On Tuesday, January 23, 2024, Professor Shogo Tachibana of UTOPS gave a talk on Ryugu and Hayabusa2 to fifth graders at Nakamura Elementary School in Nerima Ward, Tokyo.
From the first to the fourth period, we went around to each class and interacted with energetic children.
Please refer to the following URLs 「宇宙のお話１」「宇宙のお話２」 for the scenes of the day.
Joint Press Release
Shogo Tachibana (Professor, Department of Earth and Planetary Science, ISAS)
Since the surface of an asteroid is not covered by an atmosphere, solar winds and cosmic dusts fall on the asteroid and change the chemical composition and other characteristics of materials on the asteroid’s top surface. A research team led by Assistant Professor Megumi Matsumoto and Professor Tomoki Nakamura of the Department of Earth Sciences, Graduate School of Science, Tohoku University, in collaboration with Ritsumeikan University, Kyoto University, the University of Tokyo, and others, observed the surface of rock particles brought back from the asteroid Ryugu by the Hayabusa2 probe using a scanning electron microscope, and found that the surface of the asteroid is covered with molten materials of 5 to 20 micrometers in size, formed when small cosmic dust particles hit the asteroid. The team discovered several melts of 5 to 20 micrometers in size, which were formed by the impact of small cosmic dust particles on the asteroid’s surface. 3D CT observation and chemical composition analysis of the melts revealed that they were formed by the melting and mixing of dust from the impacting comet and Ryugu’s surface material at high temperatures.
Comets form in the distant part of the solar system and are known to contain a large amount of organic matter that could be the material for life. The formation of molten material from cometary dust impacts likely occurred in the orbit of the present-day asteroid Ryugu about 5 million years ago, suggesting that Ryugu was supplied with cometary dust containing organic matter from distant parts of the solar system until very recently.
The results of this study were published on January 19, 2024 in Science Advances, a journal published by the American Association for the Advancement of Science (AAAS).
For more information, please refer to the following
Graduate School of Science web: https://www.s.u-tokyo.ac.jp/ja/press/10185/
Publication URL: https://www.science.org/doi/10.1126/sciadv.adi7203
On January 20 (Sat.) and 21 (Sun.), 2024, we held an astronomy training for students from Suwa Seiryo High School, Suwa Futaba High School, Matsumoto Misuzugaoka High School in Nagano Prefecture, and Ena High School in Gifu Prefecture. The students estimated the distance to galaxies from photographs of galaxies and used the recession speeds of these galaxies to determine the age of the universe.
Joint Press Release
Shogo Tachibana (Professor, Department of Earth and Planetary Science, ISAS)
Reflection spectra of asteroid recovered samples and meteorites provide clues to identify the constituent materials of asteroids from observationally obtained reflection spectra of asteroids.
A research group led by graduate student Kana Amano (currently a visiting researcher) and Professor Tomoki Nakamura of the Department of Earth Sciences, Graduate School of Science, Tohoku University, researcher Moe Matsuoka of the National Institute of Advanced Industrial Science and Technology (AIST), and Professor Shogo Tachibana of the Department of Earth and Planetary Science, Institute of Space and Planetary Science, Graduate School of Science, the University of Tokyo, and their colleagues have been studying asteroid samples recovered by the asteroid probe Hayabusa2 from asteroid Ryugu sample recovered from the asteroid Ryugu by the asteroid explorer Hayabusa2, and measured the reflection spectrum of the sample by devising a way to prevent it from reacting with the Earth’s atmosphere. By comparing Ryugu samples, meteorites from the same type of asteroid as Ryugu, and experimentally heated meteorites, they showed that the reaction of the meteorites with water and oxygen in the Earth’s atmosphere changed their reflection spectra to be brighter than they were in space. Based on this achievement, it is expected that the accuracy of identifying the constituent materials of asteroids by observation will be improved by considering how the reflection spectra of meteorites can change due to their alteration on the ground.
This result was published in Science Advances, a journal published by the American Association for the Advancement of Science (AAAS), on December 7, 2023.
