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M Matsuoka

Publications and source records attributed to M Matsuoka.

7 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

Observations of Phobos and Deimos with SpeX at NASA Infrared Telescope Facility

We measured near-infrared (NIR) reflectance spectra of Phobos and Deimos, using the prism (0.7–2.52 μm) and long-wavelength cross dispersed (LXD: 1.9–4.2 μm) modes of NASA Infrared Telescope Facility (IRTF)’s SpeX instrument. The goal of this study is to investigate the surface composition of Phobos and Deimos and search for any mineralogical absorption signatures that may be present on their surfaces, especially in the LXD spectral range. Prism spectra of Phobos showed significant slope variation at shorter wavelengths (λ <1.3 μm), which indicates surface heterogeneity possibly due to regolith’s composition and grain size, and/or space weathering. Deimos’ prism spectra were found to be consistent with the more red-sloped prism spectra of Phobos. The measured LXD spectra of Deimos revealed evidence of hydration with 3-μm band depths at 2.90 μm of 4–5%. The 3-μm band in Deimos could be attributed to exogenic sources such as solar wind implantation or OH-bearingimpactors, or to an endogenic source and the presence of carbonaceous material on its surface. Phobos’ andDeimos’ prism and LXD spectra, however, show no indications for absorption signatures of mafic silicates (i.e.,pyroxene, olivine), organics nor carbonates.

D Takir↗
NASA NTRS2021

Thermally Altered Subsurface Material of Asteroid 162173 Ryugu

Studies of meteorite analysis and theoretical modeling have indicated the possibility that some carbonaceous near-Earth asteroids are thermally altered due to radiative heating during close approaches to the Sun in addition to parent body processes (Nakamura, 2005; Marchi et al., 2009; Chaumard et al., 2012). In April 2019, the Hayabusa2 mission successfully completed an artificial impact experiment on the carbonaceous near-Earth asteroid 162173 Ryugu (Arakawa et al., 2020), which provided an opportunity to investigate the effects of radiative heating through the exposed subsurface material. Here we report observations of the Ryugu’s subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Spectra of the subsurface material exhibit a slightly stronger and peak-shifted hydroxyl absorption feature compared to that observed for the surface, indicating that space weathering and/or radiative heating caused a subtle change in the spectrum of Ryugu surface. However, the shape of the absorption feature still suggests that the subsurface material experienced heating above 300 ˚C similar to the surface. In contrast, our thermal modeling shows that radiative heating does not increase the subsurface temperature at 1 m depth above 200 ˚C even if the semimajor axis is reduced down to 0.344 au. This supports that the Ryugu material would have been preferentially altered due to radiogenic and/or impact heating on the parent body rather than radiative heating.

Asteroids↗
NASA NTRS2020

Characterization of the Ryugu Surface By Means Of the Variability of the Near-Infrared Spectral Slope in NIRS3 Data

The Near-Earth Asteroid 162173 Ryugu (1999 JU3) was investigated by the JAXA Hayabusa2 mission from June 2018 to November 2019. The data acquired by NIRS3 spectrometer revealed a dark surface with a positive near-infrared spectral slope. In this work we investigated the spectral slope variations across the Ryugu surface, providing information about physical/chemical properties of the surface. We analysed the calibrated, thermally and photometrically corrected NIRS3 data and we estimated the mean value of spectral slope between 1.9 μm and 2.5 μm, corresponding to 0.163. Starting from the mean value of slope and moving in step of 1 standard deviation (0.022), we defined 9 “families of slope”, the Low-Red-Slope families (LR1, LR2 and LR3) and the High-Red-Sloped families (HR1, HR2, HR3, HR4, HR5, HR6). The mean values of some spectral parameters were estimated for each family, such as the reflectance factor at 1.9 μm, the spectral slope, the depth of bands at 2.7 μm and at 2.8 μm. A progressive spectral reddening, darkening and weakening/narrowing of OH bands is observed moving from the LR families to the HR families. We concluded that the spectral variability observed among families is the resulting contribution of the thermal metamorphism experienced by Ryugu after the catastrophic disruption of its parent body and space weathering processes that occurred on airless bodies as Ryugu, such as impact cratering and solar wind irradiation. As a consequence, the HR1, LR1, LR2 and LR3 families, corresponding to equatorial ridge and crater rims, are the less altered regions on Ryugu surface, which experienced the minor alteration and OH devolatilization; the HR2, HR3, HR4, HR5 families, coincident with floors and walls of impact craters, are the most altered areas, result of the three processes occurred on Ryugu. The strong reddening of the HR6 family (coincident with Ejima Saxum) is likely due to the fine-sized material covering the large boulder.

Ryugu↗
NASA NTRSDate not supplied

A Study of the Curation Protocol by Sample Analysis Working Team (SAWT) in Martian Moons eXploration (MMX) Project

Japan Aerospace Exploration Agency (JAXA) will launch a spacecraft in 2024 for a sample return mission from Phobos (Martian Moons eXploration: MMX). The major scientific goals of MMX are to constrain (1) the origin of Phobos and Deimos and (2) the evolution of the Mars-moon system [1]. The touchdown operations are planned to be performed twice at different landing sites on the Phobos surface to collect > 10 g of the surface materials [2]. After the return to the Earth, the Phobos samples will be collected from the individual sample canisters and introduced to the clean chamber installed at ISAS (Institute of Space and Astronautical Science). The Sample Analysis Working Team (SAWT) of MMX designed the procedure of Phobos sample analysis mainly conducted by the initial analysis teams [3]. For the next step, the SAWT will define the procedure of the curation process (mostly non-destructive analysis) of the Phobos samples, which will be presented here. The protocols of the Phobos sample curation is illustrated in figure 1. First, the headspace gas from the sample container will be collected during the Quick Analysis phase. The Quick Analysis will be operated by the sampler and curation teams in ISAS/JAXA. The terrestrial leak and contamination from the sampling systems will be tested using a quadrupole mass spectrometer equipped with a gas sampling system. Second, the bulk Phobos sample will be observed in the clean chamber under purified-N2 gas with an ambient condition (Pre-basic Characterization). This phase will be operated by the curation team in ISAS/JAXA and the instrument team of the MMX mission. The consistency between the data from the instruments in the clean chamber and the spacecraft will then be evaluated. Subsequently, the curation will distribute the small amount of Phobos samples to the Initial analysis team of MMX to conduct the "Preliminary Examination". The objectives of the preliminary examination are to provide (1) feedback on the subsequent sample allocation process, (2) preliminary scientific results that will address parts of MMX mission goals, and (3) evaluation of the sampling system and terrestrial alteration on Phobos samples. Because multiple models are proposed for the origin of Phobos [1] (e.g., giant impact, the capture of asteroids), the chemical and mineralogical characteristics of Phobos must be assessed before the allocation of the samples to the individual initial analysis teams. Simultaneously, the curation team in JAXA will observe the individual grains and aliquots of the samples in the clean chamber (Basic Characterization).

R Fukai↗
NASA NTRSDate not supplied

Curation protocol of Phobos sample returned by the Martian Moon Exploration (MMX)

The Martian Moons Exploration (MMX) aims to return the regolith samples from the Martian moon, Phobos. After the topographic and spectroscopic observation, the spacecraft will land on the surface of Phobos to conduct the sampling operation[1–2]. Pneumatic and coring samplers will collect ≥10 g Phobos grains from two different sites. The collected samples will be retrieved from the capsule and transferred to the curation facility in 2029.

R Fukai↗