Mars Impact Seems Less Likely

We have updated the orbit of 2007 WD5 using new observations from the 3.5-meter telescope at the Calar Alto Observatory in Spain. This update also incorporates refinements to the Sloan precovery observations mentioned previously. While the best estimate of close approach distance remains steady at about 30,000 km, the uncertainty in position at the close approach has decreased by a factor of three. As a result, the impact probability estimate has fallen to 2.5%, or 1-in-40 odds. If the estimated miss distance remains stable in future updates, the impact probability will continue to fall as continuing observations further constrain the uncertainties.

Updated Uncertainty Region for 2007 WD5 at encounter with Mars, shown as white dots. The thin white line is the orbit of Mars. The blue line traces the motion of the center of the uncertainty region, which is the most likely position of the asteroid.

Related:

• New Observations Slightly Decrease Mars Impact Probability (NASA - January 2, 2008)
• Mars Impact Probability Increases to 4 Percent (NASA - December 28, 2007)
• Recently Discovered Asteroid Could Hit Mars in January (2007 WD5) (NASA - December 21, 2007)
• Orbit Diagram for Asteroid 2007 WD5
• Astronomers Monitor Asteroid to Pass Near Mars (NASA - December 21, 2007)
• JPL podcast: Is an Asteroid Heading Toward Mars? (JPL - December 21, 2007)
• Catalina Sky Survey Discovers Space Rock That Could Hit Mars (University of Arizona - December 21, 2007)