Emerging concepts of Mars Habitability from the Orbital Perspective

Transcription

1 Emerging concepts of Mars Habitability from the Orbital Perspective Outline Introduction First billion years VNIR imaging spectroscopy: the view from MRO/CRISM Evidence for multiple distinctive aqueous environments on early Mars Subsurface hydrothermal Surface weathering and fluvial Future directions & big questions Jack Mustard Brown University COEL Meeting June 8, 2011 Scarp wall showing interesting melange and brecia of altered and unaltered rock, HiRISE Image

2 <<1% of rock record ~50% of rock record KEY QUESTIONS: When was liquid water first stable? When did Earth become habitable/inhabited? What was the nature of the first habitat(s)? (1) Nyquist et al., 2001 (2) Borg et al., 1999 (3) e.g. Valley et al., 2005 (4) Schopf, 2006 (5) e.g. Farquhar et al., 2000

3 GLOBAL GEOLOGIC TIMELINE A mineralogic history of Mars Bibring et al. (2006) Hypothesis: Phyllosilicates and sulfates result sequentially from changes in the surface weathering environment, i.e. early Mars had a thicker atmosphere, was more habitable, some global change occurred Gyr

4 What was the nature of the phyllosilicate formation environment: weathering/pedogenesis, precipitation from standing waters, hydrothermal? (1) Nyquist et al., 2001 (2) Borg et al., 1999 (3) e.g. Valley et al., 2005 (4) Schopf, 2006 (5) e.g. Farquhar et al., 2000

5 CRISM key finding #1: Phyllosilicates more extensive than previously known Mawrth Vallis Nili Fossae Valles Marineris Terra Tyrrhena Terra Sirenum Locations with phyllosilicate Locations with carbonate

6 CRISM key finding #2: Diversity of hydrated/altered mineral phases Phyllosilicates Other hydrated silicates Carbonates Sulfates Fe/Mg smectite Montmorillonite Kaolinite Chlorite Serpentine Al, K mica (muscovite or illite) Prehnite Zeolite (analcime) Opaline silica Hydrated basaltic glass Mg carbonate Fe, Mg mono- and poly- hydrated sulfates Gypsum Jarosite Alunite FeSO 4 (OH) Hematite white=new since 2006 Fe oxides Mustard et al., Nature, 2008; Bishop et al., Science, 2008; Milliken et al., Geology 2008; Ehlmann et al., Science, 2008; Ehlmann et al., J. Geophys R., in press; Murchie et al., J. Geophys. Res., 2009;. Swayze et al., in prep.]

7 Adapted from Murchie et al., JGR, 2009 with mineralogic epochs from Bibring et al., 2006 phyllosian theiikian siderikian clays sulfates anhydrous ferric oxides Deep phyllosilicates Carbonate deposits Layered phyllosilicates Phyllosilicate in fans Plains sediments? Intracrater claysulfates? Meridiani layered Proposed Chemical Environments Valles layered? Siliceous layered?? Gypsum plains? Noachian Hesperian Geologic Eras Amazonian

8 Adapted from Murchie et al., 2009 with mineralogic epochs from Bibring et al., 2006 Alkaline Acidic phyllosian theiikian siderikian clays sulfates anhydrous ferric oxides Deep phyllosilicates Carbonate deposits Layered phyllosilicates Phyllosilicate in fans Plains sediments? Intracrater claysulfates? Proposed Chemical Environments subsurface surface Meridiani layered Valles layered? Siliceous layered?? Gypsum plains? Noachian Hesperian Geologic Eras Amazonian

9 I. Deep phyllosilicates : evidence for a hydrothermal past Excavated by thousands of southern highlands impact craters Exposed in Nili Fossae, Valles Marineris scarps

10 Pre-impact excavated or post-impact generated? extent of impact-induced hydrothermal alteration Central peak Rim D ~ 50km Abramov & Kring, 2005 Working assumption: When phyllosilicates are mapped in ejecta, at least some phyllosilicates in and around the crater are excavated (predate impact)

11 Ehlmann, et al., ICC Mineralogy of S. Highlands Impact Craters Isidis Basin Hellas Basin 1500 km Fe/Mg smectite Mapping of mineral detections from Fraeman et al., Lunar Planetary Science Conf Ehlmann et al., J.Geophys. Res., 2009

12 Selected craters with mineralogy indicating low-grade metamorphism/hydrothermal activity Chlorite/prehnite, illite crater Analcime, opaline silica, Fe/Mg smectite, chlorite Chlorite/prehnite, Fe/Mg smectite/ opaline silica craters 50 km

13 Selected craters with mineralogy indicating low-grade metamorphism/hydrothermal activity Chlorite/Prehnite Chlorite/prehnite, illite crater Analcime, opaline silica, Fe/Mg smectite, chlorite Chlorite/prehnite, Fe/Mg smectite/opaline silica craters Ehlmann et al., JGR, km

