Danger from outer space.

• Author: Potenza, Alessandra
• Position: SCIENCE

An asteroid wiped out the dinosaurs 65 million years ago. What are we doing to avoid their fate?

On Feb. 15, 2013, the morning skies above Chelyabinsk, Russia, lit up with a blinding flash. A few moments later, a loud boom and a forceful shock wave shattered windows across the city, injuring about 1,500 people.

The dazzling fireball wasn't a missile but a 65-foot meteor * hurtling at a speed of more than 40,000 miles an hour that exploded about 19 miles above the city. It released 30 times more energy than the atomic bomb dropped on Hiroshima in 1945. Had the meteor burst over a densely populated city, like New York or Los Angeles, it might have caused thousands of deaths.

"We'd have a lot more than broken windows, that's for sure," says Edward Lu, a former NASA astronaut.

The Chelyabinsk meteor, which had been completely undetected, served as a wake-up call to people all over the world that space rocks pose a real danger to Earth.

Every day, about 80 tons of debris hit our planet. The vast majority is tinier than a grain of salt, but space rocks the size of basketballs arrive once a day, and objects as large as cars show up about once a week. Typically, space rocks burn in Earth's atmosphere, but occasionally they're big enough to hit the ground.

These meteorites can cause major damage (see box, facing page). In 1908, a 120-foot meteor moving at a speed of 9 miles per second detonated in the sky over Siberia, in Russia. The explosion flattened 80 million trees over an area of about 800 square miles. (The area was largely uninhabited, so no one died.)

A month after the recent Chelyabinsk meteor, which caused $30 million in damage, the U.S. House of Representatives' Committee on Science, Space, and Technology held a special session to assess the government's ability to detect asteroids and prevent collisions. In 2014, Congress doubled NASA's budget for detecting and tracking asteroids, to $40 million. And this year, the budget spiked to $50 million, a more than tenfold increase since 2008.

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