A powerful recoil effect magnified NASA’s asteroid deflection experiment
Scientists continue to closely study the results of NASA’s DART test, which was surprisingly successful, to deflect a harmless asteroid. As the latest findings suggest, the recoil created by the explosion of debris thrown up by Dimorphos after impact was significant, further increasing the spacecraft’s influence on the asteroid.
NASA’s fridge-sized spacecraft placed on the 535-foot-long (163-meter) Dimorphos on September 26, shortening its orbit around its larger companion, Didymos, for a whopping 33 minutes. That equates to several dozen feet, demonstrating the feasibility of use kinetic impactors as a means to deflect threatening asteroids.
A surprising side effect of the trial was the giant and complex tufts emanating from the asteroid after impact. The Didymos-Dimorphos system, located 7 million miles (11 million kilometers) from Earth, even sprouted a long tail in the wake of the experiment. DART, short for Double Asteroid Redirection Test, had a profound impact on Dimorphos, kicking up a surprising amount of debris, or “ejection,” in the jargon of planetary scientists.
Dimorphos, as we learned, is a rubble-pile asteroid, rather than a dense, tight rocky body. This undoubtedly contributed to the excessive amount of debris ejected, but scientists weren’t entirely sure how much debris the asteroid spewed as a result of the impact. Preliminary recommendations Presented Thursday at the American Geophysical Union’s fall meeting in Chicago shed new light on this and other aspects of the DART mission.
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DART not only launched tons of ejecta, but also triggered a recoil effect that served to push the asteroid in the desired direction, Andy Rivkin, leader of the DART research team, explained at the meeting. “We got a lot for the money,” he said. saying BBC News.
In fact, if Dimorphos had been a more compact body, the same level of recoil probably wouldn’t have occurred. “If you take material off the target, you have a recoil force,” explained DART mission scientist Andy Cheng of the Johns Hopkins University Applied Physics Laboratory, who also spoke at the meeting. The resulting recoil is analogous to releasing a balloon; as the air comes out, it pushes the balloon 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 how much debris was displaced. DART, traveling at 14,000 miles per hour (22,500 km/h), struck with enough force to spill more than 2 million pounds of material into a vacuum. That’s enough to fill about six or seven railcars, NASA said in a declaration. That estimate may actually be low, and the actual number could be 10 times higher, Rivkin said at the meeting.
The scientists assigned DART’s momentum factor, known as “beta,” a value of 3.6, meaning the momentum transferred to Dimorphos was 3.6 times greater than an impact event that did not produce an ejecta plume. . “The result of that recoil force is that you put more momentum on the target and end up with a bigger deflection,” Cheng told reporters. “If you’re trying to save the Earth, this makes a world of difference.”
That’s a good point, as those values will dictate the parameters for a real mission to deflect a legitimately dangerous asteroid. Cheng and his colleagues will now use these results to infer the beta values of other asteroids, a task that will require a deeper understanding of an object’s density, composition, porosity, and other parameters. The scientists also hope to determine the degree to which the initial DART impact moved the asteroid and how much of its movement occurred due to recoil.
The speakers also produced another figure: the length of the tail, or ejecta plume, that formed from the impact. According to Rivkin, Dimorophos sprouted a tail that was 30,000 km (18,600 mi) long.
“Impacting the asteroid was just the beginning,” Tom Statler, DART program scientist and meeting presenter, said in the statement. “Now we use the observations to study what these bodies are made of and how they formed, as well as how to defend our planet in case an asteroid is headed our way.”