1. F. Tosi, A. Longobardo, O. Prieto-Ballesteros, G. ChobletM5
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. For Planning and Discussion Purposes Only
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
5/16/2018
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
In-orbit
Surface
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
5/16/2018
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
5/16/2018
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
Constrain the composition of Europa’s atmosphere and potential plumes
In-orbit
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
5/16/2018
For Planning and Discussion Purposes Only

7. 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 following additional science goal can be identified:
Discrimination between water ice and clathrate hydrates
This measurement is crucial to constrain not only the surface composition, but also the formation mechanism of water plumes (cold faithful, frigid faithful, deep source). However, this discrimination is not possible by means of remote spectroscopy, due to the similar absorption features of these compounds.
An in-situ characterization is hence necessary.
Instruments to be considered: Micro-thermograivimeter, Raman spectrometer.

10. 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. Micro-thermogravimeter science goals
The VISTA (Volatile In Situ Thermogravimetry Analyzer) thermogravimeter, developed by a consortium of Italian institutes led by IAPS-INAF, has the following science goals:
Detection of volatile and dust material released by plumes (in-orbit measurement)
Discrimination between water ice and clathrate hydrates (surface measurement)
Composition of non-ice material (surface measurement)
Detection and measurement of organics abundance (surface measurement)
5/16/2018
For Planning and Discussion Purposes Only

12. VISTA Technical CharacteristicsM5
VISTA Technical Characteristics
MEU
Sensor head
S/C
Unit
Sensor Head
Sensor type
Quartz Crystal Microbalance
Resonant Frequency (MHz) 10
Mass [g] 90
Power [mW]
240 (peak); 180 (mean)
Data rate
30 bit/measurement
Operating Temperatures [K]
Sensitivity (flux)
4.4 ng cm-2 s-1
Sensitivity (abundance)
100 ppm
The MEU does not contribute to the total instrument of the mass since is shared with other sensors
5/16/2018
For Planning and Discussion Purposes Only

13. For Planning and Discussion Purposes OnlyM5
VISTA Heritage
Selected in the scientific package of MarcoPolo-R (ESA Cosmic Vision )
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.
5/16/2018
For Planning and Discussion Purposes Only

14. For Planning and Discussion Purposes OnlyM5
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
5/16/2018
For Planning and Discussion Purposes Only