We know we live in a cosmic shooting gallery. Who’s got their eyes on the sky, and how will we prevent an asteroid strike if we find a dangerous space rock?
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On the early morning of February 13, 2013, people living in the Chelyabinsk region of Russia awoke to one of the most powerful warnings in recent history. Anyone looking up saw an incredibly bright meteor streak across the sky, brighter than the Sun. Observers said they could even feel the heat of the object as it passed overhead.
Moments later, the shockwave arrived, smashing out windows across a huge region, sending almost 1,500 people to the hospital with various cuts and injuries. It was absolutely amazing that nobody died.
But what was it? According to astronomers, the Chelyabinsk meteor was probably a space rock measuring about 20 meters (or 60 feet across). It struck the Earth’s atmosphere going almost 20 kilometers per second, at such a low angle that it just detonated, raining down debris, but sparing the region the true devastation of this kind of an impact.
The Universe delivered a powerful warning that the Solar System is filled with rocks and debris left over from its formation. And those objects still continue to smash into the Earth.
In fact, one of the most terrifying things about the Chelyabinsk strike is this: the meteor was completely unknown to astronomers before it crashed into the atmosphere. The moment of impact was the moment of discovery.
Today I’m beginning a two part series all about the search for killer asteroids and comets. In part one, we’re going to talk about the risks we face. What kinds of objects are out there, how dangerous are they, and what kinds of observatories and programs are working to find the next impact event.
In part two, we’ll talk about defense. If we do find a potentially dangerous asteroid or comet, what can we do to prevent an impact? We’ll talk about the physics and engineering of moving asteroids, to make the Solar System safer.
It’s not a question of “if” an asteroid will smash into the Earth, it’s a question of “when”. In fact, material from space is impacting our atmosphere all the time. According to NASA, about 100 tonnes of rock and dust gets added to the Earth every day. Once a year, a car-sized chunk of space rock impacts the Earth, exploding as a bright fireball.
A Chelyabinsk-level event is thought to happen once every 60 years or so. In fact, there have been three other recorded events with that kind of energy release in the last century, including the 1908 Tunguska event.
Every 2,000 years or so, an object the size of a football field hits Earth, causing localized destruction. And every few million years, an object comes along that releases so much energy, it would threaten the existence of human civilization.
The problem of course, is that we don’t know when or where these events are going to happen.
And it’s this problem that astronomers are trying to solve first.