Asteroid watch
January 25, 2012
When a comet or similar object exploded in the atmosphere above the Tunguska River in Siberia in 1908, the blast destroyed millions of trees. Since the region was uninhabited, no lives were known to be lost.
But Alan Harris of the German Aerospace Center (known by its German acronym, DLR) said if the object had come closer to a city, the results would have been catastrophic.
To guard against such possibilities, 13 space and research agencies from Europe, the United States and Russia launched the NEO Shield project in Berlin last week. Over the next three-and-a-half years, the group will investigate three specific techniques for deflecting near-Earth objects away from the planet.
An asteroid, comet or the like is generally considered a near-earth object if it passes no further than one-third the distance between the Earth and the sun. Their size can vary.
At the end of the research period, Harris told Deutsche Welle the consortium will likely seek further funding to test the two best techniques in outer space.
"We want to prove that the human race is in a position, is technically capable, of deflecting a dangerous asteroid," he said.
Ingenious techniques
The techniques NEO Shield is developing are nothing if not ingenious. In one method, called the "gravity tractor," a space shuttle would fly alongside the incoming near-Earth object but keep from touching it.
Since everything has its own gravitational field, the idea is that the spaceship's would push the near-Earth object onto a trajectory away from our planet.
Another technique only seems more basic: sending a ship directly at the near-Earth object to push it off its path. But Harris pointed out, "you need to have a very sophisticated guidance control system to make sure you hit the asteroid on the right place," which in turn requires elaborate calculations for the object's center of mass.
Similar considerations would go into the third method NEO Shield is studying, changing a near-Earth object's trajectory with an explosion.
Harris mentioned several other techniques his team has discussed. Those included deploying a huge mirror to outer space to reflect the sun's rays onto a near-earth object, or even painting the object so it absorbs more light.
While Harris said sunlight can change an object's orbit, he added that such methods would take decades to execute.
Over-worrying at work?
NEO Shield was the product of a European Commission call for proposals to protect against near-earth objects last year. The EC is spending 4 million euros ($5.1 million) on the project, with another 1.8 million euros coming from the project members themselves.
But how likely is the Earth to get damaged by an asteroid again?
"We know the next asteroid is on the way," Harris said, "We just don't know when. It could be in a few years' time, it could be in a thousand years' time"
US space agency NASA has located more than one million near-Earth objects that are more than 40 meters in diameter.
But Robert Massey, an astrophysicist at the Royal Astronomical Society in London, said the chances a near-Earth object will hit the planet in the near future are low, and few objects would be big enough to cause any damage if they did.
"Is it the most urgent hazard?" he told Deutsche Welle. "Absolutely not. But just as we design buildings to protect against earthquakes, it can also be helpful to look into this."
Author: Shant Shahrigian
Editor: Cyrus Farivar