Joint Press Release
Shogo Tachibana (Professor, Department of Earth and Planetary Science, Japan Aerospace Exploration Agency)

Japan Agency for Marine-Earth Science and Technology (JAMSTEC; President: Hiroyuki Yamato) The international collaborative research group led by Dr. Toshihiro Yoshimura, Deputy Senior Researcher, and Dr. Yoshinori Takano, Senior Researcher, at the Biogeochemistry Research Center, and Prof. Hiroshi Naraoka, Graduate School of Science, Kyushu University, is a joint research group with the Graduate School of Science, The University of Tokyo, National Institute of Advanced Industrial Science and Technology (AIST), Horiba Advanced Techno Co. The group, together with researchers from the Graduate School of Science at the University of Tokyo, National Institute of Advanced Industrial Science and Technology, Horiba Techno, Horiba Techno Service, Thermo Fisher Scientific Japan Group, Hokkaido University, and Tokyo Institute of Technology, conducted precise chemical analysis of soluble components in samples from the asteroid Ryugu to determine their composition, content, etc. The results of the analysis are shown in Table 1. The composition and content of the soluble components were clarified.

Asteroid Ryugu is one of the primordial bodies that retain the chemical composition of the entire solar system before the birth of the Earth. The initial analysis of Hayabusa2 has revealed various properties, contents, and history of the asteroid, but the material information of ionic components among soluble components has remained unknown.

In this study, soluble components were extracted from samples of the asteroid Ryugu and precisely analyzed at the inorganic and organic molecular levels. The results showed that hydrothermal extracts, which reflect the most soluble components, are very rich in sodium ions (Na+). Sodium ions act as electrolytes that stabilize the surface charge of minerals and organic matter, and some are thought to precipitate as sodium salts (Salt) by binding with organic molecules and other substances. Various organosulfur molecules were also found in the extract. It is thought that the chemical state of the organic sulfur molecules in the water on the asteroid Ryugu changed, resulting in the chemical evolution of a wide variety of organosulfur molecules.

This finding is important not only for unraveling the material evolution of the early solar system, but also for answering the major question of how they led to the chemical processes that ultimately led to the birth of life.

The results were published in the scientific journal Nature Communications on September 18, 2023 (JST).

For more information, please refer to the following

Graduate School of Science web: https://www.s.u-tokyo.ac.jp/ja/press/10021/
Publication URL: https://www.nature.com/articles/s41467-023-40871-0

On Monday, August 7, 2023, students from Nada Junior High School and Nada Senior High School visited UTOPS. We gave them a mock lecture about the Hayabusa2 exploration and the rock brought back from the asteroid Ryugu.

On Friday, August 4, 2023, students from Komatsu High School in Ishikawa, Japan, visited UTOPS. We gave a mock lecture on the Hayabusa2 exploration and the rock brought back from the asteroid Ryugu.

On August 1 (Tue.) and 2 (Wed.), 2023, we held an astronomy lab for students from Matsumoto Fukashi High School in Nagano Prefecture and Kariya High School in Aichi Prefecture. The students estimated the distance to galaxies from photographs of galaxies and used the recession velocity of those galaxies to determine the age of the Universe.

Joint Press Release
Shogo Tachibana (Professor, Department of Earth and Planetary Science)
Takeshi Iizuka (Associate Professor, Department of Earth and Planetary Science)

A research team led by Associate Professor Wataru Fujiya of the Graduate School of Science and Engineering, Ibaraki University, Associate Professor Noriyuki Kawazaki and Professor Hisayoshi Yurimoto of the Graduate School of Science, Hokkaido University, Professor Tetsuya Yokoyama of the Department of Earth and Planetary Science, Graduate School of Science, Tokyo Institute of Technology, and Professor Shogo Tachibana of the Graduate School of Science, University of Tokyo, has analyzed samples from the asteroid Ryugu samples recovered by the Hayabusa2 spacecraft, and have elucidated the evolution of oxygen concentrations and gas molecular species present on Ryugu.

In this study, we examined the abundance ratios of carbon and oxygen isotopes in the carbonate minerals (calcite and dolomite) in Ryugu’s samples. The results showed that the isotope ratios of both carbon and oxygen in calcite varied greatly among the different particles, while those in mafic calcite varied little. These results suggest that calcite formed early in the alteration process at Ryugu, when temperatures and oxygen concentrations were rising and the fraction of gas species was changing, while the calcite was formed at higher temperatures and with a relatively high fraction of carbon dioxide in the gas, while the system was in equilibrium.

Such isotopic compositions of carbonate minerals have not been reported in previous meteorite studies. This suggests that Ryugu and its meteorite parent bodies were composed of different materials and evolved in unique environments.

The results were published online in Nature Geoscience on Wednesday, July 10, 2023.

