Emergency plan to deflect giant asteroid

Peril above: A spacecraft called DART is scheduled to crash into the asteroid at 15,000 mph.

Are asteroids our biggest threat? Scientists are now working on a plan to protect Earth from Didymos, a giant rock the size of Egypt’s great pyramid — one of 20,000 known near-Earth objects.

Fully 40 miles away, a man was sent flying off his chair. Eight hundred square miles of forest were destroyed, and 80 million trees were flattened. Thousands of animals were killed.

When a meteor, 100 metres-wide, struck a remote part of Siberia at 7:17am on 30 June 1908, it was a near miracle that no people were killed. But locals were so shocked that they believed a god had cursed the area.

Next week, researchers from NASA and the European Space Agency will attend a conference in Rome to discuss the progress of an ambitious mission to deflect an asteroid in space.

The Asteroid Impact Deflection Assessment (AIDA) — a collaboration between the two space agencies — is designed to demonstrate that such a technique could work if we need to protect our planet from a collision with a large space object.

The target of AIDA is a double asteroid called Didymos — consisting of two bodies measuring around 2,560 and 525 feet in diameter respectively — which orbits the Sun between the paths of Earth and Mars.

Apollo 9 astronaut Rusty Schweickart explains that space rocks have struck Earth “millions of times” before.

“It will also happen in the future. But if we humans do our job correctly, this will never happen again.”

About 100 tons of meteoroids enter the Earth’s atmosphere each day and become meteors. Most burn up harmlessly, but records suggest they killed people in ancient China. And as recently as 2013, a meteor exploded above Chelyabinsk in Russia, injuring 1,000 people.

More worryingly, NASA estimates that 2,100 asteroids larger than 1km pass between the Sun and the edge of Earth’s orbit. A collision with one of them could degrade the global climate, destroy crops and threaten everyone on Earth. The largest known asteroids are around 8km wide — and many comets could do similar damage.

Efforts to mine asteroids could help to find them, while groups like the B612 Foundation are trying to develop the technology needed to deflect them. But Schweickart says NASA is not tracking 99% of those which could wipe out a city on Earth — or 90% of those which could devastate countries.

Other factors could also cause the mass extinction of humanity: for example, catastrophic climate crisis, nuclear war or artificial intelligence. But are rocks from space the most worrying threat of all?

Not worth the worry?

We should invest more time and money to tackle it, say some. We know very little about asteroids, so we are unprepared. Unlike other threats, without our intervention, a collision is mathematically certain at some point. It could happen, unannounced, at any time — whereas other threats are more foreseeable.

That is an over-reaction, others respond. The catastrophic strike, which wiped out the dinosaurs, happened 65 million years ago — such events are vanishingly rare. The human race is much more likely to be destroyed by its own hand, so that is where we should focus our attention. Our fascination with asteroids is not rationally justifiable.

You Decide

  1. Are you worried about the threat from asteroids?
  2. Are asteroids the biggest threat facing life on planet Earth?


  1. Write down five questions about asteroids that you would like to ask Rusty Schweickart. Discuss with a partner why you chose those, and what answers you would expect.
  2. Think of one possible (realistic) way that life on Earth could come to an end. Prepare a two-minute talk to your class, explaining how it could happen, how likely it is, and how it could be prevented.

Some People Say...

“If you don’t ponder the end of the world on a regular basis, I don’t think you’re really human.”

Edan Lepucki, US novelist

What do you think?

Q & A

What do we know?
Scientists are working on developing at least two approaches to deflecting potentially harmful asteroids. One strategy involves gently pushing the asteroid slowly, over time, off its course and away from Earth. The other is the gravity tractor. If an asteroid is detected early enough, it could be possible to divert it using the gravity of a spacecraft, according to NASA.
What do we not know?
How seriously we should worry. Emily Lakdawalla, senior editor of The Planetary Society, says that while the asteroid’s close brush with Earth may have sparked some concern, “It is zero per cent danger to us. It’s the kind of thing where you learn about something that you didn’t know about, like things flying close by us, and your inclination is to be scared. But just like sharks in the ocean, they’re really not going to hurt you and they’re really fascinating to look at.”

Word Watch

The strike is called the Tunguska event.
Dan Yeomans of NASA says locals were initially reluctant to discuss the strike as they thought it was a visitation from the god, Ogdy.
Small rocks in space are known as meteoroids. They become meteors (shooting stars) when they enter the Earth’s atmosphere.
These are larger than meteoroids. After a revision of their definition in 2010, the smallest ones are about one-metre wide.
These have a nucleus of ice and dust, and are usually further away from the Sun than asteroids. A comet which passed near Jupiter could pose a threat to Earth.
Luxembourg has recently given 200m euros to support mining. Two private companies in the USA are investing in similar work. This will give them an incentive to help find asteroids.
Scientists at Oxford University have estimated a 9.5% chance of our species being wiped out during the next 100 years.


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