An asteroid measuring 150ft (46m) will zip past Earth next week.
The megarock will pass within 17,000 miles (27,400km) of the planet - the closest known approach ever for an object of this size.
But Nasa scientists said today that there is no reason to worry. They insist there is absolutely no chance of a collision next Friday.
The asteroid - considered small - will come closer to Earth than many high-flying communication satellites.
It will be visible through binoculars or telescopes as it zooms by at 17,400mph (28,000kph), with Indonesia the best viewing location. Other prime viewing spots are eastern Europe, Asia and Australia.
The asteroid was discovered last February.