In 1908, in the middle of nowhere Siberia, a fairly large object streaked through the sky and exploded over the eastern Siberian taiga. This air blast is estimated to have flattened 80 million trees, killed countless reindeer and three humans, and created a shock wave through the atmosphere that was detected all around the world.

Tomorrow, our show will be highlighting the launches and history of rockets, so we’re going to talk about that June 30 event today instead. Asteroid Day is a new, UN-sanctioned, yearly event held on the anniversary of that bad day in Siberia, and it is a day on which scientists and science communicators work to remind everyone that rocks can still fall out of the sky and kill.

Tunguska isn’t the only human-observed major event. For many of you watching now, the 2013 event in Chelyabinsk was a wake-up call to just how dangerous a twenty-meter space rock can be. Streaking through the early morning sky and observed in security and dashboard cameras, this event included an explosion above the ground, a massive shock wave, and a fair amount of destruction. We are pleased to share that no reindeer are known to have been harmed and no deaths were reported.

Missions like Dawn, OSIRIS-REx, and Hyabusa2 allow us to better study asteroids, and future missions may help us learn to move them. Until we have that tech, we need to watch them and make sure we know when the next big one might be coming. Let’s hope that day is far away.

More Information

Today In Science: The Tunguska Explosion (EarthSky)

Five Years after the Chelyabinsk Meteor: NASA Leads Efforts in Planetary Defense (NASA)