A giant asteroid has a chance—albeit a very tiny one—of colliding with the Earth in 2068, a new analysis of the object shows.
Scientists say they have measured, for the first time, how a phenomenon known as "Yarkovsky acceleration" is affecting the orbit of the space rock—dubbed "99942 Apophis" after an ancient Egyptian "god of chaos"—as it circles the sun, according to research presented at the 2020 virtual meeting of the Division for Planetary Sciences of the American Astronomical Society.
Astronomers first spotted Apophis in June 2004 in observations conducted by the Kitt Peak National Observatory in Arizona.
The object is estimated to measure more than 1,100 feet in diameter, which is nearly as tall as the Empire State Building in New York City.
Since it was discovered, scientists have been closely monitoring the object, which is scheduled to make a number of close approaches to the Earth over the course of the next century and beyond.
Initially, it looked as if the asteroid might have an uncomfortably high chance—2.7 percent—of crashing into the Earth in 2029, or perhaps in 2036.
Subsequent observations of the space rock's trajectory have revealed that there is now no chance of this happening, although Apophis will still pass close enough to the Earth on April 13, 2029 that it will be visible with the naked eye, even coming closer to our planet than some orbiting spacecraft.
"We have known for some time that an impact with Earth is not possible during the 2029 close approach," Dave Tholen, an author of the latest research from the University of Hawaiʻi Institute for Astronomy, who was part of the team that first spotted Apophis, said in a statement.
Observations also suggested that Apophis' close approach in 2068 would also likely not result in an impact.
But Tholen said observations conducted by the Subaru telescope on Mauna Kea, Hawai'i earlier this year revealed how "the Yarkovsky effect" was shifting the asteroid's orbit around 550 feet per yer away from its standard trajectory, which is "enough to keep the 2068 impact scenario in play."
The Yarkovsky effect refers to a small but significant force that influences the orbits of asteroids and similar bodies in space. When these objects are heated by sunlight, they eventually release some of this energy, which creates a tiny amount of thrust.
Over long periods of time, this effect can lead to significant changes in the path of these objects. And in the case of Apohis, the effect influences the probability of an impact with the Earth in 2068.
"With Yarkovsky taken into account, the 2068 impact scenario is still in play. Small, but non-zero," Tholen told Gizmodo.
NASA's Sentry Risk Table currently lists Apophis as the third highest threat to our planet among known near-Earth objects, with a one in 150,000 chance that there could be an impact on April 12, 2068, although this figure does not take the latest findings into account.
The researchers say the odds of the asteroid striking Earth will likely change over time as more observations are made. In any case, astronomers will know well before 2068 if there is going to be any chance of an impact.
If the asteroid were to strike the collide with the Earth, "it could cause continent-scale devastation, but not a global extinction," Davide Farnocchia, another author of the research from NASA's Jet Propulsion Laboratory, previously told Newsweek.
An impact involving an object of this size only occurs on Earth roughly once ever 80,000 years, according to a calculator created by researchers from Imperial College London in the U.K. and Purdue University.
