The asteroid Bennu is an ancient carbonaceous asteroid that has rocks and dusts from the birth of the solar system. It was thought that study of a sample from the asteroid Bennu collected directly in space would shed light on how planets were formed and how life began on Earth. OSIRIS-REx, NASA’s first asteroid sample return mission was launched in 2016 to near-Earth asteroid Bennu. It delivered the sample capsule to Earth on 24 September 2023. The in-depth study of the returned sample has now been completed, and the results were published on 29 January 2025. The returned sample has a large amount of ammonia and nitrogen-rich soluble organic matters that are key to life on Earth. The key organic compounds detected in the sample are amino acids (including 14 of the 20 found in the living systems on Earth), amines, formaldehyde, carboxylic acids, polycyclic aromatic hydrocarbons and N-heterocycles (including all five nucleobases found in DNA and RNA on Earth). Further, the sample also had salt minerals formed due to evaporation of brine that existed early in the parent body of the asteroid Bennu, suggesting salt water in the early history could have served as a medium for chemical interaction between the molecules detected in the sample. Detection of building blocks for life and salt minerals in the pristine sample collected in space directly from the asteroid Bennu and studied under contamination-control measures gives credence to the idea that the precursors for the emergence of life were widespread in the early solar system. Therefore, there is some possibility of life emerging on other planets or their natural satellites. Conditions at the asteroid Bennu is also a representative of Earth’s early history. It gives an idea about the ingredients present in the solar system before emergence of life on Earth.
Asteroid Bennu is a near-Earth orbit asteroid thought to have formed about 4.5 billion years ago in the early phase of history of solar system. It is a B-type, carbonaceous asteroid that has rocks and dust from the birth of the solar system. It was thought that Bennu may also have material containing molecules that were present when life formed on Earth. Asteroids rich in organics are thought to have played a role in catalysing life on Earth. The study of sample brought from the asteroid Bennu was expected to throw light on how planets were formed and how life began. NASA’s OSIRIS-REx mission aimed at this.
The asteroid sample return mission OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification and Security – Regolith Explorer) was launched to the near-Earth asteroid Bennu on 8 September 2016. It collected a sample of rocks and dust from the surface of the asteroid on 20 October 2020 and started its return journey to Earth on 10 May 2021. Travelling for two and a half years in its return journey, on 24 September 2023, it released the capsule containing rocks and dust sample collected from the asteroid Bennu into Earth’s atmosphere and continued its journey further to another near-Earth asteroid Apophis as OSIRIS-APEX mission.
The capsule containing sample of rocks and dust weighing about 250 grams collected from the asteroid Bennu landed safely on Earth at Utah site near Salt Lake City in the USA the same day on Sunday 24 September 2023. The returned sample has now been studied in-depth, and the results were published on 29 January 2025.
The analysis of the returned sample by one research team revealed presence of large amount of ammonia and nitrogen-rich soluble organic matters that are key to life on Earth. The organic compounds detected in the sample are amino acids (including 14 of the 20 found in the living systems on Earth), amines, formaldehyde, carboxylic acids, polycyclic aromatic hydrocarbons and N-heterocycles (including all five nucleobases found in DNA and RNA on Earth that are used to store and transmit genetic information to the offsprings). High abundance of ammonia in the sample is significant because ammonia can react with formaldehyde to form amino acids in right conditions. Interestingly, the amino acids with chirality in the sample from Bennu are racemic or equal mixture of both left- and right-hand versions. On Earth, living systems exclusively have left-handed version. Perhaps, amino acids on early earth were racemic mixture and the left-handed chirality of life on Earth evolved later due to some unknown reason.
Further, the other research team found salt minerals in the sample that included sodium-bearing phosphates and sodium-rich carbonates, sulphates, chlorides and fluorides. These salts formed due to evaporation of brine that existed early in the parent body of the asteroid Bennu. The salt water in the early history could have served as a suitable medium for chemical interaction between the molecules detected in the sample.
The organic matters and the mineral salts have been detected before in the meteorites, but exposure to Earth’s atmosphere complicates interpretation as they are easily destroyed or altered on entering Earth’s environment.
Detection of building blocks for life and evaporites (salt minerals formed after evaporation of brine) in the pristine sample collected in space directly from the asteroid Bennu and studied under contamination-control measures is novel. This gives credence to the idea that the precursors for the emergence of life were widespread in the early solar system. Therefore, there is some possibility of life emerging on other planets or their natural satellites. Conditions at the asteroid Bennu is also a representative of Earth’s early history. It gives an idea about the ingredients present in the solar system before emergence of life on Earth.
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References:
- Glavin, D.P., et al. 2025. Abundant ammonia and nitrogen-rich soluble organic matter in samples from asteroid (101955) Bennu. Nat Astron. Published: 29 January 2025. DOI: https://doi.org/10.1038/s41550-024-02472-9
- McCoy, T.J., et al. 2025. An evaporite sequence from ancient brine recorded in Bennu samples. Nature 637, 1072–1077. Published: 29 January 2025. DOI: https://doi.org/10.1038/s41586-024-08495-6
- NASA. News – NASA’s Asteroid Bennu Sample Reveals Mix of Life’s Ingredients. Posted 29 January 2025. Available at https://www.nasa.gov/news-release/nasas-asteroid-bennu-sample-reveals-mix-of-lifes-ingredients/
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Related article:
- NASA’s OSIRIS-REx Mission brings sample from asteroid Bennu to Earth (26 September 2023).
- near-Earth asteroid 2024 BJ to make closest approach to Earth (26 January 2024)
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