For more information, please see

Graduate School of Science web: https://www.s.u-tokyo.ac.jp/ja/info/8544/
Publication URL: https://www.nature.com/articles/s41561-023-01226-y

Joint Press Release
Motohide Tamura, Professor, Department of Astronomy)

More than 5,000 exoplanets have been discovered so far, but most of them were discovered through indirect observations, and only about 20 of them were directly imaged by direct imaging, which captures light from exoplanets directly. This is because direct imaging has so far been used to search for exoplanets blindly by observing a large number of objects, because it is not possible to narrow down the target of observation.

However, the advent of satellites that can precisely measure the positions of fixed stars on the celestial sphere has overcome this situation. Using precise astrometry data from the Gaia satellite launched by the European Space Agency and its predecessor, the Hipparcos satellite, it became possible to obtain indirect evidence for the existence of a planet from the wobble (accelerated motion) of a star and directly image promising objects using large telescopes and super-compensation optics. This is the first time that a direct imaging method has become possible using large telescopes and super-compensation optics.

An international research team led by researchers from the University of Tokyo’s Graduate School of Science has now successfully discovered a new exoplanet, HIP 99770 b, by direct imaging using this technique and the Subaru Telescope’s supercompensating optics instrument (see Figures 1 and 2). This exoplanet orbits the star HIP 99770, which is 130 light years away in the constellation Cygnus and is visible to the naked eye with an apparent brightness of 4th magnitude, 17 times the distance between the Sun and Earth. By taking into account the stellar wobble data, the mass of the exoplanet was estimated to be 15 ± 1 times the mass of Jupiter, which is a much more precise estimate for an exoplanet found by direct imaging.

Planets discovered with this technique are ideal for demonstrating the high-contrast observations that will be made with the ground-based Very Large Telescope in the future. It is also a promising technique for imaging Earth’s twin in the future.

The results of this research were published as Currie et al. “Direct Imaging and Astrometric Detection of a Gas Giant Planet Orbiting an Accelerating Star” in the US The results of this research were published in the U.S. scientific journal Science on April 13, 2023.

Professor Motohide Tamura of the Department of Astronomy participated in this research.

For more information, please visit the website of NAOJ Hawaii Observatory and NAOJ. The results are also available at the Center for Astrobiology.

Following enormous collisions, such as asteroid impacts, some amount of material from an impacted world may be ejected into space. This material can travel vast distances and for extremely long periods of time. In theory this material could contain direct or indirect signs of life from the host world, such as fossils of microorganisms. And this material could be detectable by humans in the near future, or even now.

When you hear the words vacuum and dust in a sentence, you may groan at the thought of having to do the housework. But in astronomy, these words have different connotations. Vacuum of course refers to the void of space. Dust, however, means diffuse solid material floating through space. It can be an annoyance to some astronomers as it may hinder their views of some distant object. Or dust could be a useful tool to help other astronomers learn about something distant without having to leave the safety of our own planet. Professor Tomonori Totani from the University of Tokyo’s Department of Astronomy has an idea for space dust that might sound like science fiction but actually warrants serious consideration.

“I propose we study well-preserved grains ejected from other worlds for potential signs of life,” said Totani. “The search for life outside our solar system typically means a search for signs of communication, which would indicate intelligent life but precludes any pre-technological life. Or the search is for atmospheric signatures that might hint at life, but without direct confirmation there could always be an explanation that does not require life. However, if there are signs of life in dust grains, not only could we be certain, but we could also find out soon.”

The basic idea is that large asteroid strikes can eject ground material into space. There is a chance that recently deceased or even fossilized microorganisms could be contained in some rocky material in this ejecta. This material will vary in size greatly, with different-sized pieces behaving differently once in space. Some larger pieces might fall back down or enter permanent orbits around a local planet or star. And some much smaller pieces might be too small to contain any verifiable signs of life. But grains in the region of 1 micrometer (one-thousandth of a millimeter) could not only host a specimen of a single-celled organism, but they could also potentially escape their host solar system altogether, and under the right circumstances, maybe even venture to ours.

“My paper explores this idea using available data on the different aspects of this scenario,” said Totani. “The distances and times involved can be vast, and both reduce the chance any ejecta containing life signs from another world could even reach us. Add to that the number of phenomena in space that can destroy small objects due to heat or radiation, and the chances get even lower. Despite that, I calculate around 100,000 such grains could be landing on Earth every year. Given there are many unknowns involved, this estimate could be too high or too low, but the means to explore it already exist so it seems like a worthwhile pursuit.”

There may be such grains already on Earth, and in plentiful amounts, preserved in places such as the Antarctic ice, or under the seafloor. Space dust in these places could be retrieved relatively easily, but discerning extrasolar material from material originating in our own solar system is still a complex matter. If the search is extended to space itself, however, there are already missions that capture dust in the vacuum using ultralight materials called aerogels.

Papers

Tomonori Totani, “Solid grains ejected from terrestrial exoplanets as a probe of the abundance of life in the Milky Way,” International Journal of Astrobiology: March 22, 2023, doi:10.48550/arXiv.2210.07084.
Link (Publication)

Related links

• Graduate School of Science
• Department of Astronomy
• Institute of Astronomy