1. Thermogravimetry: a technique for planetary in-situ missions A. Longobardo 1,F. Dirri 2, E. Palomba 1, A. Zinzi 3, E. Zampetti 4, S. Pantalei 4, D. Biondi 1, B. Saggin 5, A.Bearzotti 4 and A. Macagnano 4 1 IAPS-INAF, Via Fosso del Cavaliere 100, 00133 Rome, Italy 2 Dipartimento di Fisica, Università La Sapienza, Rome, Italy 3 DISAM, Università Parthenope, Naples, Italy 4 IMM-CNR, Rome, Italy 5 Politecnico di Milano, Milan, Italy

2. Outline i.Introduction to Thermogravimetry ii.Planetary applications iii.The VISTA project iv.Laboratory measurements v.Conclusions 23/10/2015EPSC 2012, Madrid2

3. Basic principles Thermogravimetry is a widely used technique to study absorption, sublimation and condensation processes. The instrument core is a Piezoelectric Crystal Microbalance (PCM), whose oscillation frequency increases at decreasing deposited mass: once the material is deposited onto the sensor it is possible to measure the amount of weight change as a function of increasing temperature due to the release of more volatile species. The temperature is increased by an appropriate heater. Abundance volatile compound Composition volatile compound 23/10/2015EPSC 2012, Madrid3

4. Application fields Detection and analysis of volatiles compounds in the studied samples, i.e. adsorbed/included in the molecular structure, or in the studied environment Analysis of condensable species, i.e. discrimination between different phases (gas/liquid/solid). The Thermo-Gravimetric Analysis (TGA) can be performed in two temperature regimes, depending on the purpose: ACT (Ambient to Cryogenic Temperatures Regime): <300 K AHT (Ambient to High Temperatures Regime): >300 K 23/10/2015EPSC 2012, Madrid4

5. Techniques for volatile measurements Attenuated Total Reflectance (ATR) - mass not lower than 200 g - power of few watts required Gas Cromatography/Mass Spectroscopy (GC-MS) /  GC-MS - instrument size of cm 3 - problems about interface between GC and MS ThermoGravimetric Analysis (TGA) /  TGA - low mass (25 g) - low size (cm 3 ) - low requested power (<1 W) 23/10/2015EPSC 2012, Madrid5

6. Outline i.Introduction to Thermogravimetry ii.Planetary applications iii.The VISTA project iv.Laboratory measurements v.Conclusions 23/10/2015EPSC 2012, Madrid6

7. Moon Water ice detection Measurement of water, organics and other volatiles content in the lunar regolith Analysis of electrical properties of regolith Scientific goals in a lunar lander scenario 23/10/2015EPSC 2012, Madrid7

8. Asteroids and comets Measurement of water and organic content in the asteroid regolith (asteroid taxonomy) Detection of cometary activity (measuring flux and dust/ice ratio) Scientific goals in a in-situ mission on asteroids or comets 23/10/2015EPSC 2012, Madrid8

9. Icy satellites Discrimination between water ice and clathate hydrates (not possible by means of spectral analysis) Determination of non-ice materials composition (solphates, carbonates, H 2 O 2 ), characterised by different sublimation temperatures Detection of possible organic presence Scientific goals in a in-situ mission on a icy satellite (e.g. Europa and Ganimede) 23/10/2015EPSC 2012, Madrid9

10. Mars Measurement of water frost point, i.e. relative humidity Detection of possible ice falls Measurement of dust settling rate Measurement of water, organics and carbonates content in the Martian dust (related to habitability of the planet) Scientific goals in a martian lander scenario 23/10/2015EPSC 2012, Madrid10

11. Venus Scientific goals in a aerostatic balloon mission on Venus Dew point (i.e. partial pressure) measurement of cloud condensable species Discrimination of volatile and refractory species in aerosols Analysis of areosol electrical properties 23/10/2015EPSC 2012, Madrid11

12. Titan Scientific goals in a aerostatic balloon mission on Titan Measurement of methan dew point (i.e. mixing ratio) Measurement of organics content (e.g. ethane, acetylene, benzene) in cloud aerosols (possible thanks to their different volatility and partial pressure) 23/10/2015EPSC 2012, Madrid12

