A Powerful Recoil Effect Amplified NASA’s Asteroid Deflection Experiment

Composite image of the Didymos-Dimorphos system taken on November 30, showing its new ejecta tail.

Scientists continue to dig into the results of NASA’s incredibly successful DART test to deflect a harmless asteroid. As the latest findings suggest, the recoil created by Dimorphos’ spitting debris explosion after impact was significant, further enhancing the spacecraft’s influence on the asteroid.

NASA’s refrigerator-sized spacecraft crashed into the 535-foot-long (163-meter) Dimorphos on September 26, shortening its orbit around its larger partner, Didymos, by 33 minutes. This equates to several tens of feet, demonstrating the feasibility of using kinetic impactors as a means of deflecting threatening asteroids.

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A stunning side effect of the test was the gigantic, complex plumes that emanated from the asteroid after impact. The Didymos-Dimorphos system, located 7 million miles (11 million kilometers) from Earth, even sprouted a long tail as a result of the experiment. DART, short for Double Asteroid Redirection Test, had a profound impact on Dimorphos, kicking up a surprising amount of debris, or “ejecta,” in the parlance of planetary scientists.

Dimorphos, as we learned, is a rubble-pile asteroid, rather than a dense, tightly packed rocky body. This no doubt contributed to the excessive amount of ejected debris, but scientists weren’t quite sure how much debris the asteroid threw up following the impact. Preliminary results presented Thursday at the American Geophysical Union’s fall meeting in Chicago shed new light on this and other aspects of the DART mission.

Not only did DART launch tons of ejecta, but it also triggered a recoil effect which again served to push the asteroid in the desired direction, as Andy Rivkin, survey team leader explained. DART, during the meeting. “We got a lot for our money,” he told BBC News.

Indeed, if Dimorphos had been a more compact body, the same level of recoil would likely not have occurred. “If you detonate material at the target, you have a recoil force,” explained DART mission scientist Andy Cheng of Johns Hopkins University’s Applied Physics Laboratory, who also spoke during the presentation. meeting. The resulting recoil is analogous to releasing a ball; as the air comes out, it pushes the ball in the opposite direction. In the case of Dimorphos, the ejecta stream served as the air coming out of the balloon, which also pushed the asteroid in the opposite direction.

Planetary scientists are beginning to get an idea of ​​the amount of debris being moved. DART, traveling at 14,000 miles per hour (22,500 km/h), hit with enough force to knock more than 2 million pounds of material into the void. That’s enough to fill about six or seven railcars, NASA said in a statement. That estimate could actually be low, and the real figure could be 10 times higher, Rivkin said at the meeting.

Scientists assigned DART’s impulse factor, known as “beta”, a value of 3.6, meaning that the impulse transferred into Dimorphos was 3.6 times greater than an impact event. which produced no ejecta plume. “The result of that recoil force is that you put more momentum into the target and end up with a bigger deflection,” Cheng told reporters. “If you’re trying to save the Earth, it makes a big difference.”

This is a good point, as these values ​​will dictate the parameters of an actual mission to deflect a legitimately dangerous asteroid. Cheng and his colleagues will now use these results to infer beta values ​​for other asteroids, a task that will require a deeper understanding of an object’s density, composition, porosity and other parameters. Scientists also hope to determine how far the initial DART hit moved the asteroid and how much of its motion occurred due to recoil.

The speakers also produced another number – the length of the tail, or ejecta plume, that formed as a result of the impact. According to Rivkin, Dimorophos sprouted a tail measuring 18,600 miles (30,000 km) long.

“The asteroid impact was just the beginning,” Tom Statler, DART program scientist and presenter at the meeting, said in the statement. “Now we’re using the observations to study what these bodies are made of and how they formed, as well as how to defend our planet if an asteroid were ever heading our way.”

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