NEW YORK— The idea that the orbiting chunks of interplanetary rocks called asteroids could hit the Earth and wipe out cities, or even life itself, is a familiar theme in space-based adventure films. But according to three just-released scientific studies in the journals Nature and Science, the likelihood that dangerous asteroids will enter Earth’s atmosphere may be greater than previously believed.
On February 15 of this year, the world was inundated with dramatic video images of a 19-meter-wide meteor streaking across the sky above Chelyabinsk, Russia at nearly 67,000 kilometers per hour. Well over 1,000 people were injured by the event, mostly from the blinding flash and from broken window glass. Still, according to physicist Paul Wiegert of the University of Western Ontario and an author of a study of the Chelyabinsk meteor just published in the journal “Nature”…
“… Chelyabinsk didn’t really create as much damage as we might have expected, and that’s a good thing. The flip side is that we are now starting to discover that events like the Chelyabinsk event are occurring more frequently than we had originally anticipated. But we’ll have to wait a little while longer and collect a little more information before we can know for sure," said Wiegert.
Wiegert adds that collecting that information about orbiting asteroids the size of the one that exploded over Chelyabinsk, then determining their path relative to Earth, is a difficult job using conventional earth-based telescopes.
“Larger asteroids are relatively easily seen with telescopes because they are fairly big. Much, much smaller objects are much more common and frequently hit the earth as meteorites - shooting stars, falling stars and things like that. So we see the bigger objects and we see the smaller objects relatively well. But the Chelyabinsk event kind of falls into the gap between the two," he said.
At a recent panel of the Association of Space Explorers in New York, physicist and former astronaut Ed Lu warned there is little time to lose. He said there are about 10,000 known asteroids orbiting our region of the solar system - that’s just one-thousandth of the number scientists believe could actually be there. Lu's B612 Foundation is planning to help launch a space-based infrared telescope in 2018 that can detect the heat emitted by asteroids, map their position and orbit, then provide a warning in time to mount an international effort to deflect the more dangerous ones.
“You cannot deflect an asteroid that you haven’t found. And the technology exists, the know-how exists and we realized that the cost of finding and tracking these things, the telescope to do that, is about what it cost to build a large freeway overpass," said Lu.
Paul Wiegert says he’s fascinated by the Chelyabinsk event and would welcome the launch of an infrared space telescope to locate similar asteroids.
“But I don’t think the Chelyabinsk event has really increased our perception of the danger. You won’t have any difficulty finding someone who thinks we should be spending more money looking for more asteroids. But I don’t think anybody in the asteroid community is sleeping any less soundly because of that event," he said.
Nevertheless, officials at NASA’s Near Earth Object program, which scans the heavens for dangerous objects, say the space agency is reassessing what size rocks to look for and how often they are likely to hit.