Europe and Russia have launched a spacecraft in a joint search for signs of life on Mars.
An unmanned craft, part of the ExoMars programme, blasted off from Kazakhstan at 9.31am today, starting a seven-month journey through space.
The mission will hunt for methane in the Martian atmosphere and determine whether it is generated by geology or biological processes.
The gas is largely produced by living organisms, and so its presence could prove that life once existed on the Red Planet.
The two missions will cost over £900m, but if traces of life are found this could be one of the biggest discoveries of all time.
Planetary scientist Dr Peter Grindrod, from Birkbeck, University of London, who is funded by the UK Space Agency, said: "It's incredibly exciting.
"This is a series of missions that's trying to address one of the fundamental questions in science: is there life anywhere else besides the Earth?
"Finding that life exists elsewhere in the solar system would be a huge discovery, so the evidence has to be strong.
"As they say, extraordinary claims require extraordinary evidence."
Meanwhile, enjoy that #ExoMars lift off again pic.twitter.com/gcUf2SMEZw
— ESA (@esa) March 14, 2016
