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. Possible tiny, flatulent aliens. BBC NEWS | Science/Nature | Methane on Mars could signal life | 
