CAPE CANAVERAL, Fla. (AP) — An asteroid that NASA used for target practice several years ago was pushed into a slightly different orbit around the sun, scientists reported Friday, a discovery that could help deflect incoming killer space rocks in the future.
This is the first time someone has deliberately altered the orbit of a celestial body around the sun. The asteroid struck by NASA’s Dart spacecraft never posed a threat to Earth.
“This study marks a significant step forward in our ability to prevent future asteroids from impacting Earth,” the international team of researchers wrote in Science Advances.
According to scientists, the changes are small – just a tenth of a second and one-half mile (720 meters) less, compared with the two years and hundreds of millions of miles (kilometres) that take one orbit of the sun.
“Although this may seem small, a tiny deflection … can add up over decades and result in potentially hazardous asteroids hitting or missing Earth in the future,” lead author Raheel Makadia of the University of Illinois at Urbana-Champaign said in an email.
As with any planet-saving test, “the key is not to give a huge push at the last moment. The key is to give a small push many years in advance,” he added.
The Dart spacecraft, launched in 2021 in the world’s first planetary defense exercise, deliberately crashed into Dimorphos, which orbits a larger asteroid Didymos as they orbited the sun together. The space agency quickly determined that the 2022 impact had tweaked the smaller asteroid’s orbit around its larger companion.
But only now have scientists confirmed, based on observations from around the world, that the impact shortened the time the two planets orbit the sun by 0.15 seconds. Each solar orbit lasts 769 days, which amounts to a real-time deceleration of just over 10 micrometers per second, shrinking the asteroid’s 300 million mile (480 million km) orbit by 2,360 feet (720 meters).
Researchers say all the boulders and other debris thrown off Dimorphos during the crash gave Dimorphos as much thrust as the spacecraft itself, doubling the momentum. Last summer, a U.S. and Italian research team estimated that 35 million pounds (16 million kilograms) of rock and dust were ejected.
The good news is that even if the orbits of asteroids change, Earth will still be safely out of the way of them for the foreseeable future. That’s why this rubble-strewn system was chosen for the mission, said Steven Chesley of NASA’s Jet Propulsion Laboratory, who was involved in the study.
“While this is just one experiment, it is still an important data point that will be relevant to any future asteroid deflection mission,” Chesley said in an email.
When the European Space Agency’s Hera spacecraft reaches the asteroid in November, scientists hope to learn more about the impact’s aftermath. Dimorphos has a diameter of 525 feet (160 meters). According to new research, the rapidly spinning Didymos is 2,560 feet (780 meters) in diameter and 200 times more massive than its assistant.
Unlike Dart, Hera will not attack, but will follow Dart for months of measurements. A pair of small experimental probes will peel off and attempt a landing.
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