Seismic investigation of icy crust covering subsurface oceans of Europa and Ganymede: Preliminary assessment of hypothetical experiment using impactor

摘要

Jupiter's satellite Europa is believed to harbor a global ocean beneath its ice-covered surface. But the thickness of this ice, despite its significance to the habitability of this moon, is unknown: estimates range from as thin as hundreds of meters to as thick as tens of kilometers. In this paper, we investigate the feasibility of a hypothetical experiment in which the ice's thickness is measured via seismic analysis. The assumed scenario calls for a seismometer to be placed on the satellite's surface to detect the ice surface's seismic response induced by an artificial impact event. Our hypothetical experiment could be applied at Europa as well as at Ganymede. For both satellites, two impact scenarios are considered: a low-energy-impact case, in which an orbiter probe impacts the ice at the end of the mission, and a high-energy-impact case, in which a spent upper rocket stage impacts the ice upon Jupiter arrival. We find that an impactor-induced seismic investigation is a promising add-on experiment in future missions to the icy moons of Jupiter.