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

Remote Detection of
BioSignatures
Adrian Brown
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
Overview
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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?
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
Three Year Plan
• Research covers remote sensing and
interpretation of mineral maps, geochemical
modeling and Martian geology
Year 1 – Mineral Mapping
of the North Pole Dome
(or, let’s find a weird Earth analogue)
North Pole Dome
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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
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.
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
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 chertbarite dykes, however these are
post-depostional
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
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
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
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.
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
Hyperspectral Mapping
• Basic Principles of Passive Remote Sensing
Rock
Your House
A tree
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)
Vibrational Processes for H2O
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u1 – symmetric stretch
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(fundamental 3.106 mm)
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u2 – H-O-H bend stretch
(fundamental 6.08 mm)
u3 – asymmetric stretch
(fundamental 2.903 mm)
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
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)
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
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
Year 2 – Modeling the
Hydrothermal Vein
(or – how on Earth did that get there?)
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
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
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) ?
Year 3 – Martian Simulation
(or, what on Earth will Mars look like?)
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)
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?
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?
Conclusion
References
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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 Geology 65, 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.
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/blacksmok
erlinks.html
Questions
(or, what was all that about?)