Thermal drill sampling system onboard high-velocity impactors for exploring the subsurface of Europa

The planned Europa Jupiter System Mission (EJSM) will provide a unique opportunity to place scientific instruments onto the surface of Jupiter's moon Europa in the late 2020s. After the Galileo mission, this will be a long awaited chance to have a close glimpse into some of the mysteries of this moon. Care must be taken in the choice of in-situ science that will be undertaken on the surface. We present a novel approach to deliver scientific instruments into the subsurface layers of planetary ice: A thermal drill was developed which uses heat and mechanical drilling in combination to penetrate the ice. The objective of such an instrument is to penetrate the upper layers of Europa's surface to reach zones where space weathering and Jupiter's heavy radiation have not altered potentially biogenic material that might have been brought from the depths to the surface. This paper presents the concept of the thermal drill and test results from its prototype. In the second part of the paper, we study the possibility of integrating a melting probe as a sampling system in high-velocity penetrators. The use of a melting probe in such a mission scenario gives various advantages: For example, a melting probe is less sensitive to the high decelerations of the impacting penetrators since the number of moving parts is reduced. This sampling technique would extend the operational range of an impact penetrator, allowing it to reach zones well beyond the depths where organic matter might be altered by micro-meteoroids and radiation. The paper concludes with a forecast into what kinds of instruments could be integrated into such a mission.