F. Tosi, A. Longobardo, O. Prieto-Ballesteros, G. Choblet

1. M5 PSI #4: characterize the exchange processes between the surface/ subsurface and the aqueous interior reservoirs F. Tosi, A. Longobardo, O. Prieto-Ballesteros, G. Choblet

2. PSI #4 The main goal is to assess the habitability of Europa via in situ techniques. According to the NASA Europa Lander STM, this can be performed by means of three investigations: I1 : characterize the non-ice composition of Europa’s near-surface material and determine whether there are indicators of chemical disequilibrium and other components essential for life. I2 : Determine the proximity to liquid water I3 : Detect whether Europa is active today and characterize any observable surface exchange processes For Planning and Discussion Purposes Only

3. Starting from Geochemistry (Composition) scientific goals of the EM mission listed in the Science Traceability Matrix, we adopt, for each investigation and for each scenario (in-orbit or surface) the following colour code: • Red: The additional mission element could not achieve the goal • Yellow: The additional mission element could achieve the goal, but does not bring additional information w.r.t. EM mission • Green: The additional mission element could bring substantial new science to EM mission 2. The additional information related to «green» goals is detailed and possible instruments which could perform these measurements are identified. 3. Instruments which could perform these measurements are addressed.

4. Investigation 1: non-ice materials Identify and map the distribution of non H2O-ice materials on the surface and correlate them with endogenic and exogenic features In-orbit Surface Cross correlate particle and gas measurements to constrain the ocean's pH and extent of water-rock interaction In-orbit Surface Determine the distribution and composition of salt and inorganic deposits in different geologic settings to assess the variability in transport of salts between different reservoirs Surface In-orbit Determine the distribution and composition of organic material on Europa's surface at different geologic settings to assess variability in transport of organics between different reservoirs In-orbit Surface For Planning and Discussion Purposes Only

5. Investigation 2: proximity to liquid water In-orbit Surface Constrain the salinity of the internal ocean Determine the relative abundances of key compounds to constrain the chemical conditions of the ocean In-orbit Surface Determine the composition and abundance of minerals and organics embedded in the surface material to constrain the chemical conditions of the ocean In-orbit Surface For Planning and Discussion Purposes Only

6. Investigation 3: surface activity and exchange processes Study potential plume gas composition as it relates to ocean chemistry, and the UV optical properties of any dust or hazes In-orbit Surface In-orbit Constrain the composition of Europa’s atmosphere and potential plumes Surface Determine the composition of major volatiles and key organic compounds in the atmosphere and any plumes In-orbit Surface Determine the inorganic and organic surface composition of ejected solid surface material, including from potential plumes In-orbit Surface Correlate surface units and color variations with morphology and topography of geologic structures to constrain surface–subsurface exchange processes In-orbit Surface Determine the grain size, crystallinity and distribution of water ice globally and at locations of possible recent geologic activity In-orbit Surface For Planning and Discussion Purposes Only

7. M5 Complementary science at Europa • In the case of a flying element or a descent probe that approaches Europa at heights <25 km or flying over plumes or over sites other than those already selected for the C/A of EM, an additional INMS or a thermo-gravimeter would provide measurements complementary to those carried out by MASPEX onboard EM, because the atmospheric density increases dramatically as we get closer to the surface. • This would also allow a larger coverage of plumes (if they are confirmed) and trace constituents.

8. M5 Surface science Identify and map the distribution of non H2O-ice materials on the surface and correlate them with endogenic and exogenic features. This measurement is performed by EM by means of remote UV spectrometry. A lander will give further details by means of in-situ measurement. Instruments to be considered: Micro-thermogravimeter, Raman spectrometer Constrain the salinity of the internal ocean. In-situ measurement will support the EM magnetometer Instruments to be considered: Radar Determine the grain size, crystallinity and distribution of water ice globally and at locations of possible recent geologic activity An in-situ measurement is possible only if the landing site shows a recent geologic activity. Instrument to be considered: Optical camera

9. M5 Surface science The followingadditional science goal can be identified: • Discriminationbetween water ice and clathratehydrates Thismeasurementiscrucial to constrainnotonly the surfacecomposition, butalso the formationmechanism of water plumes(coldfaithful, frigidfaithful, deep source). However, thisdiscriminationisnotpossible by means of remote spectroscopy, due to the similarabsorptionfeatures of thesecompounds. An in-situ characterizationishencenecessary. Instruments to be considered: Micro-thermograivimeter, Ramanspectrometer.

10. M5 Key measurements for PSI#4 In-situ imaging and spectroscopy Exogeneous /endogeneous ? Volatiles Ions and Neutrals Subsurface radar sounding Key instruments: Optical camera Raman Spectrometer Radar sounder INMS µ-thermogravimeter

11. M5 Micro-thermogravimeter science goals The VISTA (Volatile In Situ Thermogravimetry Analyzer) thermogravimeter, developed by a consortium of Italianinstitutes led by IAPS-INAF, has the following science goals: • Detection of volatile and dustmaterialreleased by plumes (in-orbitmeasurement) • Discriminationbetweenwater ice and clathratehydrates(surfacemeasurement) • Composition of non-icematerial(surfacemeasurement) • Detection and measurement of organicsabundance (surfacemeasurement) For Planning and Discussion Purposes Only

12. M5 VISTA Technical Characteristics The MEU does not contribute to the total instrument of the mass since is shared with other sensors For Planning and Discussion Purposes Only Sensor head MEU S/C

13. M5 VISTA Heritage Selected in the scientific package of MarcoPolo-R (ESA Cosmic Vision 2015-2025) Selected for the project «Evaluation of an In-situ Molecular Contamination Sensor for Space Use» (ITT ESA contract, in progress) Studied for Phase A of Marco Polo, MarcoPolo-R, Penetrator for JUICE Its current TRL is 5/6. For Planning and Discussion Purposes Only

14. M5 Conclusions Key measurements for PSI #4 include: non-ice materials, oceans’ salinity, water ice grain size and discrimitaion between water ice and clathrate hydrates The suggested instrumentation to achieve these goals includes: Raman spectrometer, INMS, thermogravimeter, optical camera, radar For Planning and Discussion Purposes Only