2007 WD5

Early observations of 2007 WD5 caused excitement amongst the scientific community when it was estimated as having as high as a 1 in 25 chance of colliding with Mars on 30 January 2008.

[6] However, by 9 January 2008, additional observations allowed NASA's Near Earth Object Program (NEOP) to reduce the uncertainty region resulting in only a 1-in-10,000 chance of impact.

Due to this relatively small distance and the uncertainty level of the prior observations, the gravitational effects of Mars on its trajectory are unknown and, according to Steven Chesley of NASA's Jet Propulsion Laboratory Near-Earth Object program, 2007 WD5 is currently considered 'lost' (see lost asteroids).

[8] The asteroid was discovered on 20 November 2007 by Andrea Boattini[9] of the NASA-funded Catalina Sky Survey on Mount Lemmon, near Tucson, Arizona, United States, using a 1.5-meter telescope.

[4] Due to the thin atmosphere of Mars, it was predicted that the asteroid would have reached the surface intact and blasted out a crater approximately 0.8 km (0.5 mi) in diameter.

NASA Animation showing the motion of the uncertainty region of 2007 WD5 as it approaches Mars. 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. Orbital data as known on 21 December 2007
Track of asteroid 2007 WD 5 over Mars (NASA/JPL)