Blow to panspermia - from the Telegraph
- From: Peter Brooks <Peter.H.M.Brooks@xxxxxxxxx>
- Date: Tue, 07 Aug 2007 07:14:56 -0000
An interesting article that's relevant to our recent discussion on
extraterrestrial life:
"
Ancient glacier creatures brought back to life
By Roger Highfield, Science Editor
Last Updated: 2:14am BST 07/08/2007
Creatures that once lived eight million years ago have been
successfully thawed from the ice of an Antarctic glacier, in an
experiment that sounds like a scene from a science fiction film.
Ancient glacier creatures brought back to life
Scientists found the microorganisms in ice samples from ancient
Antartic glaciers
The feat of revival was managed with as yet unidentified single-celled
microbes and should pose no health issues, say the scientists
However, it does show that evolution of simpler organisms is
complicated by thawing glaciers which allow ancient bugs to contribute
their old genes to modern populations.
The finding is significant, said Kay Bidle, assistant professor of
marine and coastal sciences at Rutgers University, The State
University of New Jersey, because scientists didn't know until now
whether such ancient, frozen organisms and their DNA could be revived
at all or for how long cells are viable after they've been frozen.
Working with Prof Paul Falkowski, Prof Dave Marchant of Boston
University and Prof SangHoon Lee of the South Korea Polar Research
Institute, Dr Bidle melted five samples of ice from the Transantarctic
Mountains ranging in age from 100,000 to eight million years old to
find the microorganisms trapped inside.
The results are reported in the Proceedings of the National Academy of
Sciences.
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"The young stuff grew really fast. We recovered them [the
microorganisms] easily; we could plate them and isolate colonies. They
doubled every couple of days."
By contrast, Dr Bidle said, the microorganisms from the oldest ice
samples grew very slowly, doubling only every 70 days.
"I do not think the readership need worry about the reappearance of
ancient bugs in the environment," said Dr Falkowski.
"But as Antarctic ice melts, ancient genes from these organisms almost
certainly will find their way to the ocean and may be incorporated
with modern microbes. This 'horizontal' gene transfer process has
probably occurred many times in Earth's history and almost certainly
has influenced the evolution of microbes."
Not only were the microorganisms in the eight million year old ice
slow to grow, the researchers were unable to identify them as they
grew, because their DNA had deteriorated, as a result of cosmic rays
that bombard the ice.
This decline was rapid so that every million years or so half the DNA
remained and this find undermines suggestions that icy bodies - comets
- that bombarded the Early earth could have imported genetic material
from outside our Solar System.
In this way, the work limits the idea of panspermia, that life spread
through the cosmos as seeds of genetic material moved about.
"The preservation of microbes and their genes in icy comets may have
allowed transfer of genetic material among planets," they wrote.
"However, given the extremely high cosmic radiation flux in space, our
results suggest it is highly unlikely that life on Earth could have
been seeded by genetic material external to this solar system."
Dr Bidle said the finds were also relevant to the quest to find the
remains of life on Mars: "Years of detailed work on geology and
formation of the debris-covered glaciers in the Transantarctic
Mountains in Antarctica by Dave Marchant and others have revealed
similarities to what has been observed for sub-surface ice on parts of
Mars. So, currently, it is the best proxy we have here on Earth for
potentially similar environments."
"
.
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