A group that monitors Near Earth Asteroids is urging NASA to develop a strategy for dealing with a recently discovered asteroid that could strike Earth in 2036.
The U.S. space agency is being prodded by a group of astronauts, scientists and other technical specialists who are uneasy about the current lack of action to protect the Earth from potential impacts with near Earth objects (NEOs).
The object was found last year through the efforts of NASA’s Spaceguard Survey. In 1998 NASA formally initiated the Spaceguard Survey by adopting the objective of finding 90 percent of the near Earth asteroids larger than one kilometer in diameter before the end of 2008.
Asteroid 99942 Apophis — first labeled as 2004 MN4 — is estimated to be roughly 320 meters in diameter. Were it to strike Earth, it would not set off global havoc but would generate significant local or regional damage, experts say.
Asteroid watchers are worried about the exceptionally close flyby of Earth that Apophis is expected to make April 13, 2029. the encounter will be so close in fact, the space rock will be naked-eye visible as it darts by. Experts canno t rule out at this time the possibility that Apophis may pass through what is known as a gravitational keyhole — a spot that alters the asteroid’s trajectory as it zips by our planet. That change might put it on a trajectory to strike the into Earth seven years later.
A group known as the B612 Foundation, chaired by Russell Schweickart, a former Apollo astronaut, asked NASA to conduct an analysis that included the possibility of placing an active radio transponder on the object. Doing so at a fairly early date would yield the requisite orbital accuracy of the asteroid as it sped through space.
In a June 6 letter to NASA Administrator Michael Griffin, Schweickart, on behalf of the B612 Foundation, called for support in “resolving an issue of critical importance” — namely whether a scientific mission should be launched to asteroid Apophis in the near term.
Such a probe if dispatched, Schweickart stated, would provide knowledge of the asteroid’s orbit in time to initiate a deflection mission in the unlikely event one should be required. A spacecraft mission to Apophis would augment tracking of the object from the ground and carry out a number of scientific duties, Schweickart said in the letter to Griffin.
NASA provided a formal response in an Oct. 12 letter from Mary Cleave, NASA associate administrator for science, which included a detailed analysis by Steven Chesley of NASA’S Near Earth Object Program Office at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif.
“The key conclusion to be taken from this analysis,” Cleave said , “is that aggressive (i.e., more expensive) action can reasonably be delayed until after the 2013 observing opportunity. For Apophis, the 16 years available after 2013 are sufficient to recognize and respond to any hazard that still exists after that time.”
Cleave noted in the letter that while Apophis “is an object whose motion we will continue to monitor closely in the coming years, we conclude a space mission to this object based solely on any perceived collision hazard is not warranted at this time.”
Cleave, however, did not rule out the possibility that someone might bid for a Discovery-class, low-cost mission that could be sent to Apophis, “based on purely scientific arguments,” she said.
“Indeed, the asteroid’s orbit is particularly attractive for spacecraft rendezvous, and the extraordinary close encounter in April 2029 provides a unique opportunity to investigate a number of scientific NEO issues,” Cleave said in the letter.
Asteroid Apophis and the discussions it has sparked are welcome , observed David Morrison, a space scientist and asteroid specialist at NASA’s Ames Research Center, situated in Silicon Valley, Calif .”I am pleased that this dialog is taking place,” Morrison said. “This is the first time that serious possibilities for dealing with a real but low-probability future impact have been discussed in a technically professional way, rather than receiving the ‘Hollywood treatment.’”
Morrison said that he considers it remarkable that the Spaceguard Survey has reached the level of maturity where such an asteroid could not only be found, but its orbit understood well enough to deal with “keyholes” and other subtleties. “Apophis represents for me a symbol of the coming of age of Spaceguard and of asteroid impact studies in general,” he said.
The possibility of Apophis hitting Earth on April 13, 2036, is real, Morrison said, even if the probabilities now seem to be very small. “These probabilities represent uncertainties in our knowledge of the orbit, not a failure of the science.”
But whether the asteroid will strike Earth or not, Morrison concluded, the challenge is to resolve which case is correct. “With more observations over a longer time span, we will be able to tie this down.”
