Discovery date 20 November 2007 Semi-major axis 2.4600 AU (368.01 Gm) Orbital period 1,479 days Inclination 2.4276° Discoverer Andrea Boattini | Aphelion 3.9289 AU (587.76 Gm) Eccentricity 0.59711 Discovered 20 November 2007 Argument of perihelion 309.622° Asteroid group Apollo asteroid | |
Discovered by Mount Lemmon Survey
Andrea Boattini
(unofficial credits) Minor planet category NEO · Apollo
Mars-crosser Similar 5261 Eureka, Solar System, C/2013 A1, 2007 TU24, Deimos | ||
Asteroid 2007 wd5 targets mars for 2008 impact
2007 WD5 is an Apollo asteroid some 50 m (160 ft) in diameter and a Mars-crosser asteroid first observed on November 20, 2007, by Andrea Boattini of the Catalina Sky Survey. 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 January 30, 2008. However, by January 9, 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. 2007 WD5 most likely passed Mars at a distance of 6.5 Mars radii. 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).
Contents
Asteroid 2007 wd5
Discovery
The asteroid was discovered on November 20, 2007 by Andrea Boattini of the NASA-funded Catalina Sky Survey on Mount Lemmon, near Tucson, Arizona, United States, using a 1.5-meter telescope. It was discovered in the constellation Taurus at an apparent magnitude of +20. This is about 400,000 times fainter than most people can see with the naked eye on a dark night far from city lights. It was discovered nineteen days after passing near the Earth. By the time it arrived at Mars it had an apparent magnitude of roughly +26 and therefore appeared over 100x fainter than at the time of discovery.
Timeline of observations and events
This trend of increasing probability of impact followed by a dramatic decrease is typical as uncertainties are gradually reduced. In December 2004, a similar trend was observed with 99942 Apophis where the predicted probability of impact with Earth in 2029 at one point reached as high as 2.7%.
Estimates of resulting impact
If the asteroid had collided with Mars, it would have hit with a velocity of about 13.5 km/s (8.4 miles per second), and would have produced an explosion equivalent to about 3 megatons of TNT. 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. A crater this size would be equal to the size of the Meteor Crater in Arizona, United States. NASA officials say if it had hit Mars, it would have done so north of the location of the Opportunity rover.
2007 WD5 is roughly the size of the cometary object that caused the Tunguska event in 1908, in remote central Siberia, Russia. Due to the Earth's greater gravity, an impact with the power of Tunguska is expected to occur once every few hundred years. Since Mars has only 1/10 the mass to attract objects, these types of impacts occur roughly every one thousand years on Mars.
Future encounters
In July 2003, the asteroid passed within 0.012 AU of Mars. The exact fate of 2007 WD5 following the January 2008 Mars encounter is unknown although it likely passed Mars at a distance of 6.5 Mars radii. Mars, unlike Jupiter, is not big enough to eject the asteroid from the Solar System, however, the gravitation effect from the encounter on the asteroid's trajectory is uncertain and the asteroid is currently considered 'lost'. Assuming 2007 WD5 passed Mars safely, its low inclination to the ecliptic of only 2.3 degrees and high eccentricity of 0.6 could cause it to swing close to Mars or Earth for years or decades into the future.