As June 30th is annouced as Asteroid Day 2017, astronaut Hadfield explains why we should take the possibility of collisions with celestial rocks seriously

'Obviously the threat is there': Chris Hadfield on the danger of asteroid strikes

“The Earth gets hit by 50 tonnes of meteorites a day. That’s more than most people think. Normally they are small little grains and burn up but once in a while they are big rocks,” says astronaut Chris Hadfield, who launched himself to stardom by singing David Bowie’s Space Oddity on the International Space Station.

“Occasionally they go over an inhabited part of the world and we see a shooting star. Or they get close to the ground like Chelyabinsk and they do damage. So obviously the threat is there. Obviously,” he says.

Four years ago tomorrow was the day that the Chelyabinsk meteor struck Earth. It was the day for me when the threat posed by asteroids stopped being a largely academic concern and became frighteningly real.

I received a pre-breakfast phone call from an editor at The Guardian, who asked me to look into reports that something had hit Russia. I was sceptical. The first YouTube video I saw was a shaky phone cam of some streets and a loud bang, followed by a view of a thick vapour trail in the sky. Ironically, it didn’t seem convincing.

I found a few more videos. Then I started to come across the dash-cam views of the meteor streaking across the sky and I wasn’t so sceptical anymore.

The editor phoned back. The foreign desk had confirmed that people had been injured in the Chelyabinsk region of Russia by the falling object. A pit opened in my stomach and I realised just how frightening the threat from asteroids actually is.

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The Chelyabinsk impactor was only 20 metres in diameter. It exploded about 30 kilometres above the ground and the shock wave this created damaged more than 7000 buildings in six cities across the region. Most seriously, around 1500 people needed medical assistance for their injuries, which were mostly caused by broken glass from windows shattered by the blast. The only consolation was that no one had died.

“Just in my lifetime there have been countless examples of rocks from the universe hitting the world, some of them big enough to blow out windows and do damage but none of them have caused fatalities that we know about,” says Hadfield.

From orbit, he says it is clear that the Earth is a target. “Look at the Earth from a spaceship and the scars [impact craters] are obvious. The Earth gets hit.”

The question is how to talk about the threat without scare-mongering or sensationalising.

Enter Asteroid Day, the brainchild of filmmaker Grig Richters. He wanted to set up a day to sensibly communicate the threat of asteroids after making 51° North, a film about the devastating collision of an asteroid. He recruited Queen guitarist and astronomer Brian May and set the event in motion in 2015.

“It is obviously a conversation we need to have,” says Hadfield, “What is the right amount of effort to put into rocks hitting the world? I think it is logical to say let’s see how much it will cost to see when we are going to be hit. And once we find one, what can we do about it?”

Hadfield initiated these conversations while he was the president of the Association of Space Explorers (ASE). This is the professional body for astronauts and seeks to allow their members to communicate their unique perspective of the world with the wider public.

A fellow member of ASE, Romanian cosmonaut Dorin Prunariu then became instrumental in orchestrating the UN’s adoption of Asteroid Day. It is widely recognised that any detection and deflection network must be an international endeavour but exactly what shape that might take is still unknown. This is one reason for continuing to engage with the public to raise awareness of the danger.

“[An asteroid strike] is a low probability but extremely high consequence event. So, it shouldn’t be our highest priority but it should be on our list. Asteroid Day is a great way of trying to sharpen people’s awareness and senses. I’m by no means the motive force behind it but I’m happy to be involved in it,” says Hadfield.

Asteroid Day 2017 will take place on 30 June. The press conference featuring leading asteroid experts can be watched in the viewer above. The livestream will begin at 1:30 GMT, 14 February.

Stuart Clark’s latest book is The Search for Earth’s Twin (Quercus Books).