AsianScientist (Jan. 3, 2019) – Using the infrared camera of the AKARI satellite, a Japanese research team has detected the existence of water in the form of hydrated minerals in a number of asteroids. They reported their findings in the Publications of the Astronomical Society of Japan.
The Earth is the only planet in our solar system where the presence of water on the planet surface has been confirmed. However, the question of how Earth acquired water remains debatable.
Some scientists think that asteroids were responsible for carrying water to Earth—not in the form of liquid water, but rather as hydrated minerals, produced by chemical reactions between water and anhydrous rocks inside the asteroids. Thus, by searching for hydrated minerals, researchers can confirm whether asteroids were a source of water.
In the present study, Japanese researchers at Kobe University, the Japan Aerospace Exploration Agency and the University of Tokyo used the infrared camera of the AKARI satellite, launched in February 2006, to obtain spectra at near-infrared wavelengths from two to five micrometers, the spectral range within which hydrated materials can be detected and identified.
The researchers carried out spectroscopic observations of 66 asteroids and found evidence of hydrated minerals in C-type (carbonaceous) asteroids. These findings suggest that C-type asteroids were formed by the agglomeration of rocks and water ice which eventually gave rise to hydrated minerals.
The team also inferred that the hydrated minerals within these asteroids are being heated and therefore gradually losing water. The heating energy could be supplied by solar wind plasma, micrometeorite impacts or decay of radioactive isotopes in the rocks, said the researchers.
On the other hand, hydrated minerals were not detected in S-type (stony) asteroids. In the rare cases where faint signals of hydrated minerals were picked up by the AKARI satellite, the researchers determined that those signals were produced by hydrated materials that had been transferred onto the S-type asteroid during collisions with other hydrated asteroids.
“By solving this puzzle, we can make a significant step towards identifying the source of Earth’s water and unveiling the secret of how life began on Earth,” said Assistant Professor Fumihiko Usui of Kobe University, a co-author of the study, who added that this discovery will contribute to our understanding of the distribution of water in our solar system, the evolution of asteroids and the origin of water on Earth.
The article can be found at: Usui et al (2018) AKARI/IRC Near-infrared Asteroid Spectroscopic Survey: AcuA-spec.
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Source: Kobe University; Photo: Pixabay.
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