Remote Detection of B i o S i g n a t u r e s

1. Remote Detection ofB i o S i g n a t u r e s A d r i a n B r o w n

2. Who am I – why am I here? • First Year PhD student at Australian Centre for Astrobiology, Macquarie University • Supervisors Prof Malcolm Walter (Director of ACA), Dr. Thomas Cudahy (CSIRO) • Background of Engineering and Software Engineering, now traveling on the Astrobiology wheel along the ‘Geology’ spoke

3. Overview • Introduction • Definitions – My Dictionary • Three Year Plan • Mineral Mapping of the North Pole Dome • Backgrounder: Development of the North Pole Dome • Backgrounder: Hyperspectral mapping and HyMap • What do I hope to achieve? • Spatial Geochemical Modeling of a Hydrothermal Vein • Backgrounder: Hydrothermal alteration • What do I hope to achieve? • Martian Simulation • What do I hope to achieve? • Conclusion – questions?

4. Definitions • Remote sensing – detection of physical characteristics of solid surfaces at distances over 2km • Hyperspectral – high spectral resolution data sets (ie. HyMap 126 spectral bands) as opposed to multispectral (LANDSAT 7 bands) data sets. • Hydrothermal zone – water at elevated temperatures in disequilibrium with the rock through which it travels • Stromatolites – microlaminated sedimentary structure ?created by the secretions of cyanobacteria in algal mats or benthic bacteria around hydrothermal vents

5. Three Year Plan • Research covers remote sensing and interpretation of mineral maps, geochemical modeling and Martian geology

6. Year 1 – Mineral Mapping of the North Pole Dome (or, let’s find a weird Earth analogue)

7. North Pole Dome • Setting – eastern Pilbara, north Western Australia • Situated north of Hamersley Ranges (BIFs) • Warrawoona Group - early Archaean (3.2-3.5 Gya) • ‘North Pole’ Dome ironically named North Pole Dome Shark Bay

8. North Pole Dome • Doming due to periodic mantle events (Van Kranendonk 2000) • Very contentious – my main sources are Van Kranendonk 2000, Nijman, 1998, Buick et al 1995, Barley 1993. • Hydrothermal and volcanic activity spans less than 85 million years, doming started during same time interval.

9. Development of North Pole Dome North Pole Monzogranite • Exposed over 6km2 at core of North Pole Dome • Synvolcanic laccolith – medium to coarse grained biotite monzogranite • Dated at 3459 Ma, same age as the volcanic Panorama Formation

10. Development of North Pole Dome Mount Ada Basalt • Massive thoelitic basalt with pillow basalt occurences • Lower contact is intrusive - North Pole monzogranite • Setting is sub-aqueous • Cherts absent except where transected by boxwork of chert-barite dykes, however these are post-depostional

11. Development of North Pole Dome Dresser Formation • Contains the worlds oldest stromatolites and microfossils • Buick interpreted the environment as coastal (Barley 1993) • Nijman hypothesized hydrothermal origin, deep marine environment (Van Kranendonk 2000) • Perhaps a combination of the two is possible? (note small smokers on Buick photo) Buick Nijman/Van Kranendonk

12. Development of the North Pole Dome Duffer Formation • 3466 Mya • Dacitic tuff, agglomerate and lava flows • Only thin thickness (100m) but an important horizon marker around the Dome

13. Development of the North Pole Dome Apex Basalt and Panorama Formation • Basalt and Felsic volcaniclastics respectively • ‘Panorama volcano’ located just NW of NPD • 3458 Mya for Panorama

14. Development of the North Pole Dome Strelley Pool Chert • Silicifed carbonate forms chert veins, in some parts incompletely altered • Stromatolitic horizons up to 8m thick, including ‘Trendall locality’ • Formed during a hiatus in volcanism but with continuing hydrothermal activity • Conformably overlain by the sub-aqueously deposited Euro Basalt, dated at 3434 Mya.

15. Why the North Pole Dome? • Why choose North Pole? • We have stromatolites and microfossils • Little to no metamorphism due to never being deeply buried • We have an excellent dataset with low vegetation • Is it actually like Mars? • Similar age but different weathering processes • Sulfate deposits on Mars and NPD, but barite? • Low vegetation but not *no* vegetation • Dust not as prevalent • Vertical tectonics? • Weathering beneath a oxygen and water laden atmosphere

16. Hyperspectral Mapping • Basic Principles of Passive Remote Sensing Your House A tree Rock

17. Hyperspectral Mapping • Absorption bands caused by photons being absorbed at specific wavelengths • Large number of frequencies covered means we can discriminate between individual minerals • We can discriminate using band ratios (basic) or continuum removal (more complex) or principal components analysis inspired methods (more complex again)

18. Vibrational Processes for H2O • u3 – asymmetric stretch (fundamental 2.903 mm) • u1 – symmetric stretch (fundamental 3.106 mm) • u2 – H-O-H bend stretch (fundamental 6.08 mm)

19. What is this SWIR thing? • SWIR = Short Wave Infra Red (2.0-2.4 micrometers) • No water absorption lines • In IR, photon interactions are due to vibrational processes • Strong hydroxl overtone (2 uOH ) OH stretch absorption line • Modified according to the ion the OH molecule is attached to Mg or Al • Makes it possible to determine alteration minerals on the ground

