NASA’s Lucy spacecraft has made a remarkable discovery during its recent flyby of asteroid Dinkinesh in November 2023.
The mission revealed significant geological features and a fascinating new formation: a double moon named Selam. This rare configuration, known as a contact binary, formed from debris orbiting Dinkinesh after a significant geological event.
The Lucy mission aims to provide deeper insights into the formation and evolution of small bodies in the solar system, which are critical for understanding the history of planetary formation, including Earth.
Geological Features and Internal Dynamics
The November 2023 flyby provided detailed images showing a trough and a ridge on Dinkinesh, indicating its internal strength and complex history.
The spacecraft’s Long Range Reconnaissance Imager (L’LORRI) captured stereographic image pairs of these features, revealing that a large piece of the asteroid had shifted, forming these structures. This dynamic response to stress over millions of years has allowed scientists to better understand the asteroid's composition and behavior.
Scientists believe that as Dinkinesh rotated, small thermal forces generated a torque that gradually increased its rotation speed, building up centrifugal stresses until part of the asteroid shifted into a more elongated shape. This event likely caused debris to enter into a close orbit around Dinkinesh, which eventually formed the ridge and the contact binary moon, Selam. This process suggests that Dinkinesh has more internal strength than previously thought, behaving more like a solid rock rather than a loose pile of rubble.
Selam: the Double Moon
Selam, named after the Amharic word for “peace,” was initially discovered as a single small moon. However, further images revealed that it is actually composed of two smaller bodies fused together. This double-lobed structure points to a complex formation history involving material ejected from Dinkinesh during its geological evolution. The presence of this contact binary satellite provides valuable data about the mechanical properties and history of both Dinkinesh and Selam.
Lead investigator Hal Levison from the Southwest Research Institute explained that understanding the strengths and behaviors of small bodies like Dinkinesh is crucial for understanding planetary formation. “To understand the history of planets like Earth, we need to understand how objects behave when they hit each other, which is affected by the strength of the planetary materials,” Levison said. “We think the planets formed as zillions of objects orbiting the sun, like asteroids, ran into each other. Whether objects break apart when they hit or stick together has a lot to do with their strength and internal structure.”
Implications for Future Missions
The Lucy mission’s findings from Dinkinesh are just the beginning of its 12-year journey, which includes visits to nine more asteroids. The spacecraft is currently heading back towards Earth for a gravity assist maneuver in December 2024, which will propel it towards its next target, asteroid Donaldjohanson, in 2025. The mission’s primary focus is the Trojan asteroids near Jupiter, where Lucy will begin its exploration in 2027. These asteroids are considered “fossils” from the era of planet formation and hold key insights into the early solar system.
The discovery of Dinkinesh’s double moon and the detailed observations of its geological features provide a wealth of data for scientists. This information helps in reconstructing the history and evolution of these small bodies, shedding light on the dynamic processes that shaped them. As Lucy continues its journey, it promises to uncover more secrets about the solar system’s past, contributing to our understanding of how planets and their satellites form and evolve.
The Path Ahead for NASA's Lucy
As Lucy gears up for its next flyby in 2025, scientists and engineers are preparing to gather more detailed data from asteroid Donaldjohanson. This asteroid, named after the discoverer of the famous fossil Lucy, will provide another opportunity to study the composition and history of main-belt asteroids. Following this encounter, Lucy will head towards the Trojan asteroids, where it will explore eight of these ancient bodies over several years.
The Trojan asteroids are particularly intriguing because they have remained relatively unchanged since the early days of the solar system. By studying these primordial objects, scientists hope to gain a better understanding of the conditions and processes that prevailed during the formation of the planets. The data collected from these encounters will help refine models of solar system formation and evolution, offering new perspectives on how Earth and its neighbors came to be.
Collaboration and Innovation
The success of the Lucy mission is a testament to the power of collaboration and innovation in space exploration. The mission involves partnerships between NASA, the Southwest Research Institute, Lockheed Martin Space, and numerous other institutions and researchers. This collaborative effort has enabled the development of advanced technologies and instruments that are critical for the mission’s objectives.
For instance, the Long Range Reconnaissance Imager (L’LORRI) aboard Lucy has proven to be an invaluable tool for capturing high-resolution images of Dinkinesh and its moon Selam. These images provide detailed views of the asteroid’s surface features and its binary moon, allowing scientists to conduct in-depth analyses. The success of this instrument and others on the spacecraft highlights the importance of technological innovation in advancing our understanding of the solar system.