“In the unlikely event of an impact..”

When I noted the asteroid 2007 WD5 previously the impact probability with Mars was a 1 in 75 chance, described by NASA astronomer Steve Chesley as “a very high impact probability for what we’re used to dealing with”. Yesterday NASA reported that the discovery of more data on the asteroid’s orbit has allowed them to refine the orbit and the uncertainties. It’s still more likely to miss than to hit, but the chances have gone up to 1 in 25 (an increase from a 1.3% to a 3.9% chance of impact). From the NASA press release

“Pre-discovery observations of asteroid 2007 WD5, taken on November 8, 2007 have allowed its orbit to be refined and the uncertainties for the late January Mars encounter have been improved. The impact probability resulting from the recent orbit refinement has increased to a surprising 3.9% (about 1 in 25 odds). The uncertainty region during the Mars encounter now extends over 400,000 km along a very narrow ellipsoid that is only 600 km wide. Since the uncertainty region intersects Mars itself, a Mars impact is still possible. However, the most likely scenario is that additional observations of the asteroid will allow the uncertainty region to shrink so that a Mars impact is ruled out. In the unlikely event of an impact, the time would be 2008 January 30 at 10:56 UT (2:56 a.m. PST) with an uncertainty of a few minutes.”

Current position of 2007 WD5