Japan Geoscience Union Meeting 2019

Presentation information

[E] Oral

P (Space and Planetary Sciences ) » P-PS Planetary Sciences

[P-PS02] Regolith Science

Wed. May 29, 2019 3:30 PM - 5:00 PM A01 (TOKYO BAY MAKUHARI HALL)

convener:Koji Wada(Planetary Exploration Research Center, Chiba Institute of Technology), Akiko Nakamura(Graduate School of Science, Kobe University), Patrick Michel(Observatoire De La Cote D'Azur), Kevin John Walsh(Southwest Research Institute Boulder), Chairperson:Akiko Nakamura(Graduate School of Science, Kobe University)

4:15 PM - 4:30 PM

[PPS02-10] In-Situ Investigation of Asteroid (162173) Ryugu by the Hayabusa2 MASCOT Lander

★Invited Papers

*Hajime Yano1, Tra-Mi Ho2, Ralf Jaumann3, Jean-Pierre Bibring4, Karl-Heinz Glassmeier5, Matthias Grott3, David Hercik5, Jens Biele6, Maximilian Hamm3, Nicole Schmitz3, Stefanus Schröder3, Katharina Otto3, Christian Krause6, Laurence Lorda7, Aurelie Moussi-Soffys7, Cedric Pilorget4, Vincent Hamm4, Lucie Riu1, Tatsuaki Okada1, Naoya Sakatani1, Josef Reill8, Kaname Sasaki2, Markus Schlotterer2, Yuichi Tsuda1, Stephan Ulamec6, Friederike Wolff8, Patrick Michel9, Marco Delbo9, Kazunori Ogawa10, Hiroki Senshu11, Tetsuo Yoshimitsu1, Frank Preusker3, Frank Scholten3, Stephan Elgner3, Stefano Mottola3, Ekkehard Kührt3, Takanao Saiki1, Yuya Mimasu1 (1.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan, , 2.German Aerospace Center DLR Bremen, Bremen, Germany, 3.German Aerospace Center, Berlin, Germany, 4.Univ. de Paris Sud-Orsay, IAS, Orsay, France, 5.TU Braunschweig, Braunschweig, Germany, 6.German Aerospace Center DLR Cologne, Cologne, Germany, 7.National Centre for Space Studies, CNES, Toulouse, France, 8.German Aerospace Center, DLR, Oberpfaffenhofen, Germany, 9.Université Côte d’Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France, 10.Department of Planetology, Graduate School of Science, Kobe University, Kobe, Japan, 11.Planetary Exploration Research Center, Chiba Institute of Technology, Narashino, Japan)

Keywords:Ryugu, Hayabusa2, Asteroid Surface, Lander, Carbonaceous Chondrites, High Porosity

After a journey of almost four years to the C-type asteroid (162173) Ryugu, the MASCOT lander of the Hayabusa2 mission was delivered to the asteroid’s surface on October 3rd in 2018 and successfully performed in situ investigations. MASCOT was released from the mother spacecraft at an altitude of 41 m and came to rest on the surface at a site located at 22.31±0.05°S, 317.16±0.05°E. MASCOT observed the surface for a full day-night cycle using its four science instruments until batteries ran out after 17h and 7min. The payload consisting of a wide angle camera (MASCAM), an imaging IR spectrometer (MicrOmega), a multi-channel radiometer (MARA), and a magnetometer (MasMAG) provided a wealth of data which helped to characterize the asteroid’s surface down to millimeter scale. MasCAM images revealed a surface dominated by rocks and boulders without showing fine-grained material. Boulders appeared either bright with smooth faces and sharp edges or dark with cauliflower-like crumbly surfaces. Inclusions observed in high-resolution images showed that rocks had strong similarities with carbonaceous chondrites. Temperatures of a ~60 cm diameter rock that have been measured in situ, were found to be consistent with a thermal inertia of 282(+93, -35) J m-2 K-1 s-1/2, much lower than anticipated when compared to samples in our meteorite collections. This indicated that rocks on Ryugu were highly porous and likely very friable. The remnant magnetization of Ryugu's surface material on scales larger than 1 m was estimated to be lower than 3·10-6 Am2/kg (the measurement limit of MasMAG). A preliminary analysis of the induction effect in Ryugu caused by the variation in the solar wind magnetic field revealed significantly high electrical conductivity (of the order 1 S/m).