[meteorite-list] New Type of Earth Ecosystem Could Be Found On Other Planets

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:55:47 2004
Message-ID: <200201161936.LAA08309_at_zagami.jpl.nasa.gov>

http://www.nature.com/nsu/020114/020114-7.html

Life, as it was in the beginning?

A new type of Earth ecosystem could be found on other planets.

JOHN WHITFIELD
Nature Science Update
January 17, 2002

Scientists have found a community of microbes unlike anything else on Earth.
Conditions in this ecosystem could mimic those on Earth when life began, and
might exist elsewhere in today's Solar System.

Home to the microbes is a hot spring 200 metres beneath the US state of
Idaho. Their lives owe nothing to the Sun. They generate energy by combining
hydrogen from rocks with carbon dioxide, releasing methane as a by-product.
These 'methanogens' belong to an ancient group related to bacteria, called
the Archaea.

While drilling into a hot spring where there is no organic carbon to feed
more conventional life, Frank Chapelle of the US Geological Survey in
Columbia, South Carolina, and his colleagues identified the microbes living
there from their DNA sequences1.

They were shocked to find that more than 90% of the organisms in the spring
were methane-producing Archaea. The technician "freaked out," recalls
Chapelle, assuming she'd made a dreadful mistake. In most places, such
microbes make up only 2 or 3% of microbial life.

Life - in space and time

Biologists have speculated for many years that hydrogen-powered ecosystems
could exist beneath the ground. The methanogen community suggests they were
right, says astronomer and astrobiologist Richard Taylor of the Probability
Research Group in London.

"As long as there's subsurface water and enough chemical fuel, you can get
microbial life," says Taylor. He thinks that life began in such
environments: "It's life on the surface that's unusual," he says.

Many bodies in the Solar System and the Universe could harbour similar
conditions. "I suspect it's going to turn out that life is extremely
common," says Taylor.

Mars and Jupiter's moon Europa have both been suggested as places where life
could exist on hydrogen, today or in the past. If this is so, says
microbiologist Julian Hiscox of the University of Reading, UK, it will be
several kilometres below the surface, well beyond the reach of any
investigations so far.

Probing these environments is going to cost "an awful lot of money", warns
Hiscox. A cheaper alternative, he says might be to look for biologically
produced methane in martian meteorites on Earth.

Also, Hiscox says, the geological activity necessary to produce hydrogen may
have stopped long ago on Mars, and be absent altogether on Europa.

The finding may give us an insight into life in time as well as space.
Chapelle thinks that hydrogen may have been accessible and abundant enough
on the young Earth to provide the energy for the earliest life.

References

  1. Chapelle, F. H. A hydrogen-based subsurface microbial community
     dominated by methanogens. Nature, 415, 312 - 315, (2002).
Received on Wed 16 Jan 2002 02:36:24 PM PST