13. Outline i.Introduction to Thermogravimetry ii.Planetary applications iii.The VISTA project iv.Laboratory measurements v.Conclusions 23/10/2015EPSC 2012, Madrid13

14. Volatile In-Situ Thermogravimetry Analyser VISTA is the thermogravimeter developed by a consortium of Italian institutes, led by IAPS-INAF and coordinated by Dr. Ernesto Palomba. Light (25 grams) Small (2x2x3 cm 3 ) Low power-consuming (60 mW for  T=60° K in vacuum) High sensitivity (10-100 ppm) 23/10/2015EPSC 2012, Madrid14

15. Instrument concept VISTA has a heater and a thermistor integrated onto the crystal. The thermistor can act as additional heater, in parallel to the other heater. In this configuration the required voltage to obtain a certain  T decreases of 50%. Simulation: V=1 V, I=50 mA P=50 mW in air 23/10/2015EPSC 2012, Madrid15

16. The lunar version: MOVIDA MOon Volatile, Ice and Dust Analyser Legend Lunar surface Capacitor Microbalance Dust particle The microbalance is placed inside a capacitor held at a voltage  V. Dust particles passing through the capacitor will deposit on the PCM in a time t depending on their charge-to-mass ratio q/m: q/m= 2/(  V t 2) 23/10/2015EPSC 2012, Madrid16

17. VISTA and ESA Cosmic Vision Different VISTA configurations have been studied for Phase A of the following ESA Cosmic Vision (2015-2025) missions: MARCO POLO Target: primitive asteroid MARCOPOLO-R Target: primitive asteroid Penetrator for EJSM Target: Europa and Ganimede 23/10/2015EPSC 2012, Madrid17

18. Outline i.Introduction to Thermogravimetry ii.Planetary applications iii.The VISTA project iv.Laboratory measurements v.Conclusions 23/10/2015EPSC 2012, Madrid18

19. Water desorption from clay (1) The mass of a clay sample has been measured 1.Before the controlled hydration 2.After the controlled hydration 3.After the  TGA In the two performed tests, the TGA measures show a very good agreeement between the amount of water absorbed from clay during its hydration and the amount of released water after the heating (Zinzi et al., Sensor and Actuators A, 2011). Controlled hydration camera 23/10/2015EPSC 2012, Madrid19

20. Water desorption from clay (2) Three kinds of experiments performed, differing on humid flux exposure time Exposition time (hours) Adsorbed water (% wt.) Desorbed water (% wt.) Measure 133.0 ± 0.22.5 ± 0.2 Measure 2162.0 ± 0.21.8 ± 0.2 Measure 315.5 ± 0.2 Average6.73.5 ± 0.23.3 ± 0.2 No dependence on exposure time Images from Zinzi et al., Sensor and Actuators A, 2011 23/10/2015EPSC 2012, Madrid20

21. 23/10/2015EPSC 2012, Madrid Enthalpy of sublimation of adipic acid in vacuum (1) Adipic acid has been heated at different temperatures and hence deposited on a cold PCM (T PCM = -25°C) 21

22. 23/10/2015EPSC 2012, Madrid Enthalpy of sublimation of adipic acid in vacuum (1) Adipic acid has been heated at different temperatures and hence deposited on a cold PCM (T PCM = -25°C) Becker containing adipic acid PCM Copper shield Plate 22

23. Enthalpy of sublimation of adipic acid in vacuum (2) Deposition rates of adipic acid at different temperatures have been measured. Enthalpy of sublimation has been inferred by Van’t Hoff relation:  H : enthaply of sublimation T 1 and T 2 : adipic acid temperatures R 1 and R 2 : deposition rates at temperatures T 1 and T 2 R : gas constant 23/10/2015EPSC 2012, Madrid23 We found  H = 131 kJ/mol, in agreement with the literature value (129.3±2.5) kJ/mol

24. Outline i.Introduction to Thermogravimetry ii.Planetary applications iii.The VISTA project iv.Laboratory measurements v.Conclusions 23/10/2015EPSC 2012, Madrid24

25. Conclusions Thermogravimetry can find application in many planetary environments An instrument based on TGA (i.e. VISTA) is under study and development for space applications: it is very light, small and low-power consuming A VISTA laboratory breadboard has been tested by performing measurements of water desorption and enthalpy of sublimation 23/10/2015EPSC 2012, Madrid25