A U.S. satellite the size of a bus will break up in the atmosphere as soon as this Thursday, raining debris on the Earth -- but scientists can't say when and where the wreckage will strike.
The satellite is expected to fall apart into 26 pieces as it burns through the atmosphere. The largest piece will be about the size of a fridge.
Scientists have been unable to pinpoint where the debris will fall and will only say it will probably be between northern Canada and the southern tip of South America on an 800-kilometre wide path.
NASA and U.S. military officials tracking the satellite say they will have a better idea of where it may crash about two hours before it hits, which they say will most likely be on Friday.
NASA says the odds of a person being hit by part of the disintegrating satellite are one in 3,200. That means the odds of you, the reader, being personally hit by space junk is actually one in 21 trillion.
The chance you will be hit by lightning this year is one in a million.
Most likely the pieces will land in water or in uninhabited land, Space.com reporter Denise Chow told 麻豆影视 Channel.
"For now, that covers pretty much most of the planet," she said. "There's no need to be concerned."
Carried into orbit by the space shuttle Discovery 20 years ago, the 5.4-tonne Upper Atmosphere Research (UAR) Satellite was used to study chemical components of the atmosphere and various light transmitted by the sun. The satellite was switched off in 2005.
Modern satellites come equipped with the ability for a controlled re-entry but the UAR was launched before that became commonplace.
Additionally, modern satellites are made with materials that will burn up on re-entry.
Chow says there is a lot of debris in Earth's orbit and that it has "reached a critical point."
