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An artist's impression of a generic asteroid. ESA-Science Office, ESA Standard LicenceNASA has identified an asteroid with a more than 1 percent chance of striking Earth in December 2032, per a statement released by the agency this week. While the identification has triggered international planetary defense measures, experts say that further observations of the asteroid might drop the impact probability down to zero.Most likely this one will pass by harmlessly, Colin Snodgrass, an astronomer at the University of Edinburgh in Scotland, tells the Guardians Ian Sample. It just deserves a little more attention with telescopes until we can confirm that. The longer we follow its orbit, the more accurate our future predictions of its trajectory become.The NASA-fundedAsteroid Terrestrial-impact Last Alert System (ATLAS) station in Chile first reported the asteroid, called 2024 YR4, on December 27, 2024. Within a few days it had risen to the top of NASAs Sentry risk table and the European Space Agencys near-Earth object Risk List, where it currently has a 1.6 percent chance, or 1-in-63 odds, of impacting Earth in about eight years. That also means it has a 98.4 percent chance of zooming by without causing any damage.Asteroid 2024 YR4 is estimated to have a diameter of around 130 to 300 feet, which is not remotely large enough to be civilization-ending, like the space rock that nearly wiped out the dinosaurs. Its more comparable to the 1908 Tunguska impactor, which flattened an 830-square-mile area of forest in Siberia. An asteroid of this size still has the potential to destroy a major city or cause a massive tsunami, but in the unlikely case of a predicted collision, authorities would have time to plan necessary evacuations.However, scientists infer the size of asteroids from the amount of light they reflect, which also depends on their composition. That means astronomers have some inherent uncertainty in their measurement of this asteroids diameter.If the asteroid has a darker surface, that number is too small; if it has a more reflective surface, that number is too high, David Rankin, an engineer at the Catalina Sky Survey, tells Space.coms Robert Lea. Scientists will be able to more accurately study all aspects of the asteroid, and thus refine their predictions, during its next flyby in 2028.The first step in the planetary defense response is to trigger further observations, explains Snodgrass to the Guardian. If these observations dont rule out an impact, the next steps will be more detailed characterization measurements using telescopes and discussion of what space agencies could do in terms of more detailed reconnaissance and eventually mitigation missions. This asteroid is of the scale that a mission like DART could be effective, if required, so we have the technology, and it has been tested.NASAs Double Asteroid Redirection Test, or DART, successfully changed the course of an asteroid by slamming a spacecraft into it in 2022, demonstrating the methodologys potential to redirect future Earth-threatening objects.The international systems were putting in place to find, track and characterizeand, if it comes to it, mitigate the impacts ofhazardous asteroids and comets are working as intended, Andy Rivkin, an astronomer and planetary defense researcher at the Johns Hopkins Applied Physics Laboratory, tells the New York Times Robin George Andrews.Asteroid 2024 YR4 is currently ranked at level three on NASAs Torino Impact Hazard Scale, meaning it merits attention by astronomers. The highest ranking an asteroid has ever reached on the scale is four, briefly achieved by asteroid Apophis in 2004 before further observations downgraded it back to zero. It seems likely that this will also happen with asteroid 2024 YR4.We expect the impact probability to go to zero rather than 100 percent, Rivkin says to the New York Times. But it may take a few years before we get the data to show that.Get the latest stories in your inbox every weekday.Filed Under: Asteroids, Astronomers, Astronomy, NASA, Outer Space
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