NASA has announced that its experimental spacecraft Double Asteroid Redirection Test (DART) successfully altered the orbit of asteroid Dimorphous. After two weeks of data collection and analysis, the agency found that DART’s impact shortened the asteroid’s rotation around its parent, Didymos, by 32 minutes.
“All of us have a responsibility to protect our home planet. After all, it’s the only one we have,” NASA Administrator Bill Nelson, the administrator of NASA, said. “This mission shows that NASA is trying to be ready for whatever the universe throws at us. NASA has proven we are serious as a defender of the planet. This is a watershed moment for planetary defence and all of humanity, demonstrating commitment from NASA’s exceptional team and partners from around the world,” he added.
Before DART’s impact, it took Dimorphos 11 hours and 55 minutes to orbit its more giant parent asteroid, Didymos. Since DART’s intentional collision with Dimorphos on September 26, astronomers have been using telescopes on Earth to measure how much that time has changed.
Dimorphous
Now, the investigation team has confirmed the spacecraft’s impact altered Dimorphos` orbit around Didymos by 32 minutes, shortening the 11-hour and 55-minute rotation to 11 hours and 23 minutes. This measurement has a margin of uncertainty of approximately plus or minus 2 minutes. Before its encounter, NASA had defined a minimum successful orbit period change of Dimorphos as a change of 73 seconds or more. This early data show DART surpassed this minimum benchmark by more than 25 times. “This result is one important step toward understanding the full effect of DART’s impact with its target asteroid,” Lori Glaze, director of NASA’s Planetary Science Division at NASA Headquarters in Washington, said. “As new data come in each day, astronomers will be able to assess better whether 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 headed our way,” Lori added. The investigation team is still acquiring data from ground-based observatories around the world and with radar facilities at NASA Jet Propulsion Laboratory’s Goldstone planetary radar in California and the National Science Foundation’s Green Bank Observatory in West Virginia.
“DART has given us some fascinating data about both asteroid properties and the effectiveness of a kinetic impactor as a planetary defence technology,”
They are updating the period measurement with frequent observations to improve its precision. The focus is shifting toward measuring momentum transfer efficiency from DART’s roughly 22,530-kilometer per-hour collision with its target. This includes further analysis of the “ejecta” – the many tons of asteroidal rock displaced and launched into space by the impact. The recoil from this blast of debris substantially enhanced DART’s push against Dimorphos – a little like a jet of air streaming out of a balloon sends the balloon in the opposite direction. More information on the asteroid’s physical properties, such as the characteristics of its surface and how strong or weak it is needed to understand the effect of the recoil from the ejecta. These issues are still being investigated. “DART has given us some fascinating data about asteroid properties and the effectiveness of a kinetic impactor as a planetary defence technology,” Nancy Chabot, the DART coordination lead from the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, said.
“The DART team continues working on this rich dataset to understand this first planetary defence test of asteroid deflection fully.” For this analysis, astronomers will continue to study imagery of Dimorphos from DART’s terminal approach and from the Light Italian CubeSat for Imaging of Asteroids (LICIACube), provided by the Italian Space Agency, to approximate the asteroid’s mass and shape.
Roughly four years from now, the European Space Agency’s Hera project is also planned to conduct detailed surveys of both Dimorphos and Didymos, with a particular focus on the crater left by DART’s collision and a precise measurement of Dimorphos` mass. Johns Hopkins APL built and operated the DART spacecraft and managed the DART mission for NASA’s Planetary Defense Coordination Office as a project of the agency’s Planetary Missions Program Office.
