Asteroids racing through the solar system have smashed into Earth before. What are the chances we'll get hit again? Armed with new defensive technologies, scientists are getting ready for the day, a decade, century from now... the day of the asteroid.

An asteroid safely passed by our planet on Saturday night just hours after being detected. Astronomers have labeled the space rock as asteroid 2016 QA2. The rock is estimated to be at least twice as big as the Chelyabinsk meteor that penetrated the atmosphere over Russia in February, 2013.

The asteroid has an estimated size of 111.5 feet (34 meters), although its exact dimension can range between 52-171 feet (16 to 52 meters). The speeding space rock came considerably closer than the moon, as it passed at just 0.22 the Earth-moon distance.

It’s not so unusual that we didn’t notice an asteroid. NASA estimates that over 90 percent of the near-Earth objects (NEOs) larger than 1 kilometre have already been discovered, but so far only 30 percent of the 160-metre (460-foot) NEOs have been found, and less than 1 percent of the 30-metre (100-foot) NEOs have been detected.

These little space rocks are the ones that keep us on our toes, because they're simply too small for us to detect until they get close, but they're big enough to cause some real damage if they actually make an impact.

Asteroid Day is an annual global awareness movement that brings people from around the world together to learn about asteroids and what we can do to protect our planet, our families, communities, and future generations. Asteroid Day is held on the anniversary of the June 30, 1908 Siberian Tunguska event, the largest asteroid impact on Earth in recent history.

It was co-founded by filmmaker Grigorij Richters, B612 Foundation COO Danica Remy, Apollo 9 astronaut Rusty Schweickart and Dr. Brian May, Queen guitarist and astrophysicist. Over 100 astronauts, scientists, technologists and artists, including Richard Dawkins, Bill Nye, Peter Gabriel, Jim Lovell, Alexei Leonov, Bill Anders, Kip Thorne, Lord Martin Rees, Chris Hadfield, Rusty Schweickart and Brian Cox co-signed the Asteroid Day Declaration. Asteroid Day was officially launched on December 3, 2014.