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According to CBS News, an asteroid, 2024 YR4, that is gaining notoriety for its potential to collide with Earth in 2032, saw its estimated impact probability fluctuate significantly this week.
Initially, NASA's Center for Near-Earth Object Studies estimated a roughly 3% chance of a collision on Tuesday, the highest probability ever assigned. However, additional analysis on Wednesday lowered those chances to approximately 1.5%, CBS News has learned.
The risks associated with this "city killer" category space rock have varied since its discovery last December. As CBS News reported, the near-Earth asteroid initially carried a 1% chance of impact when NASA and the European Space Agency (ESA) first announced its existence last month. Protocols mandate public notification when the odds of an asteroid strike reach this 1% threshold, a rare occurrence, reports Emily Mae Czachor.
CBS News reports that the highest estimate, from NASA's Jet Propulsion Laboratory, suggested a 3.1% chance of impact on December 22, 2032, during a period when the asteroid's orbit intersects Earth's path. The ESA's initial probability estimate was slightly lower, at 2.8%. Prior to the most recent change, NASA and the ESA had agreed on a probability closer to 2%, according to CBS News.
"However," NASA reported, as obtained by CBS News, "on Wednesday, Feb. 19, new data collected overnight reduced the impact probability to 1.5%." NASA also stated, "NASA expects the impact probability to continue to evolve as new observations of asteroid 2024 YR4 are made over the coming days and weeks."
Astronomers and researchers, speaking to CBS News, indicated that the probability could decrease to zero as more is learned about the asteroid, which will be closely observed by the James Webb Space Telescope before it becomes unobservable in April. Richard Moissl, head of the ESA's Planetary Defence Office, explained to CBS News last week that the fluctuating odds reflect evolving insights into the "uncertainty" area in space where the asteroid's path may lie.
"The size of the Earth -- which is inside the uncertainty area -- is compared to the entire area of the uncertainty of where the asteroid could be in that critical moment in time. This equated to about 1% when we reached this threshold for international awareness," Moissl told CBS News.
As CBS News reported, the uncertainty region has since shrunk, leading to a higher relative probability of Earth's presence within it. Moissl emphasised to CBS News that even a 3% chance of impact corresponds to a 97% chance of a miss, and that 2024 YR4 is unlikely to pose a threat.
"What will happen is, with our gaining knowledge, uncertainty will shrink further and further and further," he said. "And the expected case is that we will manage to shrink it so much that Earth is no longer inside this uncertainty region, and then the impact probability will drop to zero."
CBS News has learned that experts believe the probability of a crash will likely fall below 1% before April, when the asteroid's orbit takes it too far from Earth for observation. After that, 2024 YR4 will not be visible for four years.
While the probability of a collision could still rise moderately due to a "close flyby," Moissl told CBS News that "this is still no cause for alarm."
However, international space organisations are taking the risk seriously.
The asteroid, estimated to be 40 to 90 metres wide, could devastate a mid-sized city. If its actual size is closer to the larger end of the range, it could impact major metropolitan areas, according to CBS News.