A mysterious blue-green streak of light was spotted moving across the sky over the US Southwest last night, prompting a flood of 911 calls from Phoenix to Los Angeles, CNN reports. There were no reports of impact or damage and NASA says it believes the object was probably a fireball caused by a fragment of an asteroid falling to Earth.
"We can't say 100%," but the object was almost certainly a fireball or a meteor small enough to have disintegrated before it hit the ground, the chief of NASA's Near-Earth Object Program tells the AP. The bluish-green color, he says, was probably caused by magnesium or nickel inside the asteroid fragment. "They make an impressive show for such a small object," he says. "It's a natural phenomenon and nothing to be concerned about." (Read more NASA stories.)