Thursday, January 03, 2008

Mars in the crosshairs

Will Mars be hit by an asteroid later this month? The answer remains a resounding "maybe."

Just a couple of posts ago, I talked about how it looked like an asteroid may hit Mars. The chances were low, just one in 350. Then, late December observations of the asteroid allowed better predictions to be made. The probability went up to nearly 1-in-25 (a 4% chance) before dropping slightly to a 1-in-30 chance. More observations in the coming weeks will help to refine the orbit. But we may not know for sure until we look for a new crater after January 30.

Mars will still probably survive unscathed, though, as I said before, we would learn a lot about asteroid collisions from a hit.

However, this is also a good learning experience for the process astronomers would go through if we saw an asteroid headed for the Earth. The odds of a collision often cannot be calculated as fast as we might like. It takes years of observations to pin down an asteroid orbit to the 8000 mile precision we need to predict an Earth collision.

An example is the asteroid 99942 Apophis. At one point, this asteroid had 1-in-300 chance of hitting the Earth in 2029 and 2036; two years of observing were needed to lower that chance to 1-in-45,000 for 2036 (and virtually zero for 2029). The Wikipedia page on this object gives a timeline of these odds.

Now, imagine if, instead of the date being 21 years away, but just a few months, how much panic there may have been, especially with the odds changing rapidly. This scenario worries us. Part of the problem is that we still don't know how to deflect an asteroid, and, if we make a mistake, we can cause an asteroid that was going to miss us (even a miss by 200 miles is still a miss!) to impact the Earth.

The best remedy for this is to keep on studying asteroids, their compositions, how they are constructed. Also, we need to keep looking for these asteroids. The further in advance we find an inbound asteroid, the more options we have, and the less panic we need to cause.

1 comment:

  1. I recall Comet Shoemaker-Levy into
    Jupiter, circa 1994, so the effort
    seems worthwhile!