A meteor that exploded over Russia in February was "a wake-up call" for humanity, according to scientists studying the event.
Where did it come from? What was it made of? What can be done if we know a meteor or asteroid is going to hit Earth?
A look at some of the best video from the Russian Meteor. More than 400 people were injured after it flew over a Russian city.
The American Meteor Society has verified over 300 witness sightings of a meteor in at least 13 US states.
Stretching from Ontario down to the southern state of North Carolina, there are still over 100 reports yet to be reviewed, said Mike Hankey, an observer for the American Meteor Society.
"This was most certainly a fireball seen over a good portion of the eastern states," said Robert Lunsford, the society's fireball coordinator.
"It happened at a good time, around 8 o'clock on a Friday night, when a lot of people were out to see it," Lunsford said.
A NASA scientist has told the Associated Press that social media reports of a meteor on the US east east seem to be consistent with the behaviour of a meteor shower.
Donald Yeomans, manager of NASA's Near-Earth Object Program in California, said: "it's unusual to have so many people see it."
Bloomberg News has reported that there have been sightings of a possible meteor, seen on the US Eastern Seaboard.
FLASH: Reports of a possible meteor seen on U.S. Eastern Seaboard; sightings from upstate New York to northern Virginia.
Dr Karl Kruszelnicki from the University of Sydney said not enough money is being spent on researching a researching meteor collision. Speaking on the BBC Radio World Service, he said:
Chillingly we spend more money on making movies about rocks that can hit the earth than we do about looking for the actual rocks.
Dr Kruszelnicki said there were two possible ways to averting a potential meteoric disaster: painting the meteor white, so that the sun exerts more pressure on it, thus pushing past earth, or using a rocket to push it out of the earth's path. He explained:
We send a whole lot of people who normally spend their time painting the whole surface white, over a few years that pressure might nudge it off by a few thousand kilometres over a few years and that would just miss us as opposed to just hitting us.
If we have less time, then we have to think about getting up there with rockets. Pushing the rockets hard against the rock and then firing it and trying to nudge it off with sheer Newtonian mechanics.
Tim O'Brien, associate director of the University of Manchester's Jodrell Bank Observatory, has described the metoer which exploded in southern Russia on Friday as a "completely abnormal experience".
It made a sonic boom in the atmosphere, and that hit buildings and shattered windows. That is what seems to have caused the injuries.
It's a completely abnormal experience. This thing appeared in the distance, raced over the horizon and was followed up 30 seconds or a minute later by a huge boom as the shockwave hit the ground. I can imagine that would be very frightening.
Russian authorities have reportedly sent a 20,000-strong team to the Ural Mountains to help with the rescue and clean-up operation after a meteor struck the area.
The 10-ton meteor, thought to be made of iron, exploded over the Chelyabinsk region in southern Russia yesterday morning.
More than 1,000 people were injured when the meteor, which was travelling at over 54,000mph, streaked through the atmosphere and created a sonic boom.
Hundreds of people were injured when glass shattered in countless windows in the area.
According to Russia's Academy of Sciences, the meteor broke apart 30-50km (20-30 miles) above the Earth's surface, releasing several kilotonnes of energy - the same as a small atomic weapon - the BBC said.
Huge chunks of space rock crashed to earth after a meteor exploded in the skies over Russia, with the power of an atomic bomb.
It was travelling so fast it created a sonic boom that shattered thousands of windows which, in turn, injured more than seven hundred people around the Russian city of Chelyabinsk.
ITV News correspondent Paul Davies reports:
As a meteor streaked at supersonic speed across the clear skies of Russia, people cried out in panic that the world was ending. Hundreds were injured, as the shockwaves from a huge sonic blast shattered windows and buckled roofs and walls.
Fragments of the exploding meteor fell to earth in central Russia, around the city of Chelyabinsk, a thousand miles east of Moscow.
ITV News correspondent Paul Davies reports:
CCTV footage captured the moment teachers and pupils scattered as the Russian meteor hit. The blast shattered the windows of the building in the Chelyabinsk region of the country.
Despite it not making contact, nearly 1,000 people were injured after the meteor exploded over Chelyabinsk in the Ural Mountains this morning.