20. Hyperspectral Complications • Spatial and spectral crossover (calibration) • Atmospheric correction • Sun’s energy output described by Planck’s function • Unmixing– when two or more minerals occupy a pixel • These are all surmountable to some degree! Mineral A Mineral B pixel width (5m)

21. What do we hope to achieve? • Produce mineral maps showing occurrences of OH altered minerals around the Dome • Spatially relate occurrences of stromatolites and microfossiliferous horizons

22. How are stromatolites and microfossils related to minerals? • Stromatolites may occur in shallow water around hydrothermal vents (though not cyanobacteria) • Microfossils may occur in kerogenous hydrothermal veins of black and white chert

23. Year 2 – Modeling the Hydrothermal Vein (or – how on Earth did that get there?)

24. Hydrothermal Alteration • Mineralogy of hydrothermally altered rocks depends on prevailing physical conditions at time of alteration • Chemistry of fluid phase • pH • Salinity • Fugacities of oxygen and sulfur • Composition of original host rocks • Temperature of host rocks and fluids • Ideally alteration varies vertically and horizontally , most intense closest to source • Often controlled by veins, fractures and faults

25. Relevant Previous Research • Lovell and Guilbert researched alteration zoning of Cu porphyries in Nevada • Helgeson modeled geochemistry of alteration minerals • Griffith and Shock and EQ3/6 researched geochemical alteration pathways in Martian meteorites

26. What can we hope to achieve? • Can we state something about the conditions under which the system formed, eg. Was a brine (perhaps seawater) involved? • Can we get an idea of the temperature and pressure conditions in various parts of the Dome? Vapour phase? Acid-sulfate vs. Neutral chloride? • Can we work out where the barite came from? (hard) • Is the spatial resolution of our data set good enough to discriminate alteration zones (typically 50m wide) ?

27. Year 3 – Martian Simulation (or, what on Earth will Mars look like?)

28. Relevant Research • Newsom, Gulick, Griffith and Shock, Harrison and Grimm have studied Martian hydrothermal systems, including impact related melt sheets • Viking IR, Phobos ISM, but large pixel size • TES, THEMIS operate in mid IR • OMEGA - 500m pixel size (2004) and CRISM - 13m pixel size (2008)

29. What can we hope to achieve? • Can we translate dust seen in TES/THEMIS to the VNIR/SWIR? • Use characteristics of North Pole Dome to simulate a hydrothermal system on Mars • But which characteristics are reasonable? Size of intrusion, country rock, temperature, what about barite? • Following simulation, we can predict what we might see with CRISM on MRO • Can we map hydrothermal systems and alteration zones with CRISM and then point out the hotspots for stromatolites or microfossiliferrous horizons?

30. Stargazing (thrown in for free) • Ore deposits on Mars – for the future colonist – look for lineaments and alteration zones • Ore deposits on asteroids or planetary satellites?

31. Conclusion

32. References • Barley, M.E., 1993. Volcanic, sedimentary and tectonostratigraphic environments of the ~3.46 Ga Warrawoona Megasequence: a review. Precambrian Research 60 p. 47-67. • Buick, R., Thornett, J.R., McNaughton, N.J., Smith, J.B., Barley, M.E. and Savage, M., 1995. Record of emergent continental crust ~3.5 billion years ago in the Pilbara Craton of Australia, Nature, 375, p. 574-577. • Griffith, L.L., and Shock, E.L., 1997. Hydrothermal hydration of martian crust: Illustration via geochemical model calculations. Journal of Geophysical Research 102, p. 9135-9143. • Gulick V.C., 1998. Magmatic intrusions and a hydrothermal origin for fluvial valleys on Mars. Journal of Geophysical Research 103, no. E8, p. 19365-19387. • Harrison K.P. and Grimm, R.E., 1999. A conservative approach to Hydrothermal Systems on Mars, LPSC XXX Proceedings, p. 1941. • Lowell and Gilbert, 1970. Lateral and Vertical Alteration-Mineralization Zoning in Porphyry Ore Deposits, Economic Geology65, p. 373-408 • Newsom, H.E., 1980. Hydrothermal alteration of impact crater melt sheets with implications for Mars, Icarus, 44, p. 207-216 • Nijman, W., de Bruijne, K.C.H. and Valkering, M.E., 1998. Growth fault control of Early Archaean cherts, barite mounds and chert barite veins, North Pole Dome, eastern Pilbara, Western Australia. Precambrian Research 88, p. 25-52. • Van Kranendonk, M.J., 2000. Geology of the North Shaw 1:100 000 Sheet Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 86p. Department of Minerals and Energy, Western Australia.

33. Picture/Movie Acknowledgements • MER website, http://athena.cornell.edu/the_mission/rov_video.html • Introduction to Hyperspectral Analysis by Peg Shippert, www.rsi.com • Black Smoker Webquest, http://www3.district125.k12.il.us/faculty/bfisher/blacksmokerlinks.html

34. Questions (or, what was all that about?)