[meteorite-list] New Case for Oldest Life on Earth
baalke at zagami.jpl.nasa.gov
Fri Apr 23 16:44:33 EDT 2004
New Case for Oldest Life on Earth
By Robert Roy Britt
22 April 2004
Using a method never applied to rock from ancient Earth, researchers have
found possible signs of biological activity dating back nearly 3.5 billion
years, earlier than any other agreed-upon discovery of life on this planet.
The primordial life appears to have eaten rocks to survive.
Meanwhile, separate work is turning up intriguing similar structures in Mars
rocks found on Earth, though no claims of life have yet been made with
regard to this ongoing Martian investigation.
If the terrestrial finding is confirmed, it means life was thriving not long
after this world had been presumably sterilized several times over by
asteroid and comet impacts that were common in the earliest era of the solar
system, which is about 4.6 billion years old.
The researchers found microscopic tubes in ancient, glassy lava that they
say were created by microbes eating into the lava after it cooled on the
ocean floor. Similar signatures of life, including genetic material, have
been found in lava that formed more recently in Earth's history. Scientists
generally agree that the tubes in the more modern lava were indeed creating
by boring organisms.
The 3.5-billion-year-old tubes contain carbon and traces of carbonates that
could represent organic material left behind by the primitive organisms. The
research was led by Harald Furnes atNorway's University of Bergen and is
reported in the April 23 issue of the journal Science.
Of life, evolution and sex
Separately, scientists are engaged in an ongoing debate over purported
microfossils in rock found in Australia, also said to be about 3.5 billion
years old, and even older "graphite inclusions" in rocks from Greenland.
Meanwhile, the oldest solid evidence for life dates back 3.2 billion years.
Nobody knows how life began. Scientists aren't even sure if it started on
Earth first or was transported here by Mars rocks or in the bellies of
comets. They do know that Earth was initially inhospitable and probably dry
as a bone when it formed about 4.5 billion years ago.
Pockmarks on the Moon testify to an early history of asteroid and comet
impacts that might have killed any living things on Earth or thwarted the
development of life for the first few hundred million years. (Earth would
have a similar frequency of scars but they were folded inward and eroded
Or, others argue, catastrophe may have been the mother of evolution, wiping
out all but the hardiest life and forcing certain favorable mutations. For
example, one study suggests a later, milder bout of cosmic poundings led
primitive creatures down the path of mutation toward their first sexual
The latest findings
The newest discovery was made in lava that was once buried at the bottom of
the sea but is now exposed in the so-called Barberton Greenstone belt in
"Our data come from entirely different rocks than those in which the search
for early life has done previously," study leader Furnes told SPACE.com.
"The biosignals we have applied are different from those previously used,"
Furnes said. "I think comparing our results with those on which the
controversies presently are going on, would be like comparing apples and
Little is known about the microbes and what they ate, Furnes explained. They
apparently created some sort of microenvironment that dissolved the glassy
lava rock, in order to drill into it.
"We know very little about this, and from the biosignals we see in the
Barberton lavas it is impossible to tell," Furnes said. "Attempts to culture
microbes that settle and dissolve young glassy lavas are few. From the few
data that exist, however, it appears that the microbes gain energy from
In an analysis of the work in Science, other researchers not involved in the
study offered varying perspectives.
"To me, it's unequivocal that the textures they see were created by
microorganisms," petrologist Martin Fisk of Oregon State University told the
journal. "I think they've got the best evidence I've seen for life at that
Microbial geochemist Jennifer Roberts of the University of Kansas called the
evidence compelling but said it's not a smoking gun. She said nonbiological
processes can create similar tube-like structures.
In a telephone interview, Fisk said he is "still open" to the interpretation
that the tubes were created by something other than living things, but he
added that no one has demonstrated what nonbiological process would actually
be at work.
Fisk has been aware of Furnes' work for some time, and separately he's been
trying to find similar microscopic signatures of life in Mars rocks that
have been found on Earth. So far, he said, he's not found anything that
conclusively suggests life on Mars. But in a few grains of the mineral
olivine, from Mars meteorites, he's noted shapes similar to those found in
terrestrial rocks by Furnes and others.
Fisk and his colleagues presented their preliminary findings last month at
the Lunar and Planetary Science Conference, held in Houston.
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