Frontier Research Institute for Interdisciplinary Sciences
Tohoku University

Our final goal is to universally understand creation and evolution of habitable environments in the space and atmosphere surrounding planets.

Our current scope is the icy bodies in our solar system, at which liquid water ‘subsurface ocean’ is confirmed underneath solid icy surface. The extra-terrestrial life like deep sea creatures at Earth potentially exists in the subsurface ocean. In 2030s, we are going to explore space and surface environments at Jupiter’s icy moons ‘Ganymede’ and ‘Europa’ based on highly precise ‘in-situ’ measurement with spacecraft developed in international collaboration with JAXA and ESA. Creation and evolution of the subsurface ocean will be uncovered by our laboratory experiment for the icy body’s space environment in comparison with the in-situ spacecraft observation.

The key for our goal is the space plasma surrounding the icy body. The space plasma is accelerated by electromagnetic energy deposited in intrinsic magnetic field and rotation of planet. The energetic plasma irradiates materials of the icy body’s surface. Chemical and physical alterations on the surface materials are driven by the irradiation, which is referred to as the ‘space weathering’. The space weathering slowly progresses on timescales up to 100s Mega years.

The icy body also has the intrinsic magnetic field that is generate by fluid dynamics in the interior. The icy body magnetic field reflects the space plasma, leading to dependence of the space weathering on magnetic field strength on the surface. Based on laboratory experiment for the space weathering in comparison with the spacecraft exploration, we estimate the age of magnetic field that constrains differentiation of the icy body interior including development and evolution of the subsurface ocean.