Mars Express's OMEGA uncovers possible sites for life (Forwarded)

ESA News
http://www.esa.int

20 April 2006

Mars Express's OMEGA uncovers possible sites for life

By mapping minerals on the surface of Mars using the European Space
Agency's Mars Express spacecraft, scientists have discovered the three
ages of Martian geological history -- as reported in today's issue of
Science -- and found valuable clues as to where life might have developed.

The new work shows that large bodies of standing water might only have
been present on Mars in the remote past, before four thousand million
years ago, if they were present at all. Within half a billion years,
these conditions had faded away.

The results come from the Observatoire pour la Mineralogie, l'Eau, les
Glaces et l'Activité (OMEGA) instrument on board Mars Express. In one
Martian year (687 Earth days) of operation, OMEGA mapped 90 percent of
the surface, allowing the identification of a variety of minerals and
the processes by which they have been altered during the course of
Martian history. The maps have allowed a team of scientists, led by
Professor Jean-Pierre Bibring, Institut d'Astrophysique Spatiale (IAS),
Orsay (France), to identify three geological eras for Mars.

The earliest, named by the authors as the 'phyllosian' era, occurred
between 4.5-4.2 thousand million years ago, soon after the planet
formed. The environment was possibly warm and moist at this time,
allowing the formation of large-scale clay beds, many of which survive
today.

The second era, the 'theiikian', took place between 4.2 and 3.8 billion
years ago. It was prompted by planet-wide volcanic eruptions that drove
global climate change. In particular, the sulphur these eruptions
belched into the atmosphere reacted with the water to produce acid rain,
which altered the composition of the surface rocks where it fell.

Finally, there was the 'siderikian', the longest lasting of the Martian
eras. It began sometime around 3.8-3.5 billion years ago and continues
today. There is little water involved in this era; instead, the rocks
appear to have been altered during slow weathering by the tenuous
Martian atmosphere. This process gave Mars its red colour.

The eras are named after the Greek words for the predominant minerals
formed within them. The one most likely to have supported life was the
phyllosian, when clay beds could have formed at the bottom of lakes and
seas, providing the damp conditions in which the processes of life could
begin.

However, there are still question marks. The team points out that the
clay beds might have been formed underground, rather than in lakebeds.

"Hydrothermal activity below the surface, the impact of water-bearing
asteroids, even the natural cooling of the planet could all have
promoted the formation of clay below Mars' surface. If so, the surface
conditions may always have been cold and dry," said Bibring.

After this initial period, water largely disappeared from the planet's
surface either by seeping underground or being lost into space. Except
for a few localised transient water events, Mars became the dry, cold
desert seen by spacecraft today. This new identification of clay beds on
Mars provides high-priority targets for future Mars landers that seek to
investigate whether Mars once harboured life.

"If living organisms formed, the clay material would be where this
biochemical development took place, offering exciting places for future
exploration because the cold Martian conditions could have preserved
most of the record of biological molecules up to the present day,"
concluded Bibring.

Note to editors

The full results are published in the 21 April issue of the journal
Science. The article, 'Global Mineralogical and Aqueous Mars History
Derived from OMEGA/Mars Express Data', is by Jean-Pierre Bibring, Yves
Langevin, Francois Poulet and Brigitte Gondet (Institut d'Astrophysique
Spatiale - IAS, Orsay, France), John F. Mustard (Brown University,
Providence, USA), Raymond Arvidson (Washington University, St.Louis,
USA), Aline Gendrin (Institut d'Astrophysique Spatiale - IAS, Orsay,
France & Brown University, Providence, USA), Nicolas Mangold (IDES,
Orsay Campus, France), P. Pinet (Observatoire Midi-Pyrenees, Toulouse,
France), F. Forget (LMD - Univ. Paris 6, France), and the Mars Express
OMEGA team.

