Modern Martian hunting involves looking for the tiniest evidence of life. But when presenter Marnie Chesterton found out that a scientist she was meant to be chatting to about cleanliness had previously worked for NASA, the topic of space bugs turned out to be too intriguing to ignore, especially when a CrowdScience listener asked us a question on a similar theme. Could Earth's microbes hitch a ride on our missions to Mars and colonise the Martian soil? As the European Space Agency's ExoMars venture gears up to launch a rover in 2020 that aims to find out whether there is, or has ever been, life on Mars, we head to the programme's clean rooms and Mars Yard - a giant planet-simulating sandpit - to find out. Marnie meets space engineers whose job is to prevent microbial contamination of Mars whilst creating robots that can find signs of life on the Red Planet. And she discovers that planetary protection is not all about remote aliens: Could tiny Martians have already arrived here on Earth via a meteoric hitch hike?

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Presenter: Marnie Chesterton

(Picture: Mars from the Hubble Space Telescope. Credit: NASA)