Samples of the asteroid Bennu returned to Earth by the OSIRIS-REx probe contain signs of aquatic history and indicate a possible origin from a protoplanetary world with an ocean.
Bennu Samples
Unusual Composition Discovery
September 24, 2023 In 2019, the space agency NASA received a capsule with carbon regolith collected from the near-Earth asteroid Bennu by the OSIRIS-REx probe after a seven-year journey. The resulting samples turned out to be the largest reservoir of unchanged asteroid material on our planet. Initial analysis found in the samples carbon, water and the unexpected presence of magnesium sodium phosphate, an ionic compound consisting of magnesium cations (Mg2+), sodium (Na+) and phosphate anion (PO43-).
Hypothesis about the water past
The presence of magnesium sodium phosphate, commonly found in some terrestrial minerals and geological formations, came as a surprise to the researchers as the substance was not seen in the OSIRIS-REx remote sensing data prior to sampling. Its presence on Bennu may indicate that the asteroid was once part of a vanished, primitive ocean world. According to OSIRIS-REx principal investigator Dante Lauretta of the University of Arizona, the state of phosphates and other elements on Bennu suggests a potentially wet past for the asteroid.
Composition of Bennu regolith
The regolith sample obtained by the probe on October 20, 2020 using the Touch-and-Go collection mechanism consists primarily of magnesium phyllosilicates - serpentines and smectites. These types of rocks are commonly found at the Earth's mid-ocean ridges. Comparing Bennu's serpentinites with their terrestrial counterparts could shed light on the asteroid's geological past. At the same time, surface materials still contain some of the original features of the protoplanetary disk from which the planets of the solar system formed. The study also confirmed that Bennu is rich in carbon, nitrogen and some organic compounds - important components for life on Earth.
Glossary
- OSIRIS-REx - NASA spacecraft to study and collect samples of the asteroid Bennu
- Bennu is a small near-Earth B-type asteroid, a relatively rare carbon asteroid
- Touch-and-Go (TAGSAM) - OSIRIS-REx probe sample collection mechanism using a special head on an articulated arm
- Philosilicates - class of silicate minerals containing silicon, oxygen and metal cations
- Serpentines - a group of phyllosilicate minerals formed by the hydration of ultramafic rocks
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Why is the OSIRIS-REx mission considered important for science?
What unexpected discoveries were made while studying samples from Bennu?
What does the composition of the samples tell us about the past of asteroid Bennu?
What components important for life were found in Bennu samples?
What do the results of the OSIRIS-REx mission mean for understanding the origin of the Solar System?
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Discussion of the topic – Asteroid Bennu: Secrets of a small planet-ocean revealed by scientists
Samples of regolith from the asteroid Bennu collected by NASA showed that it was once part of a small ocean planet. Scientists can now study unique material to learn more about the early history of the solar system.
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