The NASA/ESA Hubble Space Telescope captured a series of images of rapid changes in the asteroid Dimorphos when it was deliberately struck by a 545-kilogram spacecraft on September 26, 2022. The primary goal of the NASA mission, dubbed DART (Double Asteroid Redirection Test), was to test our ability to alter the asteroid’s orbit as it orbits its larger companion asteroid, Didymos. While Dimorphos poses no threat to Earth, data from the mission could help researchers determine how to alter an asteroid’s path away from Earth, if necessary.
Hubble’s resulting time-lapse movie of the aftermath of the collision reveals surprising and remarkable changes as dust and chunks of debris from the injured asteroid were flung into space. Traveling at 13,000 miles per hour, the DART impactor collided head-on with the asteroid, ejecting more than 900,000 kilograms of dust from the asteroid.
The Hubble film offers valuable new clues about how the debris was scattered in a complex pattern in the days following the impact.
The film depicts three overlapping stages of the crash’s aftermath: the formation of an ejection cone, the spiral swirl of debris collected along the asteroid’s orbit around its companion asteroid, and the tail drawn by the pressure of sunlight behind the asteroid. is wiped.
The Hubble movie starts 1.3 hours before impact. In this view, both Didymos and Dimorphos are in the central point of light; not even Hubble can resolve the two asteroids separately. The thin, straight points protruding from the center (seen in later images) are artifacts of Hubble’s optics. The first post-impact snapshot is two hours after the event. Debris flies away from the asteroid and moves inward at a range of speeds in excess of four miles per hour (fast enough to escape the asteroid’s gravity so it doesn’t fall back onto the asteroid). The ejecta forms a largely hollow cone with long, stringy filaments.
About 17 hours after the collision, the debris pattern entered a second phase. The dynamic interaction within the binary system began to distort the cone shape of the ejection pattern. The most prominent structures are rotating, pinwheel-shaped features. The pinwheel is linked to the gravity of the companion asteroid Didymos.
Hubble then captures the debris dragged into a comet-like tail by the pressure of sunlight on the tiny dust particles. This extends into a debris train where the lightest particles are fastest and farthest from the asteroid. Hubble also recorded the tail splitting in two over a few days.
ESA’s Hera mission, due to launch in October 2024, will conduct a detailed post-impact survey of the targeted asteroid Dimorphos. Hera will turn the large-scale experiment into a well-understood and repeatable planetary defense technique that could one day actually be used.
Like Hubble and the NASA/ESA/CSA James Webb Space Telescope, NASA’s DART and ESA’s Hera missions are great examples of what international cooperation can achieve; the two missions are supported by the same teams of scientists and astronomers and work through an international collaboration called AIDA – the Asteroid Impact and Deflection Assessment.
NASA and ESA collaborated in the early 2000s to develop asteroid monitoring systems, but recognized that there was a missing link in the chain between asteroid threat identification and ways to address that threat. In response, NASA monitored the DART mission, while ESA developed the Hera mission to collect additional data on the impact of DART. With the Hera mission, ESA is taking on an even greater responsibility to protect our planet and ensure that Europe plays a leading role in the collective effort to address asteroid risks. As the flagship planetary defender of Europe, Hera is supported through the Agency’s Space Safety Program, part of the Operations Directorate.
- Li, JY., Hirabayashi, M., Farnham, TL et al. Ejecta from the DART-produced active asteroid Dimorphos. Nature (2023). DOI: 10.1038/s41586-023-05811-4