Bumping asteroid from Earth could cost more than $80B
Chances of a direct hit might be low, but as one expert put it, `not if you're betting the planet'
The head of Russia's space agency has called for a massive planetary effort to deflect a massive asteroid as it skips by Earth in 2029.
"People's lives are at stake," Anatoly Perminov told Voice of Russia radio Wednesday. "We should pay several hundred million dollars and build a system that would allow us to prevent a collision, rather than sit and wait for it to happen and kill hundreds of thousands of people."
Perminov said Russia will consider building a spacecraft designed to nudge the Apophis asteroid away from the Earth, and invited NASA, the European Space Agency and the Chinese space agency to join in.
The Apophis asteroid, around three football fields in size, was first spotted heading toward Earth five years ago. It was suggested then there was a 2.7 per cent chance it would strike our planet in 2029. That alarming estimate has been seriously downgraded since, but it continues to hold the attention of expert observers.
Apophis will first pass us at close range in just under 20 years. It may almost graze the Earth, missing by only 30,000 kilometres, less than the distance between Earth and the moon. At this point, astronomers have ruled out the possibility that it will hit us.
However, there is a very small chance that it will pass through a 600 metre-wide "gravitational keyhole" as it swings by. That would alter its course and cause it to slingshot back and hit the Earth in 2036. New NASA calculations released in October rate the chance of impact during the second pass at 1 in 250,000.
That still doesn't sound terribly alarming, but as Dr. William Ailor, of California's Aerospace Corporation, said Wednesday, "That's a pretty high probability if you're betting the planet."
In April, Ailor chaired the biannual Planetary Defense Conference of the world's leading asteroid experts.
"There are still issues around how great does the risk have to be before you start planning a (defence) mission like this. But ultimately, everyone agrees that we will have to do this sooner or later," Ailor said.
Donald K. Yeomans, manager of NASA's Near-Earth Object Program Office, says the time to make a decision on Apophis will be in late 2012 and early 2013, when it makes another close approach, within about 14 million kilometres of Earth.
"The additional optical and radar data taken then will almost certainly remove any possibility of an Earth collision in April 2036. To my mind it would make sense to wait until 2013, refine the orbit and in the very unlikely event that the impact probability increases, then begin planning possible deflection options," Yeomans said.
"While Apophis is almost certainly not a problem, I am encouraged that the Russian science community is willing to study the various deflection options that would be available in the event of a future Earth-threatening encounter by an asteroid."
A variety of deflection methods have been suggested in the past: gravitational tractors; landing a manned mission on Apophis; knocking it off target by ramming it or striking it with nuclear weapons. There is no broad consensus on what might work best.
"There's also the question of how you design the `campaign' to attack the asteroid. You'd probably have to launch multiple vehicles, in case some failed," Ailor said.
Five years ago, Ailor said, the Aerospace Corp. ballparked the cost of such a mission at $80 billion (U.S.). NASA's current annual budget is a little over $17 billion. Perminov, sounding less than expert on the grasp of details, got the year of impact wrong (2032), couldn't cite the latest estimates accurately and seriously underestimated the potential cost. But he's right about the risk.
Ailor points out that the 1908 asteroid that exploded over Tunguska in Siberia was only 30 metres across. It devastated more than 2,000 square kilometres of forest. Apophis is 270 metres in diameter.
What if it hit the Earth directly?
"That'd be a very bad day," Ailor said.
"Probably not the end of all life as we know it. But a bad day."
No comments:
Post a Comment