Out of 600,000 bits of space debris, we're about to be hit by one the size of a bus

IT IS the size of a bus, weighs in at ten tonnes, is loaded with toxic chemicals and is hurtling to Earth at 22,000mph. No-one, unfortunately, knows where it is going to land.

US government officials admitted yesterday that they have lost control of a spy satellite and said it will smash into the planet within weeks.

The unnamed surveillance satellite is just one of an estimated 600,000 pieces of space junk currently flying above our heads.

Experts have warned that humanity has made "a zoo" of space with the amount of dead satellites and rubbish.

The spacecraft may have lost power as much as a year ago, but there is no estimate of where it could hit or what damage it could cause.

Only one person has ever reportedly been struck by a piece of space debris – a woman in Oklahoma who was hit in the shoulder by a piece of material but uninjured.

UK bookmakers last night placed the odds of being struck by this US spy satellite at at least 20 billion to one.

But while many bits of space junk are guided to crash down safely into the sea, the lack of control over the satellite means its operators cannot say where it will land.

Professor John Brown, Astronomer Royal for Scotland, said: "We are making quite a mess up there – it's a bit of a zoo. And it's going to get worse with China and India up there. It's a big, big problem and if you get into space, you can get damaged by tiny bits of paint travelling in the region of 10km per second or 22,000mph. The energy is huge.

"If it hit land it could be like a small plane crash, but nobody has ever been killed by a falling space object. Anything that's not designed for re-entry would probably break up. The more catastrophic thing would be an asteroid hitting the earth."

There are more than 600,000 objects in space measuring more than 1cm, according to the European Space Agency's Meteoroid and Space Debris Terrestrial Environment Reference. And the US Strategic Command has a catalogue of about 12,000 objects in space. Only 600 are said to be operational satellites.

NASA's Orbital Debris Program Office states that spacecraft re-entering because of decaying orbits or controlled entry usually break up at altitudes between 84 and 72km from the ground. Larger items break up lower in the atmosphere and lighter objects such as solar panels typically break up around 90-95km.

More than 100 tonnes of man-made objects make an uncontrolled re-entry each year. Of satellites that re-enter, only about 10-40 per cent of the mass of the object is likely to reach the ground.

Gordon Johndroe, a spokesman for the National Security Council, said of their uncontrolled satellite: "Appropriate government agencies are monitoring the situation. Numerous satellites over the years have come out of orbit and fallen harmlessly

"We are looking at potential options to mitigate any possible damage this satellite may cause."

The spacecraft is understood to contain the rocket fuel hydrazine, a colourless liquid with an ammonia-like odour, and a toxic chemical that can harm anyone who gets in contact with it.

An uncontrolled re-entry could risk exposure of US secrets, said John Pike, director of the defence research group GlobalSecurity.org.

Spy satellites typically are disposed of through a controlled re-entry into the ocean so that nobody else can access the spacecraft, he said.

Mr Pike also said it is not likely the threat from the satellite could be eliminated by shooting it down with a missile, because that would create debris that would then re-enter the atmosphere and burn up or hit the ground.