Methane on Mars could signal life [now]

[Ivan Seeking]

Could it be...? :eek:

Methane has been found in the Martian atmosphere which scientists say could be a sign that life exists today on Mars.
It was detected by telescopes on Earth and has recently been confirmed by instruments onboard the European Space Agency's orbiting Mars Express craft.

Methane lives for a short time in the Martian atmosphere so it must be being constantly replenished.

There are two possible sources: either active volcanoes, none of which have been found yet on Mars, or microbes. [continued]

http://news.bbc.co.uk/2/hi/science/nature/3577551.stm

[Nereid]

Methane occurs in comets; carbon is found in carbonaceous meteorites; several million (?) tonnes of extra-(martial?) material falls on Mars each year ... how much methane in Mars' atmosphere arises from these sources?

Given that methane has a short life in the martian atmosphere, what is the annual rate of methane production implied by these results (in tonnes/year)?