What should we do if an asteroid heads our way?

Chris Smith put this question to astronomer Matt Bothwell...

Matt - I think the first thing just to clarify is that we do get hit by asteroids all the time. We are being bombarded by stuff from space all the time, but he general rule is that the smaller the thing is, the more common they are. If you’re looking at the really really small stuff like a grain of sand and smaller, we’re getting hit by this stuff all the time, so every day. But the bigger you go the rarer things get hit, so we get hit by say football sized things maybe once a day, but once you go up to the really really big things that get quite scary and we need to be worried about, we’re looking at every few million years or rarer. The last really big thing was 65 million years ago - it was the asteroid that wiped out the dinosaurs.

If we’re going to be on Earth for the long term, we do need to start worrying about these things and start thinking about the future. There are people that are planning for these things. I think my favourite thing about this is that the person who’s in charge of this is NASA. His job title is planetary defence officer which is like maybe they coolest this job title in the world.

We have a couple of things we can do. There’s broadly two classes of solution: we can either deflect the asteroid so just push it out the way so it doesn’t hit Earth, or we can destroy it. If we’re going to deflect it, there’s something we could do like launch something heavy at it like we’re playing a giant game of snooker and kind of hit it out of the way. Or there’s a proposal that we can kind of blast asteroids with lasers and hopefully evaporate enough mass from the asteroid that it will change its orbit that way.

There are some really ‘out there’ solutions like coating asteroids with reflective materials and letting sunlight do the the work, so if we were a coating an asteroid with something reflective then maybe the force from all the photons from the sun would eventually push the asteroid out of the orbit.

Chris - That’s called the YORP effect isn’t it: The Yarkovsy-O’Keefe-Radzievskii-Paddack effect, I believe? That's why we call it the YORP effect!

Matt - I didn’t know that - there you go! But the other alternative is also just destroying it. I think if you’re going to do that, the obvious thing to use is a nuclear weapon but it gets a bit politically tricky because there are very strict laws against using these.

Chris - It’s very dangerous as well of you start firing nukes off the planet surface?

Matt - That’s right, yeah.

Chris - So, bottom line?

Matt - We’re safe for the time being. There’s nothing anywhere near us and it’s good that we’re thinking about these things now and planning for the future.