The OSIRIS-REx Mission and Bennu

The OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security – Regolith Explorer) mission launched in September 2016 with the goal of collecting a sample from Bennu, a near-Earth asteroid. Bennu was chosen because it is a carbonaceous asteroid, meaning it contains a high proportion of carbon, and is considered a time capsule from the early solar system. The asteroid is roughly 500 meters (1,600 feet) in diameter.

The spacecraft spent over two years orbiting Bennu, mapping its surface and studying its composition before briefly touching down to collect a sample of regolith – loose rocks and dust – on October 20, 2020. The sample capsule parachuted into the Utah desert on September 24, 2023, marking the first U.S. asteroid sample return mission.

key Findings: A Disrupted Protoplanet

Initial analysis of the Bennu samples reveals a surprisingly high abundance of carbon-bearing minerals, including hydrated phyllosilicates.These minerals suggest that Bennu’s parent body was once rich in water and underwent hydrothermal activity – a process involving hot water circulating through rock – early in its history. This challenges the previous assumption that carbonaceous asteroids formed in the colder outer solar system.

Perhaps the most important finding is the evidence that Bennu isn’t a pristine remnant of the early solar system, but rather a fragment of a much larger asteroid, approximately 100 kilometers (62 miles) in diameter, that was catastrophically broken apart by a collision billions of years ago. This larger asteroid likely formed in the inner solar system, closer to the Sun.

The samples also contain organic molecules, the building blocks of life, though scientists have not yet determined if these molecules are of extraterrestrial origin or were introduced by contamination. Further analysis is needed to determine the complexity and origin of these organic compounds.

Implications for the Origin of Water and Life on Earth

The discovery that Bennu’s parent body originated in the inner solar system has significant implications for understanding the delivery of water and organic molecules to Earth.It supports the theory that these essential ingredients for life were not solely delivered by asteroids from the outer solar system, but also by asteroids originating closer to the Sun.

The presence of hydrated minerals in the samples suggests that water was abundant in the inner solar system early in its history. Collisions between asteroids like Bennu’s parent body and Earth could have delivered considerable amounts of water to our planet,contributing to the formation of oceans.

The organic molecules found