Fortunately huge, extinction causing asteroids don't hit Earth very often, but how many are out there? How likely are they to strike? Ettore Perozzi, Head of the Space Situational Awareness office at the Italian Space Agency, explains.
Asteroids can tell us about the origins of the Solar System and maybe even life itself, but they also pose a risk to Earth as many graze past our planet on a regular basis. Find out more about what ESA is doing to protect us through its Planetary Defence Office, part of the Space Safety programme.