Is an asteroid going to hit Earth?
It’s Asteroid Day, and our friends at All About Space magazine have asked asteroid researcher Professor Alan Fitzsimmonds 5 questions about the threat space rocks pose to life on Earth, how we detect potential Earth-trajectory planet-killers and what we can do about them. Here are some of the highlights from their chat, or you can scroll to the bottom of the page to watch the full interview.
What would happen if even a small-ish asteroid hit us?
“A 1-kilometre object would seriously perturb the entire environment of the Earth… if it’s in the sea you’ve got tidal waves and if it’s on land you’ve got earthquakes, the fireball and the ejecta cloud.
“You’ve got a lot of material thrown up into the atmosphere and that’s not from the asteroid – that’s from the Earth’s crust. This is the stuff that’s gouged out to form the crater… it basically blocks the sunlight, starts killing of crops and disturbing the food chain.
“Something as small as 200-300m across would certainly affect something the size of a small country or state.
What could we do about a potential asteroid impact?
“If you’re talking about something on it’s last impact trajectory – something that’s going to hit us in the next few weeks or days, then all we can do is civil defence – evacuate the area… but for objects that might reach the ground and cause significant damage, the likelihood is that we would have years, if not decades of warning.
“What we would do would depend on the amount of time we had: if we’ve got ten or 20 years then we’ve got quite a few technologies we can use. One is the kinetic impactor, where we slam a spacecraft into the asteroid that nudges it into a different orbit.
“If you’re dealing with a smaller object or a longer timescale, then we’ve got a wonderful technique called the ‘Gravity Tractor’ where instead of hitting the asteroid, you hover over it and you just let Newton’s force of gravity from the spacecraft pulling gently on the asteroid into a slightly safer orbit. The nice thing about that is that if you control the spacecraft, very gently over a few years, then that’s a nice controlled way of moving the asteroid into a different orbit.
“If you’ve got a very short timescale and the object’s too big, say 500 metres or larger and just a couple of years, then neither of those two techniques will work. Then you’d be looking at some kind of blast deflection, either a large amount of conventional explosives or a nuclear device. We’d explode it 10-100m above the surface of the asteroid. What that does is vaporise quite a bit of the asteroid – as that material moves one way the rest of the asteroid moves the other way quite rapidly, into a different orbit.”
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