Scientists continue to investigate the results of NASA’s failed shield to deflect a harmless asteroid. As the latest findings suggest, the terrifying blast of debris created by the Dimorphus vomitus after the impact was significant, further boosting the impact of space on the asteroid.
NASA’s spacecraft broke into the 535-foot-long (163-meter) Dimorphos on September 26, a shorter orbit around its larger companion Didymos, by a whopping 33 minutes. That equates to several dozen feet, demonstrating the feasibility of using impactors in motion as a means of deflecting threatening asteroids.
A side-effect of the test was the giant and tangled hairs that emanated from the asteroid after the impact. The Didymos-Dimorphos system, located 7 million miles (11 million kilometers) from Earth, also sported a long tail just in case. DART, short for Double Redirection Asteroid Test, had a deep impact on Dimorphos, kicking up a surprising amount of debris, or “ejectors” in the parlance of planetary scientists.
Dimorphos, as we have seen, is a pile of asteroid stones, the opposite of which is a dense and closely packed rocky body. This undoubtedly contributed to the excessive debris ejected, but scientists were not quite sure how much debris the asteroid shed as a result of the impact. Preliminary findings presented Thursday at the American Geophysical Union meeting in Chicago this fall shed new light on this and other aspects of the launch mission.
Not only did the DART kick off tons of ejecta, it also triggered the effects of the trigger that still served to knock the asteroid in the desired direction, as Andy Rivkin, DART research team lead, explained at the meeting. “We got a lot of bang for the buck,” he told BBC News.
Indeed, if Dimorphos had had a denser body, the same level of accidents would probably not have occurred. “If the materials blow off the target then they have energy,” explained DART mission scientist Andy Cheng of the Johns Hopkins University Applied Physics Lab, who also spoke at the meeting. The escape from it is analogous to a blown bladder; as the air goes out, it takes off in the opposite direction. In Dimorphos, a jet stream appeared instead of air coming out of the balloon, which also pushed the asteroid in the opposite direction.
Planetary science is beginning to make sense of how much debris has been moved. DART, traveling at 14,000 miles per hour (22,500 km/hour), struck with enough force over 2 million pounds of matter into the void. This is enough to fill six or seven rail cars, NASA said in a statement. That estimate could actually be on the lower side, and the true figure could be 10 times higher, Rivkin said at the meeting.
Scientists assigned the momentum factor to DART, known as “beta,” a value of 3.6, indicating that the momentum transferred to Dimorphos was 3.6 times greater than the impact event that produced no ejected plume. “The effect of that force is that you put more weight on the target, and you end up with a bigger limp,” Cheng told reporters. “If you’re trying to save the Earth, this makes a big difference.”
That’s a good thing, as those parameter values will dictate the actual mission to deflect a legitimately dangerous asteroid. Cheng and colleagues will now use these results to infer the beta values of other asteroids, a task that will require a deeper understanding of the material’s density, composition, porosity and other parameters. Scientists also hope to figure out the degree to which DART’s initial impact moved the asteroid and how much of its movement was due to recoil.
The speakers also adduce another figure of the length of the tail or of the ejected feather, which is formed in the blow of the blow. According to Rivkin, Dimorophus sprouted a tail measuring 18,600 miles (30,000 km long).
“The asteroid impact is just the beginning,” Tom Statler, DART program scientist and speaker at the meeting, said in a statement. “We are now using observations to investigate what these bodies are and how they were formed,” and how our planet shields asteroids heading our way.
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