[P-CG18] Future missions and instrumentation for space and planetary science

[PCG18-13] Titan's seismology with Dragonfly Geophysical and Meteological package
("DraGMet")

★Invited Papers

Hiroaki Shiraishi³, Satoshi Tanaka³, *Taichi Kawamura^1,2, Takefumi Mitani³, Hideki Murakami¹⁰, Ryuhei Yamada⁴, Shunichi Kamata⁵, Jun Kimura⁶, Hiroyuki Kurokawa⁷, Kiwamu Nishida⁸, Yasuhito Sekine⁷, Takeshi Tsuji⁹, Keisuke Onodera³, Ralph Lorenz¹¹ (1.Institut de Physique du Globe de Paris, 2.Université de Paris, 3.Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, 4.The University of Aizu, Revitalization Center, 5.Faculty of Science, Hokkaido University, 6.Osaka University, 7.Earth-Life Science Institute, Tokyo Institute of Technology, 8.Earthquake Research Institute, University of Tokyo, 9.Department of Earth Resources Engineering, Kyushu University, 10.Faculty of Science and Technology, Kochi University, 11.Johns Hopkins University Applied Physics Laboratory Johns Hopkins University Applied Physics Laboratory)

Keywords:Titan, Seismology, Planetary Exploration

Dragonfly is NASA’s Titan mission selected for the 4^th New Frontier mission. The main aim of the mission is to explorer and understand the prebiotic environment of Titan. We will have a drone type spacecraft that enables us to explore multiple region, such as dunes, inter-dune regions, and plains. The spacecraft will sample and examine dozens of sites with high probabilities to find evidence of prebiotic environment. The mission is planned to be launched in 2027. The baseline mission will perform ~ 3 years of observation of Titan after the arrival and a typical observation plan is that during the Titan day time (~192h), the spacecraft will fly to the next target site and perform series of observations of the site. When we enter the Titan night time, the spacecraft will stay at the site for occasional science activities or continuous observation at the site. Dragonfly will repeat such cycle and explore several different sites on Titan.

The spacecraft is equipped with a suite of instruments that realizes geochemical, geophysical, and meteorological observations. DragMS, which is a mass spectrometer which is designed to study the organic materials in the atmosphere and Titan surface. DragMS also includes the drilling and sampling system that collects samples during the landing and observe gas and solid materials collected from Titan surface. DraGNS is Gamma Ray and Neutron spectrometer which measures light elements related to prebiotic environment (C, H, O, N) and other elements. Dragon Cam is a suite of cameras that includes cameras used for cruising and also a micro-scope camera for geochemical and geological observations. DragMet is a suite of geophysical and meteorological observations they will perform observations mainly during the night time to constrain the atmospheric condition of Titan and subsurface structure of the landing site.

Among the installed payload, the short period seismometer, which is a part of DragMet package will be provided by ISAS/JAXA. The aim of the seismometer is to perform active and passive observations during the landing and investigate the internal structure of Titan. The first experiment will be to perform active seismic observations during the drilling and sampling operation. This will enable us to probe the local and shallow structure below the lander. Such observation helps us obtain the geological context where we collect the sample which is an essential piece of information to interpret the nature of obtained samples. The second experiment is passive observations of natural seismic events. While seismicity of Titan is unknown, we expect some possible candidates of seismic sources such as tidal quakes excited by tidal stress between Saturn and Titan or cracks within the icy crust. In addition to such quakes, given that Titan has dense atmosphere, we expect seismic signals excited by atmospheric activities such as those observed on Mars. We are investigating such possibilities to propose a feasible observation scenario for the mission. In this presentation, we will discuss our activities and investigations made by the seismometer science team, which consists of expertise of icy satellites and astrobiology.