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‘Watershed moment for planetary defense’: DART impact changes asteroid’s orbit

WASHINGTON — It’s not quite the drama of the movie “Armageddon,” but a NASA spacecraft intentionally changed the orbit of a celestial object.

Analysis of data obtained over the past two weeks by NASA’s Double Asteroid Redirection Test (DART) investigation team shows the spacecraft’s kinetic impact altered the orbit of the asteroid Dimorphos.

This marks humanity’s first time purposely changing the motion of a celestial object and the first full-scale demonstration of asteroid deflection technology.

“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 proven we are serious as a defender of the planet.

“This is a watershed moment for planetary defense and all of humanity, demonstrating commitment from NASA’s exceptional team and partners from around the world.”

Prior to DART’s impact, it took Dimorphos 11 hours and 55 minutes to orbit its larger parent asteroid, Didymos, NASA said. Since DART’s intentional collision with Dimorphos on Sept. 26, astronomers have been using telescopes on Earth to measure how much that time has changed.

The investigation team has confirmed the spacecraft’s impact altered Dimorphos’ orbit around Didymos by 32 minutes, shortening the 11 hour and 55-minute orbit to 11 hours and 23 minutes. This measurement has a margin of uncertainty of approximately plus- or minus-2 minutes, the space agency said.

Before its encounter, NASA had defined a minimum successful orbit period change of Dimorphos as 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” said Lori Glaze, director of NASA’s Planetary Science Division at NASA Headquarters in Washington. “As new data come in each day, astronomers will be able to better assess 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.”

The space agency said the investigation team is still acquiring data from observatories around the world and 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.

Focus now is shifting toward measuring the efficiency of momentum transfer from DART’s roughly 14,000 mph 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, NASA said.

To understand the effect of the recoil from the ejecta, more information on of the asteroid’s physical properties, such as the characteristics of its surface, and how strong or weak it is, is needed. These issues are still being investigated.

“DART has given us some fascinating data about both asteroid properties and the effectiveness of a kinetic impactor as a planetary defense technology,” said Nancy Chabot, the DART coordination lead from the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland. “The DART team is continuing to work on this rich dataset to fully understand this first planetary defense test of asteroid deflection.”

Neither Dimorphos nor Didymos poses any hazard to Earth before or after DART’s controlled collision with Dimorphos, NASA said.

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