When American government representatives asked NASA head Charles Boden what the best response to a large asteroid headed for Earth would be, his answer was simple: ‘Pray’.

NASA claims to have detected upwards of 97% of the ‘planet killer’ asteroids in the solar system – objects six or seven miles wide, similar to the ones which killed the dinosaurs.

We should have warning if such an object approached, but there are currently no technologies which could stop it.

Media reports often focus on ‘mid-sized’ asteroids, which would destroy a city on impact – but the destructive power of a ‘planet killer’ is difficult to even imagine.

‘Bad Astronomy’ expert Phil Plait said that the entire Cold War arsenal of nuclear weapons would have amounted to a millionth of the power of the explosion that wiped out the dinosaurs.

This week, the BBC spoke to experts to offer a step-by-step guide to what would happen if a six-mile asteroid hit Earth – based on the fossil record of the asteroid which killed the dinosaurs.

MORE: Hang on – is that a 200-ft metal UFO orbiting an asteroid near Earth?

The asteroid hit Earth at 40 times the speed of sound – causing an explosion seven billion times bigger than the Hiroshima bomb.

A Mushroom cloud rising white, blotting horizon, in OP Ivy, Mike shot atomic bomb test blast. (Photo by Time Life Pictures/Us Air Force/The LIFE Picture Collection/Getty Images)
A Mushroom cloud rising white, blotting horizon, in OP Ivy, Mike shot atomic bomb test blast. (Photo by Time Life Pictures/Us Air Force/The LIFE Picture Collection/Getty Images)

Kirk Johnson of the Smithsonian National Museum of Natural History said, ‘Basically you are looking at a 10km-diameter bullet.

‘The physics is just extraordinary. You get just this incredible explosion, incredible earthquakes, incredible tsunamis, and then anywhere within several hundred kilometres of the site you have building-size blocks raining down on the landscape.’

(Picture: Getty Images)
(Picture: Getty Images)

Tsunamis up to 900ft high would have raced out of the blast site, while earthquakes rippled through the Earth. The air blast from the explosion would have flattened forests for thousands of miles.

EBEPPH Tyrannosaur and triceratops dinosaurs during impact winter just after asteroid impacted earth surface during cretaceous period -
(Picture Getty)

But the worst part was yet to come. The asteroid’s impact had vapourised a huge chunk of Earth’s surface, which shot into space and surrounded the Earth.

The plume of burning rock turned into tiny droplets of glass, which rained down onto our atmosphere – heating the air so much that plants on the surface caught fire. Our planet turned into an oven.

(Picture: MIT)
(Picture: MIT)

The asteroid dust rained down onto our planet for months – and combined with soot from fires all around the world, to plunge the planet into a dark, long winter.

Near-Earth asteroid, artwork

Extreme heat killed animals around the world – while acid rain polluted the water. On the dark surface, many plants could not photosynthesise.

Johnson says, ‘On land, everything’s burned and dead, and everything big is starving to death.’

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