Close Encounter: Asteroid Zips By Earth

While most Americans were fast asleep Sunday night, an asteroid came within 270,000 miles of hitting Earth - about the same distance between our planet and the moon, and a close call in space terms.

The asteroid called 2004-XP-14 traveled at 11 miles per second, or 40,000 mph, and was nearly 1,300 feet in diameter.

If it had struck Earth, the damage would have been extensive - especially if it had hit a city or highly populated area, said Ben Oppenheimer, an astrophysicist from the American Museum of Natural History in New York.

In 1908, an asteroid hit Siberia and charred everything within a 700-mile radius.

"No one realized what had happened until afterward," Oppenheimer said. "It would be a much bigger deal if one hit the ocean because you're basically punching a hole in the middle of the sea, and all that water has to fall back into itself. So you get tsunamis that are a whole lot worse than what we saw two years ago in Asia."

It may seem like a plot from an action movie, but the threat of being hit by an asteroid is real. Oppenheimer said we must prepare for it.

"The question is a question not of if but when," he said. "What we're seeing today is an important warning shot. This stuff does happen. After all, this is how our moon was formed - an asteroid slammed into the Earth, and the moon broke off during the collision."

A Future Threat

Oppenheimer said that in 2029, an asteroid called Apophis, named for the Egyptian god of darkness and chaos, would come within 20,000 miles of Earth - close enough to hit some weather satellites.

The asteroid would make a return trip in 2036 and come even closer to Earth, he said, adding that there was a one in 40,000 chance that Apophis would crash into the planet, or could land in the Pacific Ocean, creating tsunamis throughout the Pacific Rim.

"A few years ago, the scientific consensus placed a much greater likelihood on Apophis hitting the Earth, something like one in 10," Oppenheimer said. "Only time will tell."

Astronomers have mapped out about 800 potentially hazardous asteroids, although none is on course to strike Earth.

Mapping continues, and Congress ordered NASA to create a catalog of at least 90 percent of those objects by 2020.

If an asteroid hits Earth, Oppenheimer says there are only two things that people can do: Move out of its way or move the asteroid itself.

"In the movies, you see them blowing up the asteroid with a nuclear weapon or a laser or something like that," he said. "But in reality, this would never work because you would just be breaking up the asteroid in many pieces that would then break through the Earth's atmosphere and wreak havoc on a possibly larger scale."

"The best thing to do, actually, is to fly a spaceship up to the asteroid and attach itself, thus creating enough gravitational pull hopefully to change the asteroid's course."