The American space agency (NASA) announced on Wednesday that the asteroid Bennu is set to come very close to Earth in 2135, reaching just half the distance between our planet and the Moon. However, they reassured that the likelihood of an impact by the year 2300 remains extremely low. This asteroid, discovered in 1999 and measuring 500 meters in diameter, is one of the known asteroids in our solar system that poses the greatest threat to Earth, according to NASA.
NASA's OSIRIS-REx spacecraft spent two years in orbit around Bennu, departing in May to collect samples gathered during a brief contact with the asteroid's surface, expected to arrive on Earth in 2023. This mission has allowed for close study of the asteroid and significantly improved predictions regarding its trajectory in the future.
Scientists concluded that by the year 2300, the probability of a collision with Earth does not exceed 0.057%. David Farnocchia, a researcher at NASA's Near Earth Object Studies, stated during a press conference, "In other words, this means there is a 99.94% chance that asteroid Bennu will not be on a collision course," thus "there is no need to panic."
But why can't they guarantee a 100% certainty? In September 2135, asteroid Bennu will pass very close to Earth. This will leave the possibility of crossing what is known as a "gravitational keyhole," an area that could slightly alter the asteroid's trajectory due to Earth's gravitational pull, potentially placing it on a collision course in the future. Prior to the OSIRIS-REx mission, there were 26 potential "keyholes" of a kilometer or more in size along Bennu's path in 2135. Thanks to the analyses made possible by the OSIRIS-REx spacecraft, scientists were able to rule out 24 of these keyholes, leaving only two remaining.
According to scientists, the most likely date for a collision would be in 2182. If this occurs, the event would be catastrophic. Lindley Johnson from NASA's Planetary Defense Coordination Office stated that "the size of the crater is usually between 10 to 20 times that of the object." Therefore, for Bennu, the crater diameter would range from 5 to 10 kilometers. However, "the area of destruction would be much larger, up to 100 times the size of the crater," according to Johnson. He also mentioned that researchers have knowledge of about 79% of asteroids the size of Bennu that are close to Earth.
