A six tonne Nasa satellite is set to fall uncontrolled out of orbit, potentially raining debris over swathes of the planet including Britain, the US space agency has admitted.
The $750 million (£468 million) Upper Atmosphere Research Satellite (UARS) satellite, launched 20 years ago to study climate change, is set to breach the atmosphere within weeks.
In a new alert issued this week, officials warned pieces could land in densely populated areas on six continents including parts of Britain, Europe, North and South America and Asia.
Nasa claimed the risk to public safety from the “dead” satellite – which is orbiting just over 155 miles above the earth with an inclination of 57 degrees – was “extremely small”.
But senior space agency officials admitted they were “concerned” about the risk to billions of people when it starts falling uncontrolled out of orbit at any stage from later this month.
Nasa admitted more than half a tonne of metal from the satellite, which ran out of fuel in 2005, will survive as the majority it will burn up after entering Earth's atmosphere.
While Nasa did not know the exact areas it will fall, the projected danger zone has been narrowed to areas between 57 degrees north and 57 degrees south of the Equator.
These areas cover six continents and billions of people and three oceans.
"Things have been re-entering ever since the dawn of the space age; to date nobody has been injured by anything that's re-entered," said Gene Stansbery, Nasa’s orbital debris chief.
"That doesn't mean we're not concerned."
Last year, a Pentagon report warned that space was so littered with debris that a collision between satellites could set off an “uncontrolled chain reaction” capable of destroying the communications network on Earth.
The volume of abandoned rockets, shattered satellites and missile shrapnel in the Earth’s orbit is reaching a “tipping point” and is now threatening the $250 billion (£174bn) space services industry, according to the US Defense Department's interim Space Posture Review.
Meanwhile in a report earlier this month, the National Academy of Sciences admitted that scientists had “lost control” of the space environment.
