Doomsday is not upon us yet. A day after announcing that an asteroid could collide with Earth in 2030 (ScienceNOW, 3 November), scientists with the International Astronomical Union (IAU) downgraded that chance to zero. New calculations show that asteroid 2000 SG344 will pass at least 4.4 million kilometers from Earth.
On Friday, IAU and NASA scientists at the Jet Propulsion Laboratory (JPL) in Pasadena gave the 30- to 70-meter-wide asteroid a one in 500 chance of smashing into Earth on 29 September 2030. The same day, scientists at the Catalina Sky Survey in Tucson, Arizona, identified 2000 SG344 on old images of the sky, allowing a more precise calculation of its orbit.
Ironically, the initial announcement was the first to follow a new set of IAU rules designed to avoid releasing false alarms. The guidelines state that the public should be notified of the potential danger of an asteroid within 72 hours of its discovery--enough time for scientists to verify that the danger is real, says David Morrison at NASA's Ames Research Center in Moffett Field, California.
In this case, the new policy didn't prevent the false alarm, says Paul Chodas, the JPL scientist who discovered the object, because other astronomers didn't start sifting through their archived data fast enough. "We need to refine the process and emphasize to observatories that we need to dig out the data quickly," Chodas says.
In the meantime, many scientists wonder whether the celestial threat really is an asteroid at all. The fact that it closely follows Earth's orbit suggests it may just be a booster rocket from an Apollo-era space flight that reflects as much light as a large, stony asteroid, Chodas says. A rocket would pose little or no threat, as it would burn up almost entirely in the atmosphere before smashing into Earth.