NASA’s Hubble Space Telescope recently imaged debris from asteroid Dimorphos that was blasted away as a result of the agency’s Double Asteroid Redirection Test (DART) experiment that deliberately struck the asteroid on September 26, 2022, at 14,000 miles per hour. The impact, which was monitored by the LUKE (LICIACube Unit Key Explorer) camera onboard the Italian autonomous spacecraft, LICIACube, proved to be successful as NASA announced a few weeks later that the impact changed the asteroid’s orbit. While the goal of the experiment was to change the orbital period of Dimorphos by 73 seconds or greater, the data showed the impact changed the orbit by 32 minutes with a margin of error of approximately 2 minutes.
NASA Hubble image taken in December 2022 of asteroid Dimorphos with its debris field encircling the asteroid that was produced from the DART impact in September 2022. (Credit: NASA, ESA, David Jewitt (UCLA); Alyssa Pagan (STScI))
October 2022 video of Hubble observing the immediate aftermath of the DART impact.
Now almost one year later, Hubble has observed approximately 37 fragments of boulders and rubble drifting away from Dimorphos. They are estimated to be traveling at slightly over one-half mile per hour and range in size from three to 22 feet in diameter, and the combined mass of the debris is approximately 0.1 percent of the total mass of Dimorphos.
"This is a spectacular observation – much better than I expected,” said Dr. David Jewitt, who is a Distinguished Professor in the Department of Earth, Planetary & Space Sciences at UCLA and has been using Hubble to monitor changes in Dimorphos both pre- and post-impact from DART. “The numbers, sizes, and shapes of the boulders are consistent with them having been knocked off the surface of Dimorphos by the impact. The boulders are some of the faintest things ever imaged inside our solar system."
While Dr. Jewitt estimates that approximately two percent of the surface boulders were excavated from the impact, the mechanisms behind the excavation are still up for debate. Current hypotheses range from seismic activity caused by the impact to a possible ejecta plume. One reason behind all the debris could also be from the loose makeup of Dimorphos, which is hypothesized to be a weakly bound rubble pile that formed from the ejecta of a much larger asteroid, Didymos, and further observations are required to gain a better understanding of the processes at work.
Time-lapse video of the DART impact on asteroid Dimorphos, which is in orbit around Didymos.
"If we follow the boulders in future Hubble observations, then we may have enough data to pin down the boulders' precise trajectories. And then we’ll see in which directions they were launched from the surface," said Dr. Jewitt.
What new discoveries will astronomers make about the debris from Dimorphos, and what can it teach us about impacting asteroids in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
Sources: EurekAlert!, Wikipedia, Agenzia Spaziale Italiana, NASA, NASA (1), The Johns Hopkins University Applied Physics Laboratory