14 Ehlmann, et al., ICC Prehnite (Ca 2 (Al,Fe 3+ ) 4 (Si,Al) 8 (OH) 2 ) hydrothermal indicator Formation at T: ºC, P: <3 kbar, X CO2 < P-T stability: prehnite and pumpellyite prehnite 1.5 kbar 400 Prh+Chl+Qtz Prehnite stability Temperature (ºC) Ep+Act+H 2 O (Ep) (Pmp) (Act) Prh+Pmp+Chl (Frey and Robinson, 1999) X CO2

15 Selected craters with mineralogy indicating low-grade metamorphism/hydrothermal activity Chlorite/prehnite, illite crater Analcime, opaline silica, Fe/Mg smectite, chlorite Chlorite/prehnite, Fe/Mg smectite/ opaline silica craters

16 Ehlmann, et al., JGR, in press Analcime/silica/chlorite/smectite assesmblage CRISM spectra Band depth map R: 1.9, G: 2.3, B: 2.2 USGS lab spectra chlorite Mg smectite opal 2.5 analcime

17 Analcime-Silica-Smectite Assemblage HT activity Key mineral is analcime (NaAlSi H 2 0, zeolite) forms in highly alkaline lakes, weathering of glass In hydrothermal systems accompanied by opaline silica, other zeolites, clays, e.g. Iceland or sea water weathering of basalt (e.g. Cann, 1979) Zeolites in hydrothermal systems, Iceland (Weisenberger & Selbekk, 2008)

18 Summary: evidence for hydrothermalism/low T Metamorphism Analcime, Illite/Chlorite, Prehnite CRISM mineral geothermometers for temperatures of alteration Analcime: ºC K mica (e.g. illite): >50ºC Prehnite: ºC, <3 kbar Key question: pre- or post- impact? Requires integrating kinetics of mineral formation and destruction (lab, modeling) hydrocode modeling thermal evolution of impact sites continued remote sensing of Mars Ehlmann, et al., ICC 09-18

19 I. Deep phyllosilicates : evidence for a hydrothermal and impact processes Excavated by thousands of southern highlands impact craters Exposed in Nili Fossae, Valles Marineris scarps

20 (~3.96Ga) Ehlmann et al., JGR, in press OMEGA mapping - Pyroxene (LCP, HCP by P. Thollot), olivine (Poulet et al., 2007)

21 50 km

22 The Noachian basement altered (to Fe/Mg smectite) breccia blocks (altered/unaltered) are common throughout raised ridges upon erosion: conduits of fluid flow? Low-Ca Pyroxene Fe/Mg smectites Fe-Phyllosilicate Mustard et al., 2009, JGR mafic (low-ca pyx) materials cap Q: do impacts create or simply redistribute clays? Fe/Mg smectite Low-Ca pyroxene 25 m 25 m 5 km PSP_002176_2075 PSP_006023_ m 22

23 Fe/Mg smectite basement mineralogy Dominantly Fe/Mg smectite Variable dominant cation Dioctahedral nontronite Trioctahedral saponite And probably everything in between Variable hydration state Variable Fe 2+ Additional hidden components? How much Fe/Mg smecitite? (on-going lab work to test Shkuratov and Hapke radiative transfer models with alteration mineral+mafic mineral mixtures) Mg-OH 1.41 Al-OH, H 2 O 1.43 Fe-OH Band position guide 1.9 variable amt. H 2 O 2.28 Fe-OH 2.32 Mg-OH Ehlmann et al., JGR 2010

24 Nature of Deep phyllosilicates >100s m thick, not bedded Evidence for effects of hydrothermalism Morphology: Ridges when eroded fluidized fractures? Mineralogy: indicator minerals such as prehnite, analcime Related to impact (early bombardment0 Brecciated Including layered (sedimentary?) breccia blocks Extensively altered Phyllosilicates in the matrix and blocks

25 II. Second generation aqueous activity -Layered phyllosilicates -Carbonate deposits -Fluvial/lacustrine systems

26 What is the record of near surface alteration? Above the Fe/Mg smectite basement in Nili Fossae, geomorphic/mineralogic units with different alteration minerals Ehlmann et al., JGR, 2010

27 FRT0000A053 Ehlmann et al., JGR, km

28 stratigraphy cap kaolinite Fe/Mg smectite kaolinitebearing Spectrally indistinct cap Fe/Mg smecitebearing 1km

29 What is the record of near surface alteration? Above the Fe/Mg smectite basement in Nili Fossae, geomorphic/mineralogic units with different alteration minerals Kaolinite zone of alteration (1) basalt (partially) Fe/Mg smectite (2) Enhanced leaching loss of loss of Ca2+, Mg2+, Fe2+ ions kaolin group mineral Al 2 Si 2 O 5 (OH) 4 (Analog: soil formation under intermittantly wet conditions) Carbonate zone of alteration Weathering of ultramafic rocks Mg in olivine Mg carbonate (Analog: serpentinites in Oman, