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Rochester - Nov 2, 2001

In what seems a cross between Jules Verne's Journey to the Center of the
Earth and H. G. Wells' The Time Machine, researchers from the University
of Rochester are burrowing deep underground into the most ancient regions
of the globe to find the lost world where life began.

The endeavor, called The Mission to Early Earth, is part of the NASA
astrobiology program. Astrobiology literally means "star life," but the
NASA program is looking for life anywhere beyond our planet. To do that,
however, an astrobiologist needs to know what he or she is looking for in
the first place.


"If we're going to look for evidence of life on Mars or beyond, then we
have to know what we're looking for," says Ariel Anbar, professor of earth
and environmental science at the University. "There is so much we don't
know about the origin and early evolution of life. What chemicals must be
present? What kind of atmosphere helps life start? What are the factors we
haven't even thought of?

"If you want to understand the probability of life being elsewhere, what
that life might be like, and what the course of evolution might be, then
you should be studying the only planet known to harbor life, and study the
history of that planet."

Anbar is a member of one of NASA's astrobiology teams and a geoscientist,
studying the planet to learn about its inhabitants. The greatest hurdle in
trying to form a picture of what the world was like when life first formed
is the scarcity of study samples. Old Earth simply doesn't exist anymore
-- on the surface.

"We don't have a time machine, so we're stuck with old rocks," says Anbar.

"But there aren't very many places you can find rocks that are billions of
years old that haven't been ruined by exposure, so we're going to go
subsurface."

"Subsurface" means drilling a couple hundred meters into the oldest known
rock formations in the world. Anbar has just returned from Australia with
his team on an exploratory mission to scout sites in parts of the Earth's
crust that date to nearly 2.5 billion years old -- more than halfway back
to the Earth's birth -- a time when the only life on the planet was
bacteria.

The NASA-funded trip to the Outback turned up a number of possible
drilling sites that Anbar thinks may yield samples of the Earth's
environment that have remained frozen in time. Though there are some sites
in the world that boast rocks as old as 3.8 billion years, the Australian
rocks are relatively undisturbed by weathering and geological processes.

Anbar's team is especially excited at the chance to pull organic molecules
from the ancient rock bed. Such molecules can speak volumes about the
organisms that produced them and should shed light on the course that
evolution took in life's infancy.

The first life forms may have had a biochemistry substantially different
than today's, which means astrobiologists investigating Mars or other
worlds would need to be looking for something totally unlike anything they
may have assumed.

Anbar hopes to discover in what kind of environment astrobiologists should
expect to find basic life. NASA hopes to launch space telescopes in the
near future that will be able to pick out light from planets around
distant stars.

But what kind of telescope NASA builds will depend on what scientists are
looking for -- should it be tuned for an oxygen atmosphere or methane, or
something else entirely? The answer to that will come from work like that
of Anbar and his colleagues.

The Earth's basic chemistry was very different billions of years ago than
it is now. It's widely accepted that the amount of oxygen in the
atmosphere rose dramatically around 2.2 billion years ago, but there are a
number of factors scientists don't know, not the least of which is, what
completely changed the entire planet's atmosphere?

Anbar explains that the classical argument is that that was the time
period when photosynthesis evolved and created oxygen, but there's good
evidence that oxygen-producing photosynthesis is much too old, leaving
scientists stumped when trying to explain the oxygen surge.

Scientists don't really know the exact living conditions on early Earth,
and until they find evidence of the makeup of the atmosphere trapped
inside ancient rocks, they'll have nothing but speculation.

"The odds are that we'll come across some surprises," says Anbar. "Some
recent work by members of our team found that eukaryotes, the microbial
line that humans came from, might have existed as early as 2.7 billion
years ago.

That's much earlier than a lot of people thought, which means there was a
lot more diversification of biology back then. So maybe we'll learn that
life was almost inevitable, a kind of by-product of our Earth's formation.

Or maybe we'll learn that we're more rare and special than we ever
imagined."

Astrobiologists Looks to Mars, Earth, and elsewhere for information on origins of life and human species.