NASA says a big asteroid that flew past Earth a couple weeks ago almost certainly won't hit us when it comes back in 19 years.
The asteroid is 1,300 feet wide, but it wasn't discovered until nearly a month after it came within 4 million miles of Earth. That's because smaller asteroids are harder to spot than much larger ones.
NASA said there's only a one in 48,000 chance it will hit Earth next time around.
Meanwhile, researchers say they've found evidence that a massive comet smashed into Earth in the distant past.
They say it exploded after it entered the atmosphere and rained, "a shockwave of fire that obliterated every life form in its path."
Scientists think the heat reached 3,600 degrees and turned parts of the Sahara Desert into glass.