Thanks to some amazing Hubble Space Telescope observations, scientists are still amazed by NASA’s DART mission — this time in the form of a swarm of rocks that appear to have been freed from the target asteroid upon impact.
In September of last year, NASA launched a mission that on its surface might seem to contradict everything we know about space exploration. The agency launched a spacecraft directly at an asteroid. did not survive. But this metallic adventurer, called DART, which stands for Double Asteroid Redirect Test, had a very important purpose: It was NASA’s first step in developing an ambitious planetary defense system.
In short, the point of DART was to find out if a plane landing on a relatively small asteroid called Dimorphos that will change its orbit around a larger asteroid, Didymus. Not only was the mission a resounding success, but it also seems to be the gift that keeps on giving. We have been since I learned a little about the effects of space rocks and how, exactly, Earth’s future defense mechanism might someday work.
And on Thursday (July 20), NASA announced that DART has provided us with some interesting information once again from beyond the grave. Taking advantage of the powerful optics of the Hubble Space Telescope, astronomers found that the probe’s impact on Dimorphos — which occurred while it was flying at 14,000 mph (22,530 km/h) — produced a “swarm of rocks.” And the agency says that it is possible that these pieces are from the target of the asteroid itself.
Related: The epic DART asteroid crash: What NASA learned 5 months later
“This tells us for the first time what happens when you hit an asteroid and see material come out at larger sizes,” David Jewett, a planetary scientist at UCLA who has focused on studies of the DART effect, said. he said in a statement. “The rocks are some of the weakest objects ever imaged within our solar system.”
However, to be clear, a press release about these findings notes that the rocks weren’t likely shattered away from Dimorphos as a result of the DART collision, but rather were already on the asteroid’s surface and only dispersed upon impact. In reality, The final image of DART From the asteroid before its demise, two seconds after the impact, such small rocks and debris are visible as already present in Dimorphos.
According to a NASA statement, the rock’s ejection could be due to either what is known as an ejecta plume generated by the impact, or the seismic wave that shook it. (The latter would be similar to what would happen if you hit a loose rocky surface with a hammer, causing small rocks to vibrate freely across the surface.)
In terms of the rocks themselves, Jewett and his colleagues identified 37 free-flowing Dimorphos rocks ranging in size from three feet to 22 feet (0.9 meters to 6.7 meters) wide and having a combined mass of about 0.1% of the asteroid’s. These objects appeared to drift away from their source at just over half a mile per hour (0.8 km/h), which NASA likens to “almost at the walking speed of a giant tortoise.”
“This is a great observation — much better than I expected,” Jewett said. “We see a cloud of rocks carrying mass and energy away from the impact target. The numbers, sizes, and shapes of the rocks correspond to the fall off the surface of Dimorphos by the impact.”
Jewett added, “If we follow the rocks in future Hubble observations, we may have enough data to determine the exact trajectories of the rocks. And then we’ll see in which directions they were launched from the surface.”
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