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The double asteroid redirection test successfully changed the trajectory of the asteroid Dimorphos when the NASA spacecraft intentionally crashed into space rock on September 26, according to the agency.
The DART mission, a large-scale demonstration of diversion technology, was the world’s first conducted in the name of planetary defense. The mission was also the first time humanity had intentionally changed the motion of a celestial object in space.
Before impact, Dimorphos took 11 hours and 55 minutes to orbit its larger parent asteroid, Didymos. Astronomers used ground-based telescopes to measure how Dimorphos’s orbit changed after the impact.
Now it takes Dimorphos 11 hours and 23 minutes to go around Didymos. The DART spacecraft changed the moonlet asteroid orbit for 32 minutes.
Initially, astronomers expected that DART would be successful if it shortened the trajectory by 10 minutes.
“All of us have a responsibility to protect our home planet. After all, it’s the only one we have,” said NASA Administrator Bill Nelson.
“This mission shows that NASA is trying to be ready for whatever the universe throws at us. NASA has shown that we are serious as defenders of the planet. This is a watershed moment for planetary defense and for all of humanity, demonstrating the commitment of the exceptional team at NASA and its partners around the world.”
Neither Dimorphos nor Didymos pose a threat to Earth, but the double-asteroid system was a perfect target for testing deflection technology, according to the DART team.
“For the first time in history, humanity has changed the orbit of a planetary object,” said Lori Glaze, director of NASA’s Planetary Science Division.
“As new data comes in every day, astronomers will be able to better assess if, and how, a mission like DART could be used in the future to help protect Earth from a collision with an asteroid if we ever discover one in our path. ”
The DART team continues to collect data by observing the double asteroid system, and the orbital measurement may become more accurate in the future. Currently, there is an uncertainty of plus or minus two minutes.
A new image of Dimorphos, captured by the Hubble Space Telescope, shows that the debris trail’s comet tail has split in two. Scientists are still working to understand the meaning of the split.
The team is now focusing on measuring how much momentum was transferred from DART to Dimorphos. At the moment of impact, the spacecraft was moving at about 14,000 miles per hour (22,530 kilometers per hour). Astronomers will analyze the amount of rocks and dust thrown into space after the impact.
The DART team believes that the recoil of the plume “substantially enhanced” the spacecraft’s thrust against the asteroid, not unlike the release of air from a balloon propelling it in the opposite direction, according to NASA.
“Although we’ve done more to the system than just change the orbit, we may have left Dimorphos reeling a bit,” said Tom Statler, NASA’s DART program scientist. “So over time there may be some interaction between the wobble and the orbit and things will adjust. But it will certainly never go back to the old 11 hour 55 minute orbit.”
Astronomers are still investigating Dimorphos’s surface and how faint or strong it is. The DART team’s first look at Dimorphos, provided by DART before the accident, suggests that the asteroid is a mass of debris held together by gravity.
Images continue to return from the Light Italian CubeSat for Imaging of Asteroids, or LICIACube, the mini satellite provided by the Italian Space Agency that accompanied as a robotic photojournalist on the DART mission.
In about four years, the European Space Agency’s Hera mission will also fly over the double asteroid system to study the crater left by the collision and measure the mass of Dimorphos.
“DART has given us some fascinating data on the properties of asteroids and the effectiveness of a kinetic impactor as a planetary defense technology,” said Nancy Chabot, DART coordination lead at Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. “The DART team continues to work on this rich dataset to fully understand this first asteroid deflection planetary defense test.”
The research team chose Dimorphos for this mission because its size is comparable to that of asteroids that could pose a threat to Earth. A Dimorphos-sized asteroid could cause “regional devastation” if it hits Earth.
Near-Earth objects are asteroids and comets with an orbit that puts them within 48.3 million kilometers (30 million miles) of Earth. Detecting the threat of near-Earth objects that could cause serious damage is a primary focus of NASA and other space organizations around the world.
No asteroids are currently on a direct impact course with Earth, but there are more than 27,000 near-Earth asteroids in all shapes and sizes.
Finding populations of dangerous asteroids and determining their sizes are top priorities for NASA and its international partners. The design of a space-based telescope called Near Earth Object Surveyor Mission is currently under review.
“We shouldn’t be too eager to say that a test on one asteroid tells us exactly how any other asteroid would behave in a similar situation,” Statler said. “But what we can do is use this test as an anchor point for our physical calculations in our simulations that tell us how different types of impacts should behave in different situations.”
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