NASA scientists at the agency's Jet Propulsion Laboratory in Pasadena, Calif., effectively have ruled out the possibility the asteroid Aphophis will impact Earth during a close flyby in 2036. The scientists used updated information obtained by NASA-supported telescopes in 2011 and 2012, as well as new data from the time leading up to Aphophis' distant Earth flyby.

Discovered in 2004, the asteroid, which is the size of three-and-a-half football fields, gathered the immediate attention of space scientists and the media when initial calculations of its orbit indicated a 2.7 percent possibility of an Earth impact during a close flyby in 2029.

Data discovered during a search of old astronomical images provided the additional information required to rule out the 2029 impact scenario, but a remote possibility of one in 2036 remained - until yesterday.

"With the new data provided by the Magdalena Ridge [New Mexico Institute of Mining and Technology] and the Pan-STARRS [Univ. of Hawaii] optical observatories, along with very recent data provided by the Goldstone Solar System Radar, we have effectively ruled out the possibility of an Earth impact by Apophis in 2036," said Don Yeomans, manager of NASA's Near-Earth Object Program Office at JPL.

"The impact odds as they stand now are less than one in a million, which makes us comfortable saying we can effectively rule out an Earth impact in 2036. Our interest in asteroid Apophis will essentially be for its scientific interest for the foreseeable future."

The April 13, 2029, flyby of asteroid Apophis will be one for the record books. On that date, Apophis will become the closest flyby of an asteroid of its size when it comes no closer than 19,400 miles (31,300 kilometers) above Earth's surface.

"But much sooner, a closer approach by a lesser-known asteroid is going to occur in the middle of next month when a 40-meter-sized asteroid, 2012 DA14, flies safely past Earth's surface at about 17,200 miles," said Yeomans.

"With new telescopes coming online, the upgrade of existing telescopes and the continued refinement of our orbital determination process, there's never a dull moment working on near-Earth objects."

NASA detects and tracks asteroids and comets passing close to Earth using both ground and space-based telescopes. The Near-Earth Object Observations Program, commonly called "Spaceguard," discovers these objects, characterizes a subset of them and plots their orbits to determine if any could be potentially hazardous to our planet.