[meteorite-list] Mars Methane 'Not From Meteors'

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 9 Dec 2009 13:50:33 -0800 (PST)
Message-ID: <200912092150.nB9LoX9o011531_at_zagami.jpl.nasa.gov>

http://news.bbc.co.uk/2/hi/science/nature/8402741.stm

Mars methane 'not from meteors'
BBC News
December 9, 2009

The methane found on Mars is not brought to the planet by meteor
strikes, scientists say.

Meteoritic material subjected to high temperatures did not release
enough methane to account for the amount believed to be released on Mars.

The researchers argue that the methane must therefore be created by
geologic or chemical processes, or it is a by-product of microbial life.

The work appears in Earth and Planetary Science Letters.

The origin of the methane on Mars has remained a mystery since it was
first detected in 2004.

Because methane has a limited lifetime in the Martian atmosphere before
degrading, some process must be pumping hundreds of tonnes of it into
the Martian atmosphere annually to keep it at the levels that have been
detected.

Scientists at Imperial College London say they have now ruled out the
possibility that the methane is being constantly deposited by meteorites
landing on the planet.

They heated meteorite fragments to 1,000C, quantifying the gases
produced by measuring how much they absorbed an infrared laser.

They then calculated, based on estimates of how many meteorites impact
Mars annually, how much methane would be released.

They found that just 10kg of methane is produced from meteors each year,
in contrast to the 100-300 tonnes that must be produced to keep the
atmospheric concentration at its current levels.

That suggests that a number of other possibilities, many of which are
based on chemical reactions of the rocks that form the planet's crust.

Alternatively, the gas may be produced by volcanoes or life that
survives beneath the crust - or it may be trapped in chemical cages,
having been produced long ago.

"As Sherlock Holmes said, eliminate all other factors and the one that
remains must be the truth," said study co-author Mark Sephton.

"The list of possible sources of methane gas is getting smaller and
excitingly, extraterrestrial life still remains an option. Ultimately,
the final test may have to be on Mars."

The US space agency Nasa will launch the Mars Science Laboratory in
2011, which will be able to study the methane more closely.

In November, the European and American space agencies signed an
agreement to collaborate on Mars missions that will return to the
planet, starting in 2016.
Received on Wed 09 Dec 2009 04:50:33 PM PST