The Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) was a NASA mission aimed at studying and retrieving samples from the near-Earth asteroid 101955 Bennu 🔗. Launched on September 8, 2016, the spacecraft embarked on a seven-year journey to enhance our understanding of the early Solar System and the origins of organic compounds that may have contributed to life on Earth.
OSIRIS-REx’s primary objective was to collect and return at least 60 grams of material from Bennu’s surface. The mission sought to analyze Bennu’s physical and chemical properties, providing insights into planetary formation and the potential for resource utilization in future space exploration.
Journey and Operations
After its launch, OSIRIS-REx performed an Earth gravity assist on September 22, 2017, to adjust its trajectory toward Bennu. The spacecraft arrived at the asteroid on December 3, 2018, initiating a detailed survey to map Bennu’s surface and identify suitable sampling sites. On October 20, 2020, OSIRIS-REx executed a touch-and-go (TAG) maneuver, successfully collecting surface material using its Touch-And-Go Sample Acquisition Mechanism (TAGSAM).
Following the successful collection, OSIRIS-REx departed Bennu on May 10, 2021, beginning its return journey to Earth. The sample return capsule re-entered Earth’s atmosphere and landed in the Utah desert on September 24, 2023. The retrieved samples are expected to provide valuable information about the early Solar System and the building blocks of life.
With its primary mission complete, OSIRIS-REx has been renamed OSIRIS-APEX (Apophis Explorer). The spacecraft is now tasked with studying the near-Earth asteroid 99942 Apophis, with an expected arrival in April 2029. This extended mission aims to further our understanding of asteroid composition and behavior.
Key Discoveries
The OSIRIS-REx mission has provided groundbreaking discoveries about asteroid Bennu, shedding light on the early Solar System and the processes that shape planetary bodies. Here are the key findings:
- Water-Bearing Minerals: Analysis of Bennu’s surface revealed the presence of hydrated minerals, indicating that liquid water once existed on Bennu’s parent body. This suggests that carbon-rich asteroids like Bennu may have played a role in delivering water and organic molecules to early Earth.
- Organic Compounds: Preliminary studies identified carbon-rich compounds on Bennu’s surface. These materials are critical for understanding the origins of life, as they may contain the building blocks of organic chemistry.
- Surface Activity: OSIRIS-REx observed ejecta events, where small particles were periodically released from Bennu’s surface into space. This unexpected activity indicates that Bennu is a dynamically active body, providing new insights into asteroid evolution.
- Surface and Subsurface Composition: Bennu’s surface is rougher and rockier than initially expected, with large boulders scattered across it. This finding challenged existing theories about asteroid surfaces and impacted the design of the sample-collection maneuver. The sample acquisition process revealed a soft, loosely packed surface, described as behaving more like a “ball pit” than a solid layer, which affects our understanding of asteroid geology.
- Bennu’s Shape and Rotation: Bennu has a distinct spinning-top shape, caused by its rapid rotation. OSIRIS-REx detected that Bennu’s rotation rate is gradually increasing, likely due to the YORP effect (a phenomenon where sunlight alters an asteroid’s spin).
- Sample Collection: During the touch-and-go (TAG) maneuver, OSIRIS-REx collected surface material, with scientists confirming the sample exceeded the mission’s goal of 60 grams, making it the largest extraterrestrial sample returned to Earth since the Apollo missions.
- Hazard Assessment: Bennu is classified as a potentially hazardous asteroid, and OSIRIS-REx refined its orbital predictions. It is now understood that Bennu has a very low chance of impacting Earth in the late 22nd century.
Legacy
OSIRIS-REx represents a significant achievement in space exploration, marking the United States’ first mission to return samples from an asteroid. The data and materials obtained are anticipated to shed light on the Solar System’s formation and the origins of organic matter, contributing to our broader understanding of planetary science.
