Asteroid Will Make Close Pass To Earth

The Bad Astronomer writes "News is starting to spread about a small 45-meter-wide asteroid called 2012 DA14 that will make a close pass to Earth on February 15, 2013. However, some of these articles are claiming it has 'a good chance' of impacting the Earth. This is simply incorrect; the odds of an impact next year are essentially zero. Farther in the future the odds are unclear; another near pass may occur in 2020, but right now the uncertainties in the asteroid's orbit are too large to know much about that. More observations of DA14 are being made, and we should have better information about future encounters soon."

Comments

JPL impact risk table

[Anonymous Coward]

TFA contains a link to an predicted impact table of DA14 with earth, going some 50 years into the future. The likelihood of each impact is rather small, and the cumulative probability of any impact is computed as 2.2e-04 (about 1 in 5000 - not alarming, but not exactly negligible IMO).

Here's what I don't understand: the first entry in the chart, corresponding to the next risk event, is in the year 2020. What happened to Feb 2013?

Re:JPL impact risk table

[jaa101]

Since we can predict the next (2013) close approach very accurately we're very confident it will be a miss. Therefore that approach doesn't rate a mention in the table.

The trouble comes in that, while we know the 2013 approach distance will be greater than 0km from the surface (>6400km from the centre) there's still some uncertainty. The earth is massive and the close approach will cause a relatively large change in the orbit of DA14. The size of the change is inversely proportional to the square of the approach distance. Thus even a small uncertainty for 2013 results in a large uncertainty for subsequent approaches. Celestial billiards at work.

Re:45 meters?

[Solandri]

The asteroid which made Meteor Crater in Arizona is estimated to have been about 50 meters across. About half of it is thought to have burned up before impact.

Re:Good riddance

[buchner.johannes]

Touching/Landing on asteroids is difficult because they have very complicated structures and rotations. The best way to deflect an asteroid is not by nukes or what you suggest, but by spraying it white (solar radiation pressure) or parking a mass (e.g. 1t) with a ion drive next to it.

http://www.physorg.com/news/2011-11-deflect-asteroid.html
https://en.wikipedia.org/wiki/Asteroid-impact_avoidance#Collision_avoidance_strategies