1. Julian Chela-Flores Julian Chela-Flores The Abdus Salam ICTP, Trieste, Italia and Instituto de Estudios Avanzados, Caracas, Instituto de Estudios Avanzados, Caracas, Republica Bolivariana de Venezuela The Origins: how, when and where it all started, Accademia Nazionale dei Lincei. Centro Linceo Interdisciplinare “Beniamino Segre”, Roma, 22 May 2006 Evolution of the universe: From Astrophysics to Astrobiology Distinguishing between signatures of past life and nonlife Exploring the Solar System - Missions and Techniques EGU 2008, Austria Center Vienna, Lecture Room 11; 15 April 2008: 9.15

2. Authors Julian Chela-Flores The Abdus Salam ICTP, Trieste, Italia and Instituto de Estudios Avanzados, Caracas, Republica Bolivariana de Venezuela Narendra Kumar Indian Institute of Science, Bangalore, India Joseph Seckbach The Hebrew University of Jerusalem Israel Vinod Tewari Wadia Institute of Himalayan Geology Dehradun, India.

3. Future missions to Europa Future missions to Europa  There is a possibility for returning to Europa with both the LAPLACE mission,  The outline of LAPLACE has been summarised by Blanc, M. and the LAPLACE consortium (2008). and the Europa Geophysical Explorer. Europa Geophysical Explorer

4. Habitability  For NASA's Science Mission Directorate habitability is also the focus of its Solar System Exploration Roadmap.  “Is Europa habitable?” plays a prominent role in ESA’s Cosmic Vision Plan for 2015-2025 that has been adopted for the LAPLACE mission. The other two Goals are related with habitability:  What have been the conditions for the formation of the Jupiter system? How do they contribute to the possible emergence of life?  How does the Jupiter system work? How does the system contribute to the conditions for habitability?

5. Plan of the talk  The patchy surface of Europa: A major challenge in the exploration of Europa. A major challenge in the exploration of Europa.  Chemical elements on the surface of Antarctica and Europa.  Biogeochemistry.  A ‘fluctuation test’ for the exploration of Europa.  Instrumentation.  Discussion.

6. The patchy surface of Europa: A major challenge in the exploration of Europa International Journal of Astrobiology (2006), 5, pp. 17-22 (Cambridge University Press). Part I

7. Ice-covered oceans over a silicate core: The cases of Europa and Titan

8. A hydrobot  Galileo revealed evidence for an internal ocean, Horvath et al, 1997 but we argue that for determining the habitability of Europa, waiting to enter the ocean by 2028 may be unnecessary. Endurance, 2008

9. Possible sources of the stains  External source: Ions may be implanted from the Jovian plasma. Ions may be implanted from the Jovian plasma.  Internal source: Sulfur may be due to cryovolcanism. Sulfur may be due to cryovolcanism.  Could the source be biogenic? We discuss the use of mass spectrometry We discuss the use of mass spectrometry in the context of the available instrumentation.

10. Chemical elements on the surface of Antarctica and Europa Part II

11. Antarctica’s subglacial lakes

12. Antarctica’s Dry Valleys:  Beacon  Taylor  Victoria  Wright

13. The Taylor (Dry) Valley Lake Hoare (9) Lake Bonney (7)

14. A cross-section of the icy surface of Lake Hoare Algal mat pieces on the surface of Lake Hoare (Parker et al, Phycologia, 1982)

15. Annual escape of sulfur (kg) by the loss of algal mats

16. The Europa icy surface (Spectrometer data from near IR) and ‘patchy’ albedo per pixel High resolution albedo image albedo image Distribution of non-ice component 4 km/pixel McCord et al, Science 280 (1998), 1242

17. Where should we land?

18. Part III Biogeochemistry

19. The delta 34 S-parameter  The meteorite coincides with the standard (st) terrestrial ratio of the isotopes 32 S and 34 S. For a given sample (sa), we define with respect to this meteorite:  The Canyon Diablo Meteorite (CDM) is a troilite (FeS), that was found in Arizona:

20. Sulfate-reducing bacteria

21. 4H 2 + H 2 SO 4 –» H 2 S + 4H 2 O + 39 kilocalories 4H 2 + H 2 SO 4 –» H 2 S + 4H 2 O + 39 kilocalories  The H 2 S then combines with Fe in sediments to form grains of the biogenic mineral pyrite. Iron sulfide, FeS 2  Unite H with S atoms from dissolved sulfate ( SO 4 -2 ) of seawater to form hydrogen sulfide H 2 S : of seawater to form hydrogen sulfide H 2 S :

22. The sulfur isotopes are divided between biogenic minerals and sulfate minerals  Dissolved sulfate on evaporation forms sulfate minerals depleted of 32 S by 20 per mil.  The H 2 S given off by the bacteria is enriched in 32 S by 20 per mil.

23. Sulfur ions on Earth, meteorites and the Moon Terrestrial Meteoritic Lunar -40 From measurements in basins off California: insoluble sulfide, mostly pyrite. Sulfate coexisting with seawater The delta 34 S-parameter

24. Part IV A ‘fluctuation test’ for the exploration of Europa

25. The fluctuation test (Luria and Delbruck)   Luria first assumed that mutations in a growing bacterial culture could be acquired as a result of its exposure to virus (phage).  very small fluctuations  The observed number would then have very small fluctuations (slight deviations from the mean).   If this was the case, the number of resistant individuals would vary very little from one experiment to the next.

26. Can bacterial fluctuations be large?  Alternatively, Luria also assumed that a mutation can occur before the bacterium was confronted with phage.  The number of resistant bacteria would depend on the time elapsed since the mutation. The number of resistant individuals shows exponentially large fluctuations.  The observed bacterial exponential growth suggests to detect such deviations from Gaussianity with higher order statistics.

27. Instrumentation Part V

28. Difficulties with the the dust analyzers  32 S is isobaric (same m/z) with 16 O 2. There would not have sufficient resolution with the current design to identify the contributions from S and its interference with the O 2 at m/z 32 and 34.  The instrument required needs to count about 1x10 6 sulfur ions to get a precision of +/- 5 per mil on the delta 34 S- parameter. So the likely ion counts is a key issue.

29. The cloud generated around Europa  We expect it to mirror the large S-isotope deviations on the surface.  Consequently, dust detectors in orbit should record similar non-Gaussian distributions as conjectured for the surface itself, with non-vanishing cumulants of order greater than 2.  On the other hand, the contributions from the O 2 atmosphere should be described instead by a Gaussian distribution with vanishing cumulants of order greater than 2.

30. A possible instrument is a penetrator  A UK Consortium has already argued in favour of landing with penetrators on the icy surface of Europa.  Penetrators are considered in the recent paper of Blanc, M. and the LAPLACE consortium summarising the mission.  In this case, if the Europan surface is to be probed with penetrators, MS would be a valuable alternative for understanding the icy patches.

31. The mass constraints for MS on penetrators are severe 120 x 60 mm; 500 g  To illustrate that miniaturization is not the main challenge, we point out suitable instrumentation: The current MS on Cassini (Ion and neutral MS), and The current MS on Cassini (Ion and neutral MS), and The work on miniaturised MS by Peter Wurz and co- workers at the University of Bern. The work on miniaturised MS by Peter Wurz and co- workers at the University of Bern.

32. Discussion  The use of MS is suggested for a dust analyzer and, if landers are possible, MS is also suggested for penetrators.  The work of miniaturization of the instrumentation does not seem to be the greatest challenge in interpreting S- isotopes either in orbit or on the icy surface of Europa.

33. pdf files can be downloaded from: http://www.ictp.it/~chelaf/ss16a.html