typodupeerror

## NASA Downgrades Asteroid-Earth Collision Risk244

coondoggie writes "NASA scientists have recalculated the path of a large asteroid known as Apophis and now say it has only a very slim chance of banging into Earth.. The Apophis asteroid is approximately the size of two-and-a-half football fields, and updated computational techniques and newly available data indicate the probability of an Earth encounter on April 13, 2036 for Apophis has dropped from one-in-45,000 to about four-in-a million, NASA stated."
This discussion has been archived. No new comments can be posted.

## NASA Downgrades Asteroid-Earth Collision Risk

• #### is this too early to predict path ? (Score:1, Interesting)

on Wednesday October 07, 2009 @03:57PM (#29674489)
Given that it is supposed to hit in 2036, isn't it too early to be able make accurate predictions ? I mean, I am sure these predicted probabilities will keep changing as it gets closer ( assuming its headed in our direction right now ). I mean, who knows if the path of the asteroid may deviate a little bit due to gravitational pull of different planets/stars etc
• #### Re:Million-to-one chance (Score:3, Interesting)

<slashdotNO@SPAMspad.co.uk> on Wednesday October 07, 2009 @04:15PM (#29674719) Homepage

Million-to-one chances crop up 9 times out of 10.

• #### Re:is this too early to predict path ? (Score:4, Interesting)

on Wednesday October 07, 2009 @04:29PM (#29674845) Homepage

I mean, who knows if the path of the asteroid may deviate a little bit due to gravitational pull of different planets/stars etc.

Well they're pretty certain that it will deviate due to the variety of forces on it, which is exactly why the result is given as a probability, rather than a "will hit" or "will miss by X miles". It's also why the probability changed with further observation. Conditional probability is basically serving as a stand-in for what we don't know and the fact that we can't solve N-body gravitational problems. The more we know about the asteroid's trajectory, the more we can say about it's potential future paths and the likely hood of it hitting earth. At the end of the day (or the planet), it will either be nudged onto a path that will impact us or it won't, but right now it looks unlikely that it'll happen.

• #### NASA and risk... (Score:4, Interesting)

on Wednesday October 07, 2009 @05:08PM (#29675265) Journal

Taken from: http://en.wikipedia.org/wiki/Rogers_Commission [wikipedia.org]

"Feynman was clearly disturbed by the fact that NASA management not only misunderstood this concept, but in fact inverted it by using a term denoting an extra level of safety to describe a part that was actually defective and unsafe. Feynman continued to investigate the lack of communication between NASA's management and its engineers, and was struck by management's claim that the risk of catastrophic malfunction on the shuttle was 1 in 10^5; i.e., 1 in 100,000. Feynman immediately realized that this claim was risible on its face; as he described, this assessment of risk would entail that NASA could expect to launch a shuttle every day for the next 274 years without an accident."

Well, it has nothing to do with the topic, but I wouldn't trust a statement "four-in-a million" made by NASA... ;-)
There is no guarantee for a secure life on this planet. Asteroid impacts are a part of the nature, so everybody should be aware of those risks...

• #### Re:How useful is this, really? (Score:4, Interesting)

on Wednesday October 07, 2009 @05:31PM (#29675473)

Certainty is a funny word, but basically, the closer it gets the more confident you are in your prediction because small errors grow to large errors over time.

I would say, without significant funding you'd know for certain in the lead up to the 2029 close approach. During this event, the asteroid will pass within the geostationary satellite belt, and has the potential (1 in 250,000 now) to pass through a 'gravitational keyhole' that corresponds with a return impact trajectory. Note that the likelihood of impact in 2029 is zero (i.e. the 6-sigma boundaries of trajectory estimates are very far from the Earth).

Unfortunately, if you don't do something about it well before 2029, its unlikely you could do anything short of an Apollo-class-plus (Bruce Willis-class?) mission, in terms of funding, uncertainty, and national effort, to stop it. Put simply, its much easier to push the asteroid a kilometer (out of a keyhole) than it is to push it 3000 kilometers, but you have to do it earlier.

If you wanted to do very precise tracking to know if (and where) it was going to impact without waiting for the close approaches, you can do some of it with simply more observations with larger telescopes, and more ground-based radio ranging. However, you're going to get much better results (an order of magnitude) if you send a spacecraft out with a proper beacon. Two or three months in 2021 with this kind of tracking would give you 3-sigma (99%) reliability if it is to impact, and ascertain that it was not if it is not going to. A year of this tracking would tell you where exactly it was going to hit, within about 100km.

Of course, if you're already out there, its not too much more expensive to add the equipment to do a gravity tractor and move it away from a keyhole, since by 2022 it would be very difficult and very expensive to get a mitigation mission put together in time. A combined exploration and mitigation mission is estimated to cost about \$350M, and in addition to improving knowledge about the unlikely but potentially imminent threat, would make it much easier to deal with future threats and contribute a lot to our understanding of near Earth asteroids in general. A pure exploration mission might be able to shave off \$25M -- the only extra equipment is some Hall thrusters and a longer lifetime. I personally think there is political will for it at relatively low cost (Discovery-class mission), and scientific benefits beyond the mitigation of an admittedly small risk.

(Full Disclosure: Most of these numbers are pulled from a mission proposal I'm currently working on. The details aren't officially published yet, although they are being presented at a conference next week.)

Were there fewer fools, knaves would starve. - Anonymous

Working...