Ryan Whitwam
2024-03-21 07:00:00
www.extremetech.com
In 2022, a NASA spacecraft smacked into an asteroid called Dimorphos, but unlike so many space collisions in recent years, this one was on purpose. The DART (Double Asteroid Redirection Test) went perfectly, with the impact proving that it is possible to nudge an asteroid’s orbit to prevent a future impact with Earth. NASA has been studying Dimorphos since the test, and researchers from the Jet Propulsion Laboratory (JPL) have confirmed that the DART collision significantly altered the asteroid’s shape.
NASA chose Dimorphos (above) as the target because it does not coast through space alone. This 560-foot (170-meter) space rock orbits a larger asteroid called Didymos. By monitoring how its orbit around the larger object changed, NASA could quickly and accurately assess DART’s impact. A new study published in the Planetary Science Journal analyzes those changes and the effect the collision had on the shape of Dimorphos.
“Dimorphos’ orbit is no longer circular,” said Shantanu Naidu, a JPL engineer and lead author of the study. “Its orbital period is now 33 minutes and 15 seconds shorter. And the entire shape of the asteroid has changed, from a relatively symmetrical object to a ‘triaxial ellipsoid’ – something more like an oblong watermelon.”
The researchers used three data sources to determine what happened to the space rock. The first was DART itself, which captured high-resolution images of Dimorphos as it approached. This allowed the team to precisely measure the space between Dimorphos and Didymos and determine all the physical parameters of the pre-impact Dimorphos. The second was NASA’s Goldstone Solar System Radar, which pinged the asteroids from its home in California to measure the position and velocity of both objects. The most significant contributor to the study was light curve data collected by ground-based telescopes worldwide. This refers to how sunlight reflecting off the asteroids changed over time and how the impact altered their motion in space.
Dimorphos changed shape after being struck by the impactor.
Credit: NASA / JPL-Caltech
According to the new study, the orbital changes didn’t happen all at once. The orbital period of Dimorphos dropped by 32 minutes and 42 seconds immediately after the impact. In the following weeks, it dropped another 32 seconds as the asteroid lost more rocky material to space. Dimorphos also orbits about 120 feet (37 meters) closer to Didymos than before the test.
The results support the idea that Dimorphos is a “rubble pile” object composed of loosely packed material. This may be similar to the asteroid Bennu, which nearly swallowed OSIRIS-REx whole when it collected a sample in 2020. Scientists hope to learn more about the structural changes to Dimorphos when the ESA’s upcoming Hera mission arrives. Hera is currently slated to launch in October 2024.