To the researchers' surprise, phosphate was found in a sample of material brought back from the asteroid Bennu by NASA's OSIRIS-REx spacecraft.
During initial analyses, the Bennu dust sample found carbon, nitrogen and organic compounds essential for life as we know it. Clay minerals, particularly serpentinite, are the most common in the samples, and their composition is typical of mid-ocean ridges, where material flows from beneath the crust and meets ocean water. Magnesium sodium phosphate (MgNaO) found in the sample4P) It allows us to conclude that Bennu could have broken off from an ancient ocean-covered celestial body. The presence of phosphate came as a surprise to researchers because the probe’s field tests had not detected it. Although similar phosphate was found in the sample returned by the Japanese Hayabusa-2 probe from the asteroid Ryugu in 2020, the phosphate from Bennu is particularly pure and contains larger grains than any meteorite previously studied.
NASA launched OSIRIS-REx in 2016. (Origins, Spectral Interpretation, Resource Identification, Security – Soil Explorer) The probe brought back a sample weighing 121.6 grams from the asteroid Bennu, and the capsule containing the precious material arrived on Earth in September 2023. The results of the first analyses were presented by researchers in June of this year. Meteorites and Planetary Science In the magazine It was published.The main conclusion they reached was that as a result of the tests, they got what they had hoped for: thanks to the ancient material, a glimpse into the past of a watery world rich in carbon and nitrogen.
The capsule containing the samples from Bennu arrives on September 24, 2023 at the Utah Test and Training Range (UTTR), where it is first transferred to the UTTR portable clean room.image(NASA/Keegan Barber)
The analysis provides insight into the asteroid’s chemical composition. The interaction of volcanic rocks with water produces not only clay minerals, but also many other minerals such as carbonates, iron oxides, and iron sulfides. However, experts examining the samples consider the presence of water-soluble sulfides to be an unexpected discovery, as these compounds play an important role in life on Earth. The presence of magnesium and sodium phosphates on Bennu also raises many questions about the geochemical processes that may have occurred on the celestial body in the past. According to the lead author of the aforementioned publication, the presence and condition of the phosphates point to Bennu’s watery past. From this, they conclude that Bennu could have been part of a larger watery celestial body, but this hypothesis still needs to be proven through further investigation.
Different types of rocks on Bennu's surface. In the bottom two images, veins containing light material that reflects light well can be clearly seen. All images were taken with the OSIRIS-REx PolyCam.image(NASA/Goddard/University of Arizona)
Despite the possible past interaction with water, Bennu is chemically a primitive and ancient celestial body, and the physical composition of its heavy elements is similar to that of the Sun. This composition provides insight into the very early past of the solar system, 4.5 billion years ago, because the rocks were preserved in their original state, and did not melt or solidify again during the celestial body's history.
The open science package in the NASA Johnson Space Center (JSC) glove box, with the cylindrical TAGSAM sampling head in the middle.image:NASA)
Researchers who examined the samples from Bennu confirmed that the celestial body’s material is rich in carbon and nitrogen. Their presence could lead to understanding the processes that once formed the chemical basis for life on Earth. As they noted, it’s especially important to bring back samples of material from asteroids, because when chunks of cosmic rock naturally reach Earth, it’s these light, all-important materials that burn up first as they pass through the atmosphere.
The Bennu material is almost dark in color. It has a long grain about 1 mm long, from which the smaller piece shown on the right has broken off.image:Laurita et al. 2024)
A micrograph of a small portion of a sample of material taken from the asteroid Bennu. In the upper left image, the Bennu material is almost dark in color. Its grains are about 1 mm long, covered by a thin phosphate shell. The other three SEM images show grain details at increasing magnification.image:Laurita et al. 2024)
Bennu's material samples are being held at NASA's Johnson Space Center, but in the near future, the samples will be delivered to dozens of laboratories in the United States and other countries for various tests.
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Related Links:
Surprise finding of phosphate in sample taken from asteroid Bennu (NASA)
NASA Osiris-Rex
