Old rocks the key to life on Mars
- From: alan@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx (Alan)
- Date: Thu, 8 Dec 2005 10:40 +0000 (GMT Standard Time)
http://news.bbc.co.uk/1/hi/sci/tech/4502018.stm
By Jonathan Amos
BBC News science reporter, San Francisco
A French scientist believes Europe's next mission to Mars should target some of
the oldest rocks on the planet if it wants to find evidence of past life.
Jean-Pierre Bibring has identified areas that were in contact with water just
after the planet's formation.
In one such region, known as Marwth Vallis, conditions could have been stable
long enough for life to start.
Prof Bibring is pushing for Europe's ExoMars rover, an 580m-euro robotic
vehicle, to be sent there in 2011.
He said: "Marwth Vallis is a good site, too, because the altitude is close to
zero.
"You have to have a site very low on Mars for the parachutes to work."
Persistent water
The scientist from the Institute of Space Astrophysics, Orsay, was speaking here
at the Fall Meeting of the American Geophysical Union.
He made his remarks as Europe's space ministers gathered in Germany to approve
the ExoMars rover. An official announcement signing off the project will be made
on Tuesday.
ExoMars will carry a drill and a suite of instruments to study surface materials
for evidence of past or present biology.
And when mission managers come to decide where to send the rover, they will be
listening closely to Prof Bibring's views.
He is the principal investigator on Omega, an instrument on the Mars Express
orbiter that is mapping the minerals in the Red Planet's surface rocks.
It can see materials that were formed over long time periods in the presence of
large amounts of liquid water.
What is fascinating is that these hydrated minerals - so called because they
contain water in their crystalline structure - were produced in the first few
hundred million years after the planet was created. In other words, the rocks
they make up are more than four billion years old.
Benign for life
Crucially, these are not the sulphate minerals seen by the US Mars rovers but a
different class of hydrated minerals, known as phyllosilicates - more familiarly
called clay minerals.
In Bibring's opinion, it is far more likely that ExoMars will find evidence of
life laid down in these rocks than if it were to look at the sulphates
documented by the US vehicles.
"Phyllosilicates trace the moment when liquid water was perennial and
persistent - something not necessary to make sulphates. To make clay minerals
requires long-standing bodies of water and [for life to form] you need that - at
least with the experience we have from Earth."
This puts Marwth Vallis and other clay locations - such as Arabia Terra, Terra
Meridiani, Syrtis Major, and Nili Fossae - high on the list of possible ExoMars
targets.
And it pushes down the list the sulphate locations such Meridiani Planum and
Gusev Crater currently being inspected by the US Mars rovers. Their sulphates
were formed in acidic conditions - a challenging environment for any lifeform to
evolve.
It is a point echoed last week by US rover scientist Dr Andrew Knoll of Harvard
University.
He observed: "Life that had evolved in other places or earlier times on Mars, if
any did, might adapt to Meridiani conditions, but the kind of chemical reactions
we think were important to giving rise to life on Earth simply could not have
happened at Meridiani."
Jean-Pierre Bibring says the instruments on ExoMars should be equipped to look
for large carbon molecules in amongst the clays of Marwth Vallis as a possible
signature of past life.
http://news.bbc.co.uk/1/hi/sci/tech/4502018.stm
See Al, no shortage of Geology stories from where I am sitting, but then I don't
live in a country where they teach "Intelligent Design" to schoolkids.
Alan
http://www.veloceraptor.free-online.co.uk/enigma.html
http://veloceraptor.blogspot.com/
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