Astronomers spot small space rock just hours before it drops meteorites over Canada

A small space rock was detected just a few hours before hitting Earth's atmosphere and landing in Canada's Lake Ontario on Saturday (Nov. 19). 

The mini-asteroid, less than 3 feet (1 meter) wide, was spotted by astronomer David Rankin at Mount Lemmon Observatory in Arizona, according to SpaceWeather.com. Subsequent observations by other astronomers confirmed that the rock, coming from the direction of the main asteroid belt between the orbits of Mars and Jupiter, was on a collision course with Earth. 

Only three hours after the first detection, the object, since dubbed C8FF042, sliced through the sky above Canada and landed in Lake Ontario, according to NASA. 

According to the European Space Agency (ESA), this was only the sixth case of an asteroid being found just before impact. In March, a Hungarian astronomer detected a somewhat bigger space rock only two hours before it burned up above the northern Atlantic Ocean. 

Related: Asteroid apocalypse: How big must a space rock be to end human civilization?

Eyewitnesses from Toronto and around reported seeing the bright fireball, which lit up the sky on Saturday at about 3:27 EST (0827 GMT). Many meteor and web cameras captured views of the fireball; One stunning video sequence shows the streak of light passing behind Toronto's iconic CN Tower.  

According to NASA, radar stations tracked the meteorite from the altitude of about 9 miles (15 kilometers) to 0.53 miles (0.850 km), where it likely fragmented. Space agency officials wrote that most of the fragments probably fell into Lake Ontario, with some small pieces possibly landing near the towns of Grimsby and McNab. The American Meteor Society has received 59 reports of fireball sightings. 

Small asteroids cross the path of our planet frequently. The smallest ones usually burn up in Earth's atmosphere, leaving behind only the ephemeral light streaks. Fragments of larger rocks can reach Earth as precious meteorites that scientists can study to get a glimpse of the nature of objects in the solar system. 

Bigger rocks, over 65 feet wide (20 m), can cause problems on Earth as the shockwaves their explosions trigger can shatter windows and knock down trees. Larger asteroids can be even more damaging, but the impacts of those are fortunately very rare. 

The international astronomy community is mapping the asteroid population near Earth with the aim to track all potentially dangerous asteroids. Astronomers believe that most of the "planet killers" — bodies more than 0.6 miles (1 km) wide — are already known and none present an immediate danger. However, many smaller rocks capable of causing country-wide damage are still undiscovered.

In September this year, NASA's DART probe smashed into a small asteroid moonlet Dimorphos with the goal of changing its orbit around a parent asteroid Didymos. The experiment was a success, proving that if a future threat is discovered in advance, we may be able to deflect it.

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