Caused by meteors entering Earth's atmosphere at a lower trajectory and speed than usual, the space rocks burn brighter than Venus in the sky, which astronomers designate as a fireball.
Visible across the United States for the whole of this month, the fireballs have become a source of mystery for NASA scientists and other sky-watchers around the world.
Observing the phenomenon for the past 50 years, NASA say that February's fireballs are different from other months but the reason why is not clear.
'These fireballs are particularly slow and penetrating,' said Peter Brown, a physics professor at the University of Western Ontario in Canada.
'They hit the top of the atmosphere moving slower than 15 kilometers per second (33,500 mph), decelerate rapidly and make it to within 50 kilometers (31 miles) of Earth’s surface.'
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