For more information

Jean-Pierre Bibring, Institut d'Astrophysique Spatiale - IAS, Orsay (France)
E-mail: jean-pierre.bibring @ ias.u-psud.fr

Agustin Chicarro, ESA Mars Express Project Scientist
E-mail: agustin.chicarro @ esa.int

Fred Jansen, ESA Mars Express Mission Manager
E-mail: fjansen @ rssd.esa.int

* Looking at Mars
http://www.esa.int/SPECIALS/Mars_Express/index.html

Related articles

* Buried craters and underground ice -- Mars Express uncovers depths of Mars

http://www.esa.int/SPECIALS/Results_...ZTULWFE_0.html
* Mars Express evidence for large aquifers on early Mars

http://www.esa.int/SPECIALS/Results_...1UULWFE_0.html
* Mars Express radar reveals complex structure in ionosphere of Mars

http://www.esa.int/SPECIALS/Results_...4UULWFE_0.html
* Mars Express discovers new layer in Martian ionosphere

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Related links

* Mars Express instruments
http://www.esa.int/SPECIALS/Mars_Exp...C75V9ED_0.html

IMAGE CAPTIONS:

[Image 1:
http://www.esa.int/esaCP/SEM117OFGLE_index_1.html]
Thanks to its mapping of the Martian surface, the OMEGA instrument on
board ESA's Mars Express has identified clay beds which may have
supported the development of life in the past, between 4.5 and 4.2
thousand millions years ago. So, these findings provide exciting sites
for future Mars rovers to explore.

The image shown here is a perspective false-colour view of the Mawrth
Vallis region on Mars, derived from the HRSC instrument (ESA/DLR/FU
Berlin (G. Neukum)) onboard Mars Express.

Credits: ESA/OMEGA/HRSC

[Image 2:
http://www.esa.int/esaCP/SEM117OFGLE...html#subhead1]
This image shows the global distribution of hydrated (water-rich)
minerals as discovered by the OMEGA instrument on board ESA’s Mars
Express. The map is superimposed on an altitude reference map of Mars
built with data from the MOLA instrument on board NASA's Mars Global
Surveyor. The red marks indicate the presence of phyllosilicates, the
blue ones indicate sulphates, the yellow ones indicate other hydrated
minerals.

Credits: IAS/OMEGA/ESA

[Image 3:
http://www.esa.int/esaCP/SEM117OFGLE...html#subhead2]
Hydrated minerals in Marwth Vallis on Mars

The left image shows a view of the Marwth Vallis region of Mars, as seen
by NASA Mars Global Surveyor’s MOLA instrument. The OMEGA instrument on
board ESA’s Mars Express has mapped hydrated sites in this area, as
shown in the right image (OMEGA data superimposed on the MOLA map). The
hydrated minerals are not found in the channel (blue arrow) as one would
expect, but in the eroded flanks and the cratered plateau (red arrow).

Credits: IAS/OMEGA/ESA

Andrew Yee wrote:

The eras are named after the Greek words for the predominant minerals
formed within them. The one most likely to have supported life was the
phyllosian, when clay beds could have formed at the bottom of lakes and
seas, providing the damp conditions in which the processes of life could
begin.

Fresh clay is currently being formed at the black smokers:
http://www.asu.edu/clas/csss/csss/News/life.html
Clay is produced by the union of aluminum (+3) and silicate (-4),
which results in an unusual molecule bearing a residual negative
charge.
Because of the charge, clay (aluminum silicate) is slow to
settle out and is propelled toward the sea shore by the waves.
Hence aluminum silicate, in the form of anorthite, is found
on the shores of lunar mare (the highlands) and, as kaolinite,
on the banks of Columbia Hills in Gusev.
The average depth of black smokers is 2.1 km. To achieve the
same hydrostatic pressure on Mars, oceans had to be 6.3 km
deep. Perhaps, during the phyllosian era (4.5-4.2 Ga) Mars was
submerged to a similar extent as Europa or Titan. John Curtis