For more information, please refer to the following
Graduate School of Science web: https://www.s.u-tokyo.ac.jp/ja/press/10144/
Publication URL: https://www.science.org/doi/10.1126/sciadv.adi3789
Joint Press Release
Aki Takigawa (Associate Professor, Department of Earth and Planetary Science)
Shogo Tachibana (Professor, Department of Earth and Planetary Science, ISAS)
Icy bodies and comets born far from the sun contain large amounts of nitrogen compounds such as ammonium salts. Such nitrogen-containing solids are thought to be very important as material for life, but no evidence of their transport to the Earth’s orbital region has been found. In this study, we examined sand from Ryugu, an asteroid orbiting near Earth, using an electron microscope and discovered that the very surface of the sand is covered with nitrided iron (iron nitride: Fe4N). Iron nitride is found on the surface of a mineral composed of iron and oxygen atoms called magnetite. We hypothesized that the iron nitride was formed by a chemical reaction on the surface of the magnetite when a small meteorite containing a large amount of ammonia compounds from an icy body hit Ryugu. On the surface of the asteroid, oxygen is lost from the magnetite surface due to exposure to ionic winds (solar wind) from the sun, and metallic iron, which easily reacts with ammonia, forms on the very surface. This is assumed to have promoted the synthesis of iron nitride derived from ammonia on the surface of the magnetite. This micrometeorite may have come from an icy body in the distant solar system, and it is possible that a larger amount of nitrogen compounds than previously realized were transported to the solar system near Earth to provide the material for life.
This work was conducted by a group led by Dr. Toru Matsumoto, a specific assistant professor at the Hakubi Center, Kyoto University; Dr. Takaaki Noguchi, a professor at the Graduate School of Science; Dr. Ryo Miyake, an associate professor; Dr. Yohei Igami, an assistant professor; Dr. Mitsutaka Haruta, an associate professor at the Institute for Chemical Research; and international collaborators, and published online in the British international journal Nature Astronomy on November 30, 2023, in the It was published online in the British international journal Nature Astronomy on November 30, 2023.
Professor Shogo Tachibana and Associate Professor Aki Takigawa of the Department of Earth and Planetary Sciences participated in the research results.
For more information, please refer to the following
Graduate School of Science web: https://www.s.u-tokyo.ac.jp/ja/press/10130/
Publication URL: https://www.nature.com/articles/s41550-023-02137-z
Joint Press Release
Takeshi Iizuka (Associate Professor, Department of Earth and Planetary Science)
Shogo Tachibana (Professor, Department of Earth and Planetary Science, ISAS)
A research group led by Professor Tetsuya Yokoyama of the Department of Earth and Planetary Science, Faculty of Science, Tokyo Institute of Technology, Associate Professor Tsuyoshi Iizuka and Professor Shogo Tachibana of the Graduate School of Science, University of Tokyo, and Professor Hisayoshi Yurimoto of the Graduate School of Science, Hokkaido University has measured the isotopic composition of the Cb-type asteroid Ryugu, and found that intense water metamorphism and water circulation on Ryugu caused local heterogeneity in chromium isotopic composition, They found that local inhomogeneities in chromium isotopic compositions were caused by the intense water metamorphism and water circulation that occurred on Ryugu.
Initial analysis of Ryugu samples revealed that the chemical and mineral compositions of the Cb-type asteroid Ryugu are similar to those of Ivuna-type carbonaceous meteorites, but there is a slight discrepancy between Ryugu and Ivuna-type carbonaceous meteorites in terms of chromium nucleosynthesis origin isotopic anomalies, the cause of which has been awaited to be clarified. The research group has been waiting for the cause of the anomaly to be clarified.
The research group measured nucleosynthetic origin isotope anomalies of chromium (54Cr) and titanium (50Ti) in a total of five Ryugu samples. The results showed that the 54Cr isotopic anomaly varied significantly from higher to lower than the average value for Ivna-type meteorites. This variation is inversely correlated with that of chromium isotopes (53Cr) derived from radiolytic decay of manganese-53 (53Mn), a short-lived nuclide. The 54Cr isotopic anomaly in the combined Ryugu samples (7-24 mg) (about 90 mg) is consistent with the average value for Ivna-type carbonaceous meteorites. In the initial analysis of the Bennu samples brought back by OSIRIS-REx, it was found that it is desirable to analyze a certain amount of sample (>0.1 g) in order to avoid the influence of heterogeneity.
The results of this research were published online in Science Advances on November 9, 2023 Japan time.
For more information, please refer to the following
Graduate School of Science web: https://www.s.u-tokyo.ac.jp/ja/press/10087/
Publication URL: https://www.science.org/doi/10.1126/sciadv.adi7048
Joint Press Release
Kotaro Kono, Professor, Astronomy Education and Research Center)
An international research team led by Assistant Professor Takuma Izumi of the National Astronomical Observatory of Japan (NAOJ) has observed the Compass Galaxy in the nearby universe with the ALMA telescope at an extremely high resolution of about one light year, and succeeded in quantitatively measuring the gas flow and its structure on a spatial scale of only a few light years around a supermassive black hole in all phases: plasma, atomic and molecular. The result was the world’s first successful quantitative measurement of the gas flow and its structure in all phases of plasma, atoms, and molecules. As a result, the accretion flow toward the supermassive black hole was clearly observed, and it was also clarified that the accretion flow is caused by a physical mechanism called “gravitational instability”. Furthermore, it was found that the majority of the accretion flow is not used for the growth of the black hole, but is instead ejected as atomic or molecular gas from the vicinity of the black hole, and then returns to the gas disk to become accretion flow to the black hole again, as if a fountain-like gas cycle is taking place. This is an important achievement toward a comprehensive understanding of the growth mechanism of supermassive black holes.
These observation results were published in the American journal Science on November 3, 2023 as “Supermassive black hole feeding and feedback observed on sub-parsec scales” by Izumi et al. (DOI: 10.1126/science.adf0569).
Professor Kotaro Kono of the Center for Astronomy Education and Research is participating in this research.
For more information, please visit the website of NAOJ and NAOJ ALMA Project.
https://www.nao.ac.jp/news/science/2023/20231103-alma.html
Joint Press Release
Satoshi Kasahara (Associate Professor, Department of Earth and Planetary Science)
Professor Lynn Kistler, Professor Yoshizumi Miyoshi, and Project Associate Professor Tomoaki Hori of Nagoya University and their colleagues, Associate Professor Kazushi Asamura and Professor Iku Shinohara of the Japan Aerospace Exploration Agency, Associate Professor Satoshi Kasahara and Assistant Professor Kunihiro Keika of the University of Tokyo, and Associate Professor Shoichiro Yokota of Osaka University, and their colleagues in the United States discovered that the main cause of space storms is plasma originating from the Earth, rather than plasma originating from the Sun as previously thought.
Through international collaboration, the research team analyzed data from a total of four scientific satellites, including the Japanese Geospace Exploration Satellite Arase, NASA of the United States, and ESA of Europe. As a result, they succeeded for the first time in separating the composition of solar- and terrestrial-origin plasma in near-Earth space (geospace), and discovered that the plasma in the Earth’s magnetosphere changes from solar to terrestrial origin during space storms. They also identified that the Earth-origin hydrogen ions are initially dominant in the development of space storms, and that the Earth-origin oxygen ions later become the main cause of space storms.
This indicates that not only ions of solar origin, as previously thought, but also those of terrestrial origin influence the development of space storms. During space storms, the space environment around the Earth changes drastically, which can cause disturbances to satellites and strong electric currents on the ground, which can affect the power grid. This research indicates that an accurate understanding of the behavior of not only plasma from the sun but also from the earth is necessary to understand the changes in the space environment caused by space storms and to predict space storms, which will force a major change in the conventional understanding of space storms.
The research results were published in the British scientific journal Nature Communications on October 30, 2023, at 7:00 p.m. CST.
For more details, please refer to the following
Graduate School of Science web: https://www.s.u-tokyo.ac.jp/ja/press/10073/
Publication URL: https://www.nature.com/articles/s41467-023-41735-3
