REVIEW OF EXCHANGE PROCESSES ON GANYMEDE IN VIEW OF ITS PLANETARY PROTECTION CATEGORISATION

In this work, we provide a detailed review of Ganymede’s characteristics which are germain to any consideration of its planetary protection requirements. Ganymede is the largest moon in our Solar System and is the subject of one of the main science objectives of the JUICE mission to the Jupiter system. We explore the probability of the occurrence of potentially habitable zones within Ganymede at present, including those both within the deep liquid ocean and those in shallow liquid reservoirs. We consider the possible exchange processes between the surface and any putative habitats, in order to set some constraints on the planetary protection approach for this moon. As a conclusion, the “remote” versus “significant” chance of contamination will be discussed, according to our current understanding of this giant icy moon. Based on the different estimates we investigate here, it appears extremely unlikely that material will be exchanged downwards through the upper icy layer of Ganymede, thus bringing material into the ocean, over timescales consistent with the survival of microorganisms.