It is the stuff of nightmares and, until now, Hollywood thrillers. A huge asteroid is on a catastrophic collision course with Earth and mankind is poised to go the way of the dinosaurs.To save the day, Nasa now plans to go where only Bruce Willis has gone before. The US space agency is drawing up plans to land an astronaut on an asteroid hurtling through space at more than 30,000 mph. It wants to know whether humans could master techniques needed to deflect such a doomsday object when it is eventually identified. The proposals are at an early stage, and a spacecraft needed just to send an astronaut that far into space exists only on the drawing board, but they are deadly serious. A smallish asteroid called Apophis has already been identified as a possible threat to Earth in 2036. … A 1bn tonne asteroid just 1km across striking the Earth at a 45 degree angle could generate the equivalent of a 50,000 megatonne thermonuclear explosion. Attempting to break it up with an atomic warhead might only generate thousands of smaller objects on a similar course, which could have time to reform. Scientists agree the best approach, given enough warning, would be to gently nudge the object into a safer orbit. … Matt Genge, a space researcher at Imperial College, London, has calculated that something with the mass, acceleration and thrust of a small car could push an asteroid weighing a billion tonnes out of the path of Earth in just 75 days.
The Earth has a long history of asteroid strikes. Thirty five million years ago, a 5km-wide asteroid ploughed into what is now Chesapeake Bay, in the US, leaving an 80km crater. In 1908, an asteroid devastated swaths of Siberia when it exploded mid-air with the force of 1,000 Hiroshimas. The theory that the dinosaurs were wiped out by a huge asteroid striking Mexico 65m years ago is controversial since scientists uncovered rocks from the crater predating the extinction of the dinosaurs by 300,000 years.
…A near miss, when asteroid QW7 came within 4m km of Earth in September 2000, led Liberal Democrat MP Lembit Opik to declare: “It’s not a case of if we will be hit, it is a question of when. Each of us is 750 times more likely to be killed by an asteroid than to win this weekend’s lottery.” – guarduk