Jun Kimura

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Osaka University | Handai · Department of Earth and Space Science

We present near-infrared high-dispersion spectroscopic observations of Europa using the Infrared Camera and Spectrograph (IRCS) onboard the Subaru Telescope, seeking direct evidence of water plumes on Europa and exploring spatial variations in plume activity. Using the high spectral/spatial resolution and sensitivity of Subaru/IRCS, our observation...

We present near-infrared high-dispersion spectroscopic observations of Europa using the Infrared Camera and Spectrograph (IRCS) onboard the Subaru Telescope, seeking direct evidence of water plumes on Europa and exploring spatial variations in plume activity. Using high spectral/spatial resolution and sensitivity of Subaru/IRCS, our observations ha...

The JUpiter ICy moons Explorer (JUICE) of ESA was launched on 14 April 2023 and will arrive at Jupiter and its moons in July 2031. In this review article, we describe how JUICE will investigate the interior of the three icy Galilean moons, Ganymede, Callisto and Europa, during its Jupiter orbital tour and the final orbital phase around Ganymede. De...

During the Galileo spacecraft’s flyby of Europa, magnetic field measurements detected an inductive signal due to the response of Europa’s interior conductors to temporal fluctuations in the Jovian magnetic field. In contrast, no signatures of intrinsic magnetic field originating from the dynamo motion in the metallic core were acquired. These measu...

The Wispy Terrain is the region of chasmata characterized by quasi-parallel fault systems, formed by extensional and shear stresses of the icy crust of Dione, a moon of Saturn. Besides the basic, satellite-scale geological mapping and very general definition of the phenomenon, only a few studies focus on the Wispy Terrain and its chasmata from the...

In the tenuous atmospheric bodies of our solar system, space weathering on the celestial surface is an important process for its chemical and physical evolution and ambient environment on timescales of celestial evolution. Space plasma is a dominant energy and material source for space weathering. Plasma irradiation experiment in the laboratory is...

In the tenuous atmospheric bodies of our solar system, space weathering on the celestial surface is an important process for its chemical and physical evolution and ambient environment on timescales of celestial evolution. Space plasma is a dominant energy and material source for space weathering. Plasma irradiation experiment in the laboratory is...

The first images of Jupiter's moon Europa from the Voyager missions sparked the curiosity about the lineament system appearing at the surface. Curiosity quickly turned into profound interest, following the discovery of its subsurface ocean, which may harbour life below the thick ice crust. This study revisits Europa and reinvestigates its surface u...

The Jupiter Icy Moons Explorer (JUICE) is a science mission led by the European Space Agency, being developed for launch in 2022. The Ganymede Laser Altimeter (GALA) is an instrument onboard JUICE whose main scientific goals are to understand ice tectonics based on topographic data, the subsurface structure by measuring tidal response, and small-sc...

The difference between the inactive surface of Mimas and the active surface of Enceladus is puzzling. We investigate the conditions under which the both have a thick subsurface ocean and the thermal lithosphere of Mimas is thicker than that of Enceladus by using a one-dimensional simulation of thermal evolution. We adopt the initial core temperatur...

The difference between the inactive surface of Mimas and the active surface of Enceladus is puzzling. We investigate the conditions under which both have a thick subsurface ocean and the thermal lithosphere of Mimas is thicker than that of Enceladus by using a one-dimensional simulation of thermal evolution. We adopt the initial core temperature, i...

We explore the long-term evolution of Pluto’s subsurface ocean in the absence of an insulating clathrate hydrate layer. Numerical simulations of the thermal history of the interior are performed using a 1D model assuming Pluto was initially differentiated into an outer hydrosphere (H2O shell) and an inner rocky core. We consider two end-member init...

The Ganymede Laser Altimeter (GALA) is one of the ten scientific instruments selected for the Jupiter Icy Moons Explorer (JUICE) mission currently implemented under responsibility of the European Space Agency (ESA). JUICE is scheduled for launch in mid 2022; arrival at Jupiter will be by end of 2029 with the nominal science mission—including close...

In this review, we describe some of the central philosophical issues facing origins-of-life research and provide a targeted history of the developments that have led to the multidisciplinary field of origins-of-life studies. We outline these issues and developments to guide researchers and students from all fields. With respect to philosophy, we pr...

In this review, we describe some of the central philosophical issues facing origins-of-life research and provide a targeted history of the developments that have led to the multidisciplinary field of origins-of-life studies. We outline these issues and developments to guide researchers and students from all fields. With respect to philosophy, we pr...

Many icy Solar System bodies possess subsurface oceans. On Pluto, Sputnik Planitia’s location near the equator suggests the presence of a subsurface ocean and a locally thinned ice shell. To maintain an ocean, Pluto needs to retain heat inside. On the other hand, to maintain large variations in its thickness, Pluto’s ice shell needs to be cold. Her...

The near-Earth carbonaceous asteroid 162173 Ryugu is thought to have been produced from a parent body that contained water ice and organic molecules. The Hayabusa2 spacecraft has obtained global multi-color images of Ryugu. Geomorphological features present include a circum-equatorial ridge, east/west dichotomy, high boulder abundances across the e...

The near-Earth carbonaceous asteroid 162173 Ryugu is thought to have been produced from a parent body that contained water ice and organic molecules. The Hayabusa2 spacecraft has obtained global multicolor images of Ryugu. Geomorphological features present include a circum-equatorial ridge, east-west dichotomy, high boulder abundances across the en...

GALA (GAnymede Laser Altimeter) is one of the payload instruments of the JUICE (JUpiter ICy moons Explorer) project to be launched in 2022 to the Jovian icy moons Ganymede, Europa, and Callisto. GALA is developed through an international collaboration between Germany, Japan, Switzerland, and Spain. With the performance model of GALA, we have sought...

GALA (GAnymede Laser Altimeter) is one of the payload instruments of the JUICE (JUpiter ICy moons Explorer) project to be launched in 2022 to the Jovian icy moons Ganymede, Europa, and Callisto. GALA is developed through an international collaboration between Germany, Japan, Switzerland, and Spain. With the performance model of GALA, we have sought...

Jupiter’s moon Europa may have an internal ocean of liquid water, along with the chemical compounds and energy source that life requires. Europa is covered by the solid icy shell, similar to other solid bodies in the outer solar system. The solid icy shell fractures and deforms creating cracks, ridges, and bands in relatively a recent period. Galil...

A global classification map of lunar absorption spectra is developed under unified classification criteria by applying the K-means and ISODATA unsupervised classification methods. The spectra were obtained by the Spectral Profiler (SP) onboard the Kaguya (SELENE) lunar orbiter spacecraft. The spectra are mostly categorized into seven spectral group...

The formation and orbital evolution of Saturn's inner mid-sized moons are still debated. The most puzzling aspects are 1) how the Tethys-Dione pair and the Mimas-Enceladus pair passed through their strong 3:2 mean-motion resonances during the tidal orbital evolution, and 2) the current strong heat flow from Enceladus, which is a few orders of magni...

The formation and orbital evolution of Saturn's inner mid-sized moons are still debated. The most puzzling aspects are 1) how the Tethys-Dione pair and the Mimas-Enceladus pair passed through their strong 3:2 mean-motion resonances during the tidal orbital evolution, and 2) the current strong heat flow from Enceladus, which is a few orders of magni...

Laser altimetry is a powerful tool for addressing the major objectives of planetary physics and geodesy, and have been applied in planetary explorations of the Moon, Mars, Mercury, and the asteroids Eros, and Itokawa. The JUpiter Icy Moons Explorer (JUICE), led by European Space Agency (ESA), has started development to explore the emergence of habi...

Laser altimetry is a powerful tool for addressing the major objectives of planetary physics and geodesy, and have been applied in planetary explorations of the Moon, Mars, Mercury, and the asteroids Eros, and Itokawa. The JUpiter Icy Moons Explorer (JUICE), led by European Space Agency (ESA), has started development to explore the emergence of habi...

The Ganymede Laser Altimeter (GALA) is one of the instruments selected for the first ESA large class mission JUICE. The scientific goals of the GALA instrument cover a wide range of questions of geology, geophysics and geodesy. Here we will present an overview on the scientific goals as well as on the instrument baseline design concept and the curr...

Tidal deformation of icy satellites provides crucial information on their subsurface structures. In this study, we investigate the parameter dependence of the tidal displacement and potential Love numbers (i.e., h2 and k2, respectively) of Ganymede. Our results indicate that Love numbers for Ganymede models without a subsurface ocean are not necess...

Contents 1. Introduction 1.1. A workshop and this document 1.2. Framing origins of life science 1.2.1. What do we mean by the origins of life (OoL)? 1.2.2. Defining life 1.2.3. How should we characterize approaches to OoL science? 1.2.4. One path to life or many? 2. A Strategy for Origins of Life Research 2.1. Outcomes—key questions and investigati...

A reasonable basis for future astronomical investigations of exoplanets lies in our best knowledge of the planets and satellites in the Solar System. Solar System bodies exhibit a wide variety of surface environments, even including potential habitable conditions beyond Earth, and it is essential to know how they can be characterized from outside t...

Enceladus is the only icy satellite known to exhibits on-going geological activity of water-rich plumes derived from the interior ocean. Here, we propose a sample return and in-situ measurement mission for Enceladus' plume materials. Depending on the cost, mission duration, and propulsion system, we propose three types of missions to Enceladus...

We have discovered that Europa, Ganymede and Callisto are bright around 1.5 {\mu}m even when not directly lit by sunlight, based on observations from the Hubble Space Telescope and the Subaru Telescope. The observations were conducted with non-sidereal tracking on Jupiter outside of the field of view to reduce the stray light subtraction uncertaint...

The Hayabusa-2 LIDAR is designed for safe navigation of the spacecraft. The altimetry data are also served for scientific studies of asteroid 1999JU3.

JUICE (Jupiter Icy Moon Explorer) is the ESA's first large-class mission of cosmic vision 2015-2025 program.

Hayabusa-2 is the second asteroid mission of Japan to be launched between 2014 and 2015. LIDAR is one of five instruments onboard Hayabusa-2, and measures altitudes of the spacecraft from a surface of the asteroid, 1999JU3, by taking a time of flight of laser pulse. LIDAR is a part of attitude and orbit control subsystem and is designed for navigat...

Range data taken by Hayabusa-2 LIDAR are scientifically important for analysis of the shape, mass, and surface properties of the asteroid.

We report updated status of the SELENE-2 project and some progress of development of technological aspect of the system and instruments on board.

We propose a new hypothesis for the formation of the conductive core and the surface grooved terrains on Ganymede. Numerical simulations for the interior thermal history are performed assuming that the primordial rocky core was initially hydrated. The primordial core is heated by long-lived radiogenic isotopes and becomes dehydrated if the temperat...

We report on the updated status of investigation and development of candidate instruments onboard the SELENE-2 lunar landing mission.

EJSM (Europa Jupiter System Mission) is a planned Jovian system mission with three spacecraft aiming at coordinated observations of the Jovian satellites especially Europa and the magnetosphere, atmosphere and interior of Jupiter. It was formerly called "Laplace" mission. In October 2007, it was selected as one of future ESA scientific missions Cos...

The small value of the moment of inertia factor and the strong intrinsic magnetic field observed for Ganymede are consistent with a highly differentiated interior with a conductive dense core. The Gany-mede's surface is commonly divided into two units, termed dark terrain and bright terrain. The latter, or grooved terrain, has been interpreted as g...

Despite Jovian moon Ganymede and Callisto have similar size and bulk density, their interiors are geo-detically estimated to be quite different. We propose a new hypothesis to create the interior dichotomy by focusing on a dehydration of primitive hydrous rock and metal mixed core. Numerical simulations for the moons' thermal history are performed...

Iapetus, one of the saturnian moons, has an extreme albedo contrast between the leading and trailing hemispheres. The origin of this albedo dichotomy has led to several hypotheses, however it remains controversial. To clarify the origin of the dichotomy, the key approach is to investigate the detailed distribution of the dark material. Recent studi...

Japanese lunar lander, 'SELENE-II' is being planned as a successor to 'Kaguya'. SELENE-II science mission team has been actively working to maximize the science gain. In this presentation we report the current status of the science instruments and scenario.

Unraveling the timing and duration of mare volcanism on the Moon is essential for understanding its thermal evolution. The end of mare volcanism is poorly constrained, because mare basalts are incompletely sampled. In this study, employing SELENE (Kaguya) high-resolution images, we performed new crater size-frequency measurements for 49 young mare...

Age determinations of lunar mare basalts are essential for understanding the thermal evolution of the Moon. In this study, we performed new crater size-frequency measurements in mare deposits in the central region of the northern farside, consisting of Lacus Luxuriae, Buys-Ballot, Campbell, and Kohlschütter, using high-resolution images obtained by...

In the future Jupiter system study, Coordinated observation of Jovian magnetosphere is one of the important targets of the mission in addition to icy satellites, atmosphere, and interior of Jupiter. JAXA will take a role on the magnetosphere spinner JMO (Jupiter Magnetospheric Orbiter), in addition to JGO (Jupiter Ganymede Orbiter) by ESA and JEO (...

The Ganymede's interior appears to be clearly differentiated and has a metallic core, judging from the gravity and magnetic field measurements. However processes and timing of the internal differentiation including the core formation are highly unclear. Also, origin of different internal state of Callisto which has larger moment of inertia factor c...

The state of knowledge about the structure and composition of icy satellite interiors has been significantly extended by combining direct measurements from spacecraft, laboratory experiments, and theoretical modeling. The existence of potentially habitable liquid water reservoirs on icy satellites is dependent on the radiogenic heating of the rock...

EJSM (Europa Jupiter System Mission) is an international Jovian system mission with three spacecraft. Coordinated observation of Jovian magnetosphere is one of the important targets of the mission in addition to icy satellites, atmosphere, and the interior of Jupiter. JAXA will take a role on the magnetosphere spinner JMO (Jupiter Magnetospheric Or...

Dating of lunar mare basalts is necessary for understanding the volcanic history of the Moon. Here we performed new crater counts in mare deposits on the farside and in the Orientale region, using new images obtained by SELENE Terrain Camera.

Abstract— Using the Terrain Camera onboard the Japanese lunar explorer, SELENE (Kaguya), we obtained new high-resolution images of the 22-kilometer-diameter lunar crater Giordano Bruno. Based on crater size-frequency measurements of small craters (<200 m in diameter) superposed on its continuous ejecta, the formation age of Giordano Bruno is estima...

Japanese lunar orbiter 'Kaguya' and other recent remote sensing missions have served various types of high precision and high resolution lunar surface maps such as chemical abundance, topography, mineral, magnetic field and gravity field. The next main science target is to research radial variation of the lunar interior by both geological and geoph...

Accurate estimates of the duration and volume of extrusive volcanism of the Moon are essential for understanding the lunar thermal evolution. Here, using new high-resolution images obtained by the SELENE Terrain Camera, we determined the thicknesses and ages of basalts in Mare Moscoviense, one of the most prominent mare deposits on the farside. Mar...

Ganymede has an intrinsic magnetic field which is generally considered to originate from a self-excited dynamo in the metallic core. Driving of the dynamo depends critically on the satellite's thermal state and internal structure. However, the inferred structure based on gravity data alone has a large uncertainty, and this makes the possibility of...

We investigate ages and thicknesses of mare basalts in Mare Moscoviense, which is in the northern hemisphere of the lunar farside, using high-resolution images and digital terrain models (DTMs) obtained by SELENE Terrain Camera (TC).

LAPLACE (ESA-JAXA joint mission for the Jovian system) was selected as one of future ESA scientific missions Cosmic Vision in October 2007. LAPLACE is a mission with three spacecrafts aiming at coordinated observations of Jovian satellites and the magnetosphere, atmosphere and interior of Jupiter. An orbiter around Europa or Ganymede is involved. T...

We examine means for driving hydrothermal activity in extraterrestrial oceans on planets and satellites of less than one Earth mass, with implications for sustaining a low level of biological activity over geological timescales. Assuming ocean planets have olivine-dominated lithospheres, a model for cooling-induced thermal cracking shows how variat...

Our objective is to discriminate the volcanic products on Mars from their thermal properties. We report on a thermal survey of volcanic soils in Japan. Heat conduction alone does not explain all observations. Other sources of heat are suspected.

A stress history in the ice shell of Europa is presented. Europa's surface is ubiquitous in extensional tectonic features such as banded terrains. These surface features suggest that the surface may have been fractured and extended due to tensional stress, and various origins for such stresses have been proposed. We have focused on the solidificati...

Ganymede has a intrinsic magnetic field which is generally considered to be originated by self-excited dynamo in the metallic core. The driving of dynamo depends critically on the thermal state and internal structure. However, inferred structure based on gravity data has large uncertainty and this makes the possibility of dynamo activity unclear; v...

Most eminent feature of tectonic activity on the icy satellites is extensional signatures, which have been formed by tensional stress. The examples are band-shaped terrain on Europa, and groove on Ganymede. Various origins for the stress have been discussed. The plausible candidates are solid state convection, tidal deformation, and volume change a...

Voyager and Galileo images demonstrate that most of the major icy satellites have the extensional tectonic features. It has been thought that such tectonic features formed due to the surface exten- sional stress. In various sources of stress considered, contribution of the stress due to volume change accompanied by phase change is greatly important...