It was the inspiration for Asteroid Day, but what exactly happened at Tunguska in Siberia on 30 June 1908? Asteroid researcher Arnaud Bourdoux looks back to an eyewitness report of the largest asteroid impact in recorded history.

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.

Access the other "Asteroid Day selfies"