Defending the Earth From a Doomsday Asteroid

[CaptinCrunch]

Scientists Discuss Ways to Avoid Hits From Space

By ANDREW BRIDGES, AP

GARDEN GROVE, Calif. (Feb. 23) - The asteroid believed to have wiped out dinosaurs 65 million years ago was rare but hardly unique, say scientists gathered to discuss ways of aggressively defending our planet from another such space rock, including by detonating nukes in space.



Asteroids capable of inflicting damage on a global scale hit the Earth roughly every million years, and we shouldn't dawdle in developing a method of deflecting them, say the scientists attending a four-day planetary defense conference in suburban Orange County.

Scientists have proposed a variety of strategies to nudge an asteroid off course. The list is the stuff of science fiction and includes using lasers, mirrors or atomic weapons launched from Earth.

Unlike any other type of natural hazard, an asteroid impact could kill billions of people. But it's also the only natural hazard that can be prevented, at least in principle, scientists said.

"It's a thing we know will happen sometime in our future so the responsible thing is for people to do something about it," said William Ailor, of The Aerospace Corp., which sponsored the conference with the American Institute of Aeronautics and Astronautics.

Astronomers estimate there are between 900 and 1,100 near-Earth asteroids one kilometer - about six-tenths of a mile - or larger in diameter. Of those, nearly 700 already have been discovered and cataloged.

It's not clear what sort of damage one of those rocks could cause were it to strike Earth, although destruction on a global scale is likely.

"We don't know what they would do, and we don't want to conduct a science experiment to find out," said David Morrison of NASA's Ames Research Center.

Rep. Dana Rohrabacher, R-Calif., introduced a bill this month to bolster NASA spending on the search for near-Earth asteroids 100 yards or more across.

Even something of that size, were it to strike, say, the Pacific Ocean, could generate a tsunami capable of destroying the major cities along the West Coast, Ailor said.

Early detection of an inbound asteroid could provide years to decades of warning - enough time to mount a mission to push it off course, Ailor said. Slowing an asteroid down by even a few inches a second could change its trajectory enough to prevent its ever crossing paths with the Earth.

The Earth moves in space the equivalent of its own diameter in just six minutes. So to move an Earth-bound asteroid off target, it would be enough to delay its arrival time by six minutes, allowing it to harmlessly sweep past, Morrison said.

[Aslkahuna]

is to detect these things long before they become a problem. The biggest problem has to deal with comets in retrograde Earth Crossing orbits (of which we know three) that approach us from Sunward at a high rate of speed. We might not even know of the existence of such an object until months at the earliest and would have no way of tracking the final approach since it would be invisible to us. It would be approaching us at speeds of up to 70 km/sec which would make the impact of a 1km diameter object equal in energy release to that of the largest fragment of SL-9 that hit Jupiter in 1994. That impact was quite noticeable to be sure. However, comets are generally larger in size than 1km. Although comets are fragile, one approaching at that speed (as opposed to the 12 km/sec approach of one coming from behind us) would transit the denser atmosphere of Earth in a bit over 2 seconds which would not be enough time for disruption. One coming in on a grazing low velocity track would probably airburst but the Tunguska event which released 20MT of energy in the airburst was only 0.1km in diameter and such an airbust over a city would have dire consequences.

Steve

[coriolis]

Here's a link to Nasa's site on this topic.
http://neo.jpl.nasa.gov/

It looks like we just dodged a bullet on Feb 17th when a small (30 meter) but speedy object came within 2.8 lunar distances of the earth!

The next very close miss will be on June 26 when a 1 km object will come within 5 lunar distances of earth.

click on the tab "orbit diagrams" and you can see a way cool animations of 578 objects. You can zoom in and out, change the speed, and rotate the axes so you can view the relative orbits at any angle.

Check it out!

[Aslkahuna]

actually been a few that have come between us and the Moon. Then there's Hermes which has been recently recovered. In the 1930's it came between us and the Moon and it's not a small object.

Steve