On September 24, 2023, a landmark event occurred in the field of space exploration when NASA successfully returned asteroid samples collected by the OSIRIS-REx probe to Earth. After a seven-year journey through the Solar System, this historic mission recovered approximately 120 grams of pristine carbonaceous regolith from the near-Earth asteroid Bennu.
Collecting samples from the asteroid Bennu
The mission OSIRIS-REx was launched with the aim of collecting samples from Bennu, a small B-type asteroid known for its carbon-rich composition and its proximity to Earth. After several years of observations and preparation, the space probe used its Touch-and-Go Sample Acquisition Mechanism (TAGSAM) to sample regolith from a particularly promising site, the Hokioi crater of Bennu, also known as the site name Nightingale.
The recovered samples were then carefully packaged in a special capsule and returned to Earth on September 24, 2023. They now represent the largest reservoir of unaltered asteroid material ever recovered, providing scientists with a unique opportunity to study materials that have not been modified by the Earth’s atmosphere or other processes.
Scientific discoveries and implications
Initial analyzes of the samples revealed expected components such as carbon and water, confirming hypotheses about Bennu’s composition based on prior observations. However, an unexpected discovery captivated the attention of researchers: the presence of magnesium sodium phosphatean ionic compound often associated with vital biochemical processes on Earth.
The presence of this phosphate on Bennu suggests potentially aqueous origins for the asteroid, raising questions about its history and evolution. Magnesium-containing phyllosilicates, identified as the main constituents of the regolith samples, also offer clues about the geological conditions in which Bennu formed and evolved over time.
This discovery suggests that Bennu’s parent body was an object filled with water, which opens new perspectives on the geological and chemical processes that shaped this distant asteroid. This body could have been a primitive celestial object, probably made of materials from the cloud of gas and dust from which our Solar System formed.
These discoveries open up new perspectives for space research, providing crucial data on the formation processes of the Solar System and the prebiotic chemistry that could have contributed to the conditions favorable to the emergence of life on Earth. They also highlight the importance of sample return missions for our understanding of asteroids and for our preparation for possible cosmic threats.
