New Findings from NASA’s DART Mission: Analyzing Debris and Revealing the Structure of Asteroid Dimorphos
In a groundbreaking mission, NASA’s Double Asteroid Redirect Test (DART) successfully collided with the asteroid Dimorphos in 2022, marking a significant milestone in planetary defense technology. The impact resulted in a noticeable shift in Dimorphos’ orbit around its larger neighbor, Didymos. Since then, scientists have been diligently analyzing the data collected from various observatories to unravel the mysteries of Dimorphos’ composition and shed light on the impact’s profound effect on its orbit.
One crucial aspect of this analysis comes from the small CubeSat called LICIACube, which accompanied DART on its mission. LICIACube, equipped with narrow and widefield imagers named LEIA and LUKE, trailed DART through the impact area, capturing images before and after the collision. These images revealed a complex field of debris, challenging the notion of a simple cone of material. Instead, researchers discovered filaments and clumps of ejecta moving at different speeds.
One notable finding from the analysis is the identification of a stream of ejected material that extended over eight kilometers from the impact site, moving at a velocity of about 50 meters per second. Additionally, two clumps of material were observed, with one traveling at approximately 75 meters per second and the other at half that rate. The fastest-moving material tracked reached an astonishing speed of 500 meters per second, emphasizing the value of LICIACube’s observations compared to previous ones conducted by the Hubble telescope.
Interestingly, the ejected material initially appeared reddish in tint but gradually shifted to a more blue hue over time. Scientists speculate that this color change may indicate that the asteroid’s surface had been reddened by radiation exposure. The first material to exit the impact likely originated from the surface, while subsequent material originated from the asteroid’s interior, resulting in the observed color shift.
Another significant finding relates to the dimensions of the debris cone. By working backward from these dimensions, researchers estimated that the material originated from a crater approximately 65 meters in diameter. This information is crucial for understanding the impact’s effectiveness and its influence on Dimorphos’ orbit. While DART’s momentum alone cannot account for the entirety of the orbital change, the exchange of momentum caused by debris from the impact played a significant role.
Furthermore, scientists utilized the LICIACube data on ejected material to estimate the internal properties of Dimorphos. By employing a collision physics model and testing various internal compositions based on density, solid rock content, and other characteristics, they found that a relatively low-density porous body with minimal large boulders near the surface provided the best results. This suggests that DART likely caused global disruption to Dimorphos’ structure.
The weak and fragmented structure observed in Dimorphos is reminiscent of other “rubble pile asteroids” like Bennu and Ryugu. This fragility aligns with models proposing that Dimorphos formed when Didymos shed material, some of which remained gravitationally bound and ended up in orbit. The formation process may have involved solar heating, which increased Didymos’ spin until it could no longer retain all its material. As a result, lighter material was shed from the surface, potentially explaining the relatively small size of the material in Dimorphos.
Excitingly, more detailed data on the post-impact system will be available in the coming years. The European Space Agency (ESA) plans to launch the Hera probe in late 2024, which will enter orbit around the Didymos/Dimorphos system. This mission aims to provide comprehensive insights into the aftermath of the collision, further advancing our understanding of these celestial bodies.
In conclusion, NASA’s DART mission and the subsequent analysis of the data collected by LICIACube have unveiled fascinating revelations about the structure and composition of asteroid Dimorphos. These findings not only deepen our knowledge of asteroids but also contribute to the development of planetary defense technologies. With the upcoming Hera mission, scientists anticipate even more groundbreaking discoveries that will shape our understanding of these enigmatic celestial objects.