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In the past few months, conclusive evidence has been found that Mars once had water on its surface, but one greater question remains: Was there, or is there still, life on Mars as well? Scientists may be on the brink of answering that question with an equally conclusive 'yes', as convincing evidence has been detected by Nasa's Curiosity rover. An instrument on the rover identified spikes of methane that scientists believe may have come from bacteria-like organisms on the surface - and it could be the first alien life ever detected. Scroll down for video Nasa scientists in California have revealed evidence that suggests there is life on Mars based on readings taken by the Curiosity rover (shown). They say methane spikes on the planet could be produced by bacteria. And at the moment there is no alternative explanation for the spikes

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Nasa authors are cautious about jumping to conclusions, but conclude that 'methanogenesis' - the formation of methane by microbial bugs known as methanogens - may be one answer to the riddle.