----- Original Message ----- From: [EMAIL PROTECTED] Sent: Tuesday, September 03, 2002 1:32 PM To: undisclosed-recipients:; Subject: No Place For Life To Hide From Mars Express
ESA Science News
http://sci.esa.int
03 Sep 2002
No place for life to hide from Mars Express
Of all missions sent to Mars only one, the Viking 26 years ago,
has dared to search for life. Its only conclusive result was that
finding proof of extraterrestrial life proved to be much harder
than expected. Second attempts never followed. Until now. ESA's
Mars Express, the next mission to the Red Planet and the first
European one, has an ambitious goal. To be launched in 2003, Mars
Express will be the first spacecraft after Viking to search for
direct and indirect evidence for past or present life on Mars.
This time, scientists are equipped with more knowledge and
insight in how to detect Martian life. The chances of success
look very good.
The expectations regarding life on Mars have changed
substantially since the Viking missions. Today's scientists
are considering several alternatives:
1. Martian life exists, but the lifeforms are so small you can
barely see them and they probably live underground;
2. Martian life is not only small but also dead and extinct
by now, so the search is for fossils and not for living
organisms; and
3. there is no life on Mars now and there never has been.
Each of the two Viking landers, launched in 1976, carried three
biological experiments. All of them searched for microbes or
microorganisms, or their 'signature', in soil samples. All
three experiments, based on different concepts, quickly
produced positive results. The thrill died down as scientists
soon realised that a non-biological process could easily
explain most of the results. Surprisingly, the non-biological
process that had tricked scientists had not been anticipated
by anyone prior to the launch.
ESA's Mars Express will arrive at Mars in December 2003 and
will follow a strategy quite different from that of the Viking.
It consists of an orbiter plus a lander, called Beagle 2, "as
an homage to the ship on which Charles Darwin found the
inspiration to write his theory of evolution," says Agustin
Chicarro, ESA Project Scientist for Mars Express, also
pointing out that "indeed this mission could be as
revolutionary as Darwin's ideas because it is the first one
after the Viking to search for life."
A key difference between Mars Express and the Vikings is that
now scientists are aware that they should also look for past,
fossilised life. A few biological experiments are not enough.
Mars Express's scientists will combine many different types
of test findings, for example, to help discard contradictory
results.
Some of the evidence will be indirect, mostly focused on the
search for water. The Mars Express orbiter will have seven
instruments on-board, apart from the lander Beagle 2. One of
these instruments will image the entire planet in full color,
in 3D, at a resolution of about 10 metres. Another will map
the mineral composition of the surface with great accuracy.
"These data will be key to determine how much water there was
in the past, and from that you can estimate how much water
there is left," says Chicarro.
A third instrument on-board the Mars Express orbiter will
search for water below the surface, to measure the thickness
of the layer of ice or permafrost, that is, a thick subsurface
layer of soil that has a temperature below 0 C all year round.
Other studies will determine the amount of water in the
atmosphere and the water cycle: how the water is deposited
in the poles and how it evaporates depending on the seasons.
The search for direct evidence of past or present biological
activity will be the task of the lander, Beagle 2. Once
deployed, in an area that was probably flooded in the past,
Beagle 2 will unfold its robotic arm where most of the
instruments are located. Beagle 2 carries several instruments,
among them a gas analysis package that will determine whether
carbonate minerals on Mars, if they exist, have been involved
in biological processes. If there are certain gases on Mars,
such as methane, that scientists believe can only be produced
by organisms living either on the surface or below it,
Beagle's 'nose' will detect them.
The feeble Martian atmosphere cannot prevent ultraviolet
radiation from the Sun killing potential life. For this
reason, it is important to get samples from places below the
surface, under large boulders, and within the interiors of
rocks. Beagle 2 will collect samples with a mole able to
crawl short distances across the surface, about 1 centimetre
every six seconds, and to dig down to 1.5 metres deep. If
the digging proves to be hard, a grinder will help access
the rocks' protected interior. With all these available tools,
Mars Express will be the best mission ever to discover life
on Mars. There can be no place for life to hide from it.
USEFUL LINKS FOR THIS STORY
* More about Mars Express
http://sci.esa.int/marsexpress
* Chances of life are linked to water
http://spdext.estec.esa.nl/content/doc/90/30352_.htm
IMAGE CAPTIONS:
[Image 1:
http://sci.esa.int/content/searchimage/searchresult.cfm?aid=9&cid=12&oid=30347&ooid=30348]
D. radiodurans, a so-called extremophile, here on Earth.
Microscopically small, it withstands attacks from acid baths,
high and low temperatures, and even radiation. It would
probably resist Mars's highly oxidative environment also.
Copyright © Michael J. Daly, Uniformed Services University
of the Health Services
[Image 2:
http://sci.esa.int/content/searchimage/searchresult.cfm?aid=9&cid=12&oid=30347&ooid=26723]
Mars Express in orbit around Mars.
[Image 3:
http://sci.esa.int/content/searchimage/searchresult.cfm?aid=9&cid=12&oid=30347&ooid=28279]
The Beagle 2 lander, to be carried on ESA's Mars Express, is
equipped with a suite of instruments designed to look for
evidence of life on Mars.
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