When I tell people that I spend my days testing the possibility of life on Mars they usually reply in one of two ways. ‘No seriously, what do you do?’ is only slightly more common than the wittier ‘So you’re not holding out for much fieldwork, then?’ Astrobiology is a bright young discipline, aiming to answer some of the most fascinating questions within science and dinner-table conversation alike. Does life exist ‘out there’ among the pinpricks of light in the heavens, or are we alone in the cosmos? No current scientific field fires people’s fascination more than the quest for extraterrestrial life, and a large proportion of students have cited the reason for continuing science is their interest in astrobiology. For now many astrobiologists’ money is on Mars, our planetary neighbour, as it was once a lot like Earth.