In 2022, NASA rammed a spacecraft into an asteroid to see if it could alter its orbital period around its parent asteroid. The mission, dubbed the Double Asteroid Redirection Test (DART), aimed to determine whether humanity could theoretically save itself from a catastrophic asteroid impact.<\/p>\n
DART collided with Dimorphos, a small moonlet orbiting a larger asteroid called Didymos, on September 26, 2022. The results of the impact blew NASA\u2019s expectations out of the water, shortening Dimorphos\u2019s orbital period by 32 minutes. Such a change would be more than enough to deflect a dangerous asteroid away from Earth, indicating that this strategy\u2014the kinetic impactor technique\u2014could save us if necessary. New research, however, complicates this success story. An investigation into the debris DART left behind suggests this technique, when applied to planetary defense, isn\u2019t as\u00a0straightforward as scientists initially thought.<\/p>\n
\u201cWe succeeded in deflecting an asteroid, moving it from its orbit,\u201d said study lead author Tony Farnham, a research astronomer at the University of Maryland, in a statement<\/a>. \u201cOur research shows that while the direct impact of the DART spacecraft caused this change, the boulders ejected gave an additional kick that was almost as big. That additional factor changes the physics we need to consider when planning these types of missions.\u201d Farnham and his colleagues published their findings in The Planetary Science Journal<\/a> on July 4.<\/p>\n Dimorphos is a \u201crubble pile\u201d asteroid, a loose conglomeration of material such as rocks, pebbles, and boulders held together by gravity. This study only applies to this type of asteroid. Had DART collided with a more coherent, solid body, the impact wouldn\u2019t have produced these bizarre effects. Still, there are plenty of other rubble pile asteroids in the galaxy, so understanding how they respond to the kinetic impactor technique is important.<\/p>\n The researchers analyzed images taken by LICIACube, an Italian Space Agency satellite that was mounted on the DART spacecraft. About two weeks before the impact, LICIACube separated<\/a> and began following about three minutes behind the spacecraft, allowing the satellite to beam images of the collision and its effects back to Earth. In addition to observing the crater DART punched into the surface of Dimorphos, LICIACube captured the ejecta plume, or the cloud of debris ejected from the asteroid when DART hit it.<\/p>\n These images allowed Farnham and his colleagues to track 104 boulders ranging from 1.3 to 23.6 feet (0.4 to 7.2 meters) wide. The rocks shot away from the asteroid at speeds up to 116 miles per hour (187 kilometers per hour). Strangely, the distribution of this ejected debris was not random, defying the researchers\u2019 expectations.<\/p>\n \u201cWe saw that the boulders weren\u2019t scattered randomly in space,\u201d Farnham said. \u201cInstead, they were clustered in two pretty distinct groups, with an absence of material elsewhere, which means that something unknown is at work here.\u201d<\/p>\n The larger of the two clusters, which contained 70% of the debris, shot southward away from the asteroid at high speeds and shallow angles. The researchers believe these objects came from a specific source on Dimorphos\u2014perhaps two large boulders called Atabaque and Bodhran that shattered when DART\u2019s solar panels slammed into them moments before the main body of the spacecraft hit.<\/p>\n