Asteroid Bennu, a mysterious and ancient space rock, has been shedding new light on the solar system’s early days. Samples of Bennu collected by NASA’s OSIRIS-REx mission in 2020 have provided valuable insights into its origins, revealing that it is a mixture of dust from our solar system, organic matter from interstellar space, and pre-solar system stardust.
According to scientists at NASA and other institutions, the asteroid Bennu is thought to be the remnant of a larger parent asteroid destroyed by a collision in the asteroid belt. A trio of newly published papers have analyzed the Bennu samples, providing evidence that its ancestor was made up of diverse materials from near and far beyond our solar system.
The analysis shows that some of these materials escaped chemical processes driven by heat and water, despite very low odds, and even survived an extremely energetic collision that formed Bennu. This suggests that the asteroid’s parent body accumulated material from various sources, including near the Sun and in interstellar space.
Researchers also found evidence of stardust grains with compositions that predate the solar system, organic matter likely formed in interstellar space, and high-temperature minerals formed closer to the Sun. These findings are significant because they provide a record of the solar system’s history and suggest that asteroids can hold secrets about its early days.
The transformation of Bennu’s materials was dramatic, with most being altered by reactions with water. The asteroid accumulated ice and dust, which melted to form liquids reacting with solids. This process is believed to have occurred over billions of years, leaving behind the sample we see today – 80% minerals containing water.
New research has also revealed microscopic craters and tiny splashes of once-molten rock on the surface of Bennu, indicating that it was bombarded by micrometeorites. These impacts, combined with solar wind effects, are known as space weathering, which is an important process affecting all asteroids.
The study highlights the importance of collecting samples from asteroids like Bennu to understand their role in the history of our solar system. The next step in unraveling this story will be the return of Moon rocks by the Artemis III astronauts, providing a new window into the solar system’s past.
Source: https://science.nasa.gov/missions/osiris-rex/nasas-bennu-samples-reveal-complex-origins-dramatic-transformation