[meteorite-list] Dig Deeply to Seek Life on Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 29 Jan 2007 11:14:21 -0800 (PST)
Message-ID: <200701291914.LAA24904_at_zagami.jpl.nasa.gov>

http://www.agu.org/sci_soc/prrl/2007-03.html

Dig deeply to seek life on Mars
AGU Release No. 07-03
29 January 2007

American Geophysical Union
University College London
Joint Release

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Public Information Manager
Phone: +1-202-777-7507
E-mail: pweiss at agu.org

UCL Contact: Alexandra Brew
Phone: +44-(0)20-7679-9726
E-mail: a.brew at ucl.ac.uk

WASHINGTON - Probes seeking life on Mars must dig deeply into young
craters, gullies, or recently exposed ice to have a chance of finding
any living cells that were not annihilated by radiation, researchers
report in a new study. One promising place to look for them is within
the ice at Elysium, site of a recently discovered frozen sea, they say.

Current probes designed to find life on Mars cannot drill deeply enough
to find living cells that may exist well below the surface, according to
the study. Although these drills may yet find signs that life once
existed on Mars, the researchers say, cellular life could not survive
incoming radiation within several meters [yards] of the surface. This
puts any living cells beyond the reach of today???s best drills.

The study, to be published 30 January in the journal Geophysical
Research Letters, maps cosmic radiation levels at various depths, taking
into account surface conditions in various areas of Mars. The lead
author, Lewis Dartnell of University College London, said: "Finding
hints that life once existed - proteins, DNA fragments, or fossils - would
be a major discovery in itself, but the Holy Grail for astrobiologists
is finding a living cell that we can warm up, feed nutrients, and
reawaken for studying."

"Finding life on Mars depends on liquid water surfacing on Mars,"
Dartnell added, "but the last time liquid water was widespread on Mars
was billions of years ago. Even the hardiest cells we know of could not
possibly survive the cosmic radiation levels near the surface of Mars
for that long."

Unlike Earth, Mars is not protected by a global magnetic field or thick
atmosphere, and for billions of years it has been open to radiation from
space. The researchers developed a radiation dose model and quantified
variations in solar and galactic radiation that penetrates the thin
Martian atmosphere down to the surface and underground. They tested
three surface soil scenarios and calculated particle energies and
radiation doses both on the surface and at various depths underground,
allowing them to estimate the survival times of any cells.

The team found that the best places to look for living cells on Mars
would be within the ice at Elysium, because the frozen sea is relatively
recent - it is thought to have surfaced in the last five million years - and
so has been exposed to radiation for a relatively short period of time.
Even here, though, any surviving cells would be out of the reach of
current drills. Other ideal sites include young craters, because the
recently impacted surface has been exposed to less radiation, and
gullies recently discovered in the sides of craters. Those channels may
have flowed with water in the last five years and brought cells to the
surface from deep underground.

The study was funded by the United Kingdom's Engineering and Physical
Sciences Research Council (EPSRC), the Swiss National Science
Foundation, and the Swiss State Secretariat for Education and Research.

------------------------------------------------------------------------

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The paper and this press release are not under embargo.

      Title:

"Modelling the surface and subsurface Martian radiation environment:
Implications for astrobiology"


      Authors:

Lewis Dartnell:
    Centre for Mathematics and Physics in the Life Sciences and
    Experimental Biology (CoMPLEX), University College London, London,
    United Kingdom;

L. Desorgher:
Physikalisches Institut, University of Bern, Bern, Switzerland;J. M. Ward:
    Department of Biochemistry and Molecular Biology, University College
    London, London, United Kingdom;

A. J. Coates:
    Mullard Space Science Laboratory, University College London,
    Dorking,United Kingdom.


      Citation:

Dartnell, L. R., L. Desorgher, J. M. Ward, and A. J. Coates (2007),
Modelling the surface and subsurface Martian radiation environment:
Implications for astrobiology, Geophys. Res. Lett., 34, L02207,
doi:10.1029/2006GL027494, in press.


Contact information for authors:

    * Lewis Dartnell: +44-(0)7799-532-842 (mobile phone; omit "0" if
      calling from outside the United Kingdom) or l.dartnell at ucl.ac.uk

AGU is a worldwide scientific community that advances, through unselfish
cooperation in research, the understanding of Earth and space for the
benefit of humanity.
Received on Mon 29 Jan 2007 02:14:21 PM PST