Europa’s icy crust may be venting ocean water into space, and a new analysis of old spacecraft data aims to pinpoint exactly where. Jupiter’s moon Europa is one of the best candidates for harbouring life beyond Earth, because a global saltwater ocean lies beneath its frozen surface. Plumes of material, possibly from that ocean, have been detected, but their sources and timing remain unknown. Two major missions—ESA’s Juice and NASA’s Europa Clipper—are heading to Jupiter, but without knowing where or when plumes erupt, their ability to sample the ocean directly is limited. This project will re-examine 85+ unanalysed datasets from the Galileo spacecraft, searching for thermal hotspots and mapping surface changes caused by plume fallout. The team will also model how Europa’s surface responds to heat, to predict when and where future observations should focus. If successful, the work will give Juice and Europa Clipper a concrete target for plume hunting, turning guesswork into a planned search. This is fundamental planetary science with no immediate practical application, but understanding Europa’s activity is a direct step toward answering whether life exists elsewhere in the Solar System.
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Jupiter’s ocean-world satellite Europa is a critical target for habitability, as evidenced by STFC Science Challenge B:4 what are the conditions for life and how widespread are they?, where Europa’s habitability importance is specifically mentioned. There is mounting evidence for Europa having plumes, which if formed from sub-surface ocean water could provide future missions a non-invasive way of sampling its potentially habitable ocean. However, where the plumes emanate from, their effect on Europa’s surface, and implications for habitability are unknown. Two missions are currently set to explore Europa: ESA’s Juice and NASA’s Europa Clipper. However, without knowing Europa’s plume source location(s) and when they might erupt, their ability to study active plumes relies on guesswork. So, our aim is to use existing data and models to better constrain Europa’s plume sources. We use two methods: direct detection (hotspots), and inferred detection (surface alteration), and in regions where endogenic activity is not observed we set upper limits on the magnitude of undetected activity. We will search for undiscovered hotspots in Galileo PhotoPolarimeter Radiometer (PPR) data because it has extensive surface coverage and limited prior analysis. We will produce surface temperature maps from each of the 85+ low-noise unanalysed PPR Europa data sets, then search these maps for evidence of statically significant hotspots. Important discoveries from Galileo data are still feasible - reanalysis of its magnetometer data found evidence of Europan plume eruption! Plume fallout is expected to be brighter (higher albedo) and less consolidated (lower thermal inertia) than Europa’s older weathered surface. By comparing derived surface temperatures to passive temperature models we will map albedo and thermal inertia. These maps will be investigated for evidence of plume fallout and other endogenic and exogenic alteration processes – distinguishable because of their characteristic alteration patterns. Finally, by modelling Europa’s surface’s response to heating we will constrain the surface’s response to vents with different temperatures and surface characteristics. By comparing these to Europa’s passive temperatures we can constrain when, where and how often studies should search its surface for hotspots. Should hotspots be observed we will constrain the magnitude of its emission with this work. The time driver is to provide Europa Clipper and Juice the most complete picture of Europa’s activity as soon as possible – so they can include it in their operational planning that is currently in development. However, we expect this work to assist all future searches for Europa’s activity.
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