[P-PS02] [EE] Small Bodies: Exploration of the Asteroid Belt and the Solar System at Large

[PPS02-25] Hayabusa2 and the formation of the Solar System

*Sei-ichiro WATANABE^1,2, Hayabusa2 Science Team² (1.Division of Earth and Planetary Sciences, Graduate School of Science, Nagoya University, 2.JAXA/ISAS)

Keywords:C-type asteroid, Planetary exploration, Sample return

Explorations of small solar system bodies bring us direct and unique information about the formation and evolution of the Solar system. Asteroids may preserve accretion processes of planetesimals or pebbles, a sequence of destructive events induced by the gas-driven migration of giant planets, and hydrothermal processes on the parent bodies. After successful small-body missions like Rosetta to comet 67P/Churyumov-Gerasimenko, Dawn to Vesta and Ceres, and New Horizons to Pluto, two spacecraft Hayabusa2 and OSIRIS-REx are now traveling to dark primitive asteroids.The Hayabusa2 spacecraft journeys to a C-type near-earth asteroid (162173) Ryugu (1999 JU3) to conduct detailed remote sensing observations and return samples from the surface. The Haybusa2 spacecraft developed by Japan Aerospace Exploration Agency (JAXA) was successfully launched on 3 Dec. 2014 by the H-IIA Launch Vehicle and performed an Earth swing-by on 3 Dec. 2015 to set it on a course toward its target. The spacecraft will reach Ryugu in the summer of 2018, observe the asteroid for 18 months, and sample surface materials from up to three different locations. The samples will be delivered to the Earth in Nov.-Dec. 2020.
Ground-based observations have obtained a variety of optical reflectance spectra for Ryugu. Some reported the 0.7 μm absorption feature and steep slope in the short wavelength region, suggesting hydrated minerals. Some others obtained very flat spectra. Such variety might reflect surface chemical inhomogeneity. Through deciphering memories recorded on the asteroid, Hayabusa2 will increase our knowledge of the material mixing and transfer processes in the early solar system, mineral-water-organic interactions on planetesimals, and dynamical processes such as impact [1].
Hayabusa2 carries a sampler and four onboard remote-sensing instruments: a multi-band optical imager (ONC-T), a laser altimeter (LIDAR), a near infrared spectrometer covering 3-μm absorption band (NIRS3), and a thermal infrared imager (TIR). It also has three small rovers of MINERVA-II and a small lander MASCOT (Mobile Asteroid Surface Scout) developed by DLR in cooperation with CNES. Further, Hayabusa2 has impact experiment devices, which consist of a small carry-on impactor (SCI) excavating underground materials and a deployable camera (DCAM3) to observe the ejecta curtain. The interdisciplinary research using the data from these onboard and lander’s instruments and the analyses of returned samples is the key to the success of the mission.

[1] Tachibana et al. (2014) Geochem. J. 48, 571-587.