid, or RNA, can splice and join fragments of itself
together in a self-replicating process has led to speculation about a
prehistoric "RNA world" and what may have preceded ours.

That discovery won the 1989 Nobel Prize in chemistry for Sidney Altman
of Yale University and Thomas R. Cech, now president of the Howard
Hughes Medical Institute.

"We think there was a stage even before RNAs. There could have been any
number of things. No one really knows," said Jack Szostak, a genetics
professor at Harvard Medical School and an HHMI investigator.

Scientists say they are years away from discovering what mix of amino
acids, sugars, organic acids and lipids yielded the organic compounds
that evolved into our earliest ancestors.

"The answer you're looking for, whence the origin of life, it's not
there. The information just isn't available yet." said Norman Pace, an
evolutionary biologist at the University of Colorado at Boulder.

But Hazen's microarray could speed up the learning process a bit - no
matter which theory of life's origins turns out to be right. That's
because the molecules that started it all needed a concentration point,
Hazen said.

"We don't have to take a real strong stand on any [of the theories] to
do this work," he said.

In Hazen's testing process, mineral samples are cut up and put into the
microarray in tiny pieces. Specks of amino acids and other organic
molecules are then placed on the minerals to see how well they adhere.
The stickiest combination of molecules and minerals will be considered
candidates for further studies, he said.

It used to take Hazen two months to determine whether a molecule was
actually sticking to one of his minerals. But with the breadbox-sized
microarray, he can conduct thousands of tests in a matter of hours. He
credits Andrew Steele, a Carnegie colleague, with help in designing the
tool.

"We want to know how a molecule of a specific size and shape sticks to a
specific mineral surface. There's a binding that occurs and that process
is still a mystery," Hazen said.

Hazen began probing life's origins in 1996 at George Mason University in
Fairfax, Va., where he also teaches earth sciences. "We were discovering
less and less that was really novel and I thought, why not try to answer
some of life's bigger questions?" he said.

Hazen purchases minerals from dealers around the country and is a
regular at the Tucson (Ariz.) Gem and Mineral Show. "I'm looking for
stuff no one else wants - the most common of minerals because they're
the ones most relevant to the origin of life," he said.

His office collection includes feldspar from Ethiopia, quartz from Hot
Springs, Ark., and calcite crystals from China and Tennessee.

Hazen is aware his work stirs up debate among those who see the creation
of life as a subject best left to theologians. But he believes in a
creator - and sees evidence of it all the time in nature's complexities.

"The study of science is a study of creation," he said. "You can't look
at nature and not have a feeling there's something greater than yourself
at work."
Received on Fri 29 Dec 2006 12:23:59 PM PST