NASA’s Dramatic Double Asteroid Redirection Test (DART) has been a resounding success, scientists say.
Before the DART spacecraft deliberately crashed into Dimorphos on September 26, 2022, scientists knew very little about the asteroid’s size, shape, or composition. Six months later, they now have the clearest view of its entire body, which is 580 feet (177 meters) wide.
“It looks to me like a happy fish swimming to the left with its nose up,” Carolyn Ernst, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory (APL), said of the new high-resolution mosaic. Dimorphos, which was released on Monday (March 13) at the 54th Lunar and Planetary Science Conference (LPSC), taking place in Texas and virtually.
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The mosaic was assembled using the last 10 images sent home by the Didymos Reconnaissance and Asteroid Camera for Optical Navigation (DRACO), a camera aboard DART that took a picture of Dimorphos every second for the last four hours before the DART impact.
“I knew the final images would be impressive, and somehow they still managed to exceed my expectations,” said Nancy Chabot, APL planetary scientist. Chabot attributed the success of the mission to the collaboration of a huge team that included scientists from 100 institutions in 28 countries.
The DART impact reduced the time Dimorphos needed to orbit its larger asteroid companion Didymos by 33 minutes to 11 hours and 23 minutes. To get this number, scientists studied the Didyma binary system using telescopes located on all seven continents.
Over 259,000 images taken by DRACO are now available online as part of NASA’s Planetary Data System. (will open in a new tab). These images show some of the 2.2 million pounds (1 million kilograms) of ejecta ejected by Dimorphos from the impact and show that the asteroid’s surface is covered in boulders of varying sizes, helping researchers confirm that the asteroid is a pile of rubble.
Using this data, the scientists reconstructed the final moments of DART, including the collision itself. According to Ernst, the probe’s target was 25 inches (66 centimeters) wide. That’s smaller than the cross section of DART, so the star tracker that flew out of the bottom of the probe was likely the first to get hit. Microseconds later, the DART solar panels hit one of the Dimorphos boulders, but one part of the spacecraft didn’t have time to tell the others about the impact, Ernst said.
The scientists also announced on Monday that the names of five objects on the surface of Dimorphos have been accepted by the International Astronomical Union (IAU), the body that names celestial objects.
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(Image credit: NASA/Johns Hopkins APL)
Some of the new research presented included the latest highlights of DART and Hubble Space Telescope observations of ejecta and tail formations. The results, which were released on March 1, underlined that this is the first time the mission has observed Dimorphos growing not one, but two tails. (Astronomers have previously spotted asteroids with tails, but they’ve never seen any of the shapes.) The Hubble Space Telescope will keep observing until Didymos gets too close to the Sun to be safely observed, which will happen in early July.
The scientists also said that DART created a crater ranging from 130 feet (40 m) to 196 feet (60 m) wide when it sank between two boulders – Atabake and Bodran – on Dimorphos.
All this drama was being watched directly by LICIACube (short for “Light Italian Cubesat for Imaging of Asteroids”), a satellite weighing 31 pounds (14 kg) less than a shoebox, who boarded DART and departed. to a safe distance two weeks before impact. The satellite recorded everything it saw, including a bright flash immediately after DART’s collision with Dimorphos.
“From a scientific point of view, this is a treasure trove,” said Maurizio Paiola, a planetary scientist at the Italian National Institute of Astrophysics and a member of the LICIACube science team.
For the “outstanding contribution” of DART to the space sphere, the mission team was awarded (will open in a new tab) National Space Club and 2023 Nelson P. Jackson Aerospace Award earlier in March.
The knowledge gained so far from DART’s success is critical, scientists say, but this alone is not enough to understand the mission’s impact in the broader context of planetary defense. Applying a similar “kinetic impactor” technique to another asteroid hazard will require much more research, they say, and ongoing research into how the resulting ejecta will develop and behave will play an important role.
Using all the data sent home via DART and other data collected by ground-based telescopes, scientists hope to get a better idea of what to expect when the European Space Agency’s Hera spacecraft reaches the Didymos-Dimorphos system in 2026.
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