The Apophis asteroid is approximately the size of two-and-a-half football fields and updated computational techniques and newly available data indicate the probability of an Earth encounter on April 13, 2036, for Apophis has dropped from one-in-45,000 to about four-in-a million, NASA stated.
Initially, Apophis was thought to have a 2.7% chance of impacting Earth in 2029. Additional observations of the asteroid ruled out any possibility of an impact in 2029.
The new data were documented by near-Earth object scientists Steve Chesley and Paul Chodas at NASA's Jet Propulsion Laboratory in Pasadena, Calif. They will present their updated findings at a meeting of the American Astronomical Society's Division for Planetary Sciences in Puerto Rico this week.
The recalculated trajectory came from scientists at the University of Hawaii's Institute for Astronomy in Manoa and its 88-inch telescope, located near the summit of Mauna Kea.
The information provided a more accurate glimpse of Apophis' orbit well into the latter part of this century. Among the findings is another close encounter by the asteroid with Earth in 2068 with chance of impact currently at approximately three-in-a-million. As with earlier orbital estimates where Earth impacts in 2029 and 2036 could not initially be ruled out due to the need for additional data, it is expected that the 2068 encounter will diminish in probability as more information about Apophis is acquired, NASA said.
NASA detects and tracks asteroids and comets passing close to Earth through its Near Earth-Object Observations Program or "Spaceguard." The program has been in the news lately as a National Academy of Sciences report said that while the space agency is tasked with watching out for huge chunks of space rocks that could smash into the earth, it has been denied the money to actually do the job.
The problem is that while Congress mandated four years ago that NASA detect and track 90% of space rocks known as near earth objects (NEO) 140 kilometer in diameter or larger, it has not authorized any funds to build additional observatories, either in space or on the ground, to help NASA achieve its goals, according to a wide-ranging interim report on the topic released by the National Academy of Sciences this week.
The report notes that NASA has managed to accomplish some of the killer asteroids mandate with existing telescopes but with over 6,000 known objects and countless others the task is relentless. NASA does carry out the "Spaceguard Survey" to find NEOs greater than 1 kilometer in diameter, and this program is currently budgeted at US$4.1 million per year for FY 2006 through FY 2012.
The report notes that United States is the only country that currently has an operating survey/detection program for discovering near-Earth objects; Canada and Germany are both building spacecraft that may contribute to the discovery of near-Earth objects. However, neither mission will detect fainter or smaller objects than ground-based telescopes.
The report goes on to state: Imminent impacts (such as those with very short warning times of hours or weeks) may require an improvement in current discovery capabilities. Existing surveys are not designed for this purpose; they are designed to discover more-distant NEOs and to provide years of advance notice for possible impacts. In the past, objects with short warning times have been discovered serendipitously as part of surveys having different objectives. Search strategies for discovering imminent impacts need to be considered, and current surveys may need to be changed.