Last week, asteroid 2004 MN4 had been given a small chance of impacting Earth, based on observations in June and again this month. Astronomers then began independent efforts to find earlier observations of the asteroid.
The Spacewatch Observatory near Tucson, Ariz., found faint pictures of the asteroid in archival images dating to March 15, the Near Earth Object Program Office, located at the Jet Propulsion Laboratory, said in a statement on its Web site this week.
The pictures from March allowed scientists to refine the asteroid's projected trajectory, and "an Earth impact on 13 April 2029 can now be ruled out," the program office said.
Scientists also ruled out an impact with the moon.
Spacewatch is associated with the University of Arizona's Lunar and Planetary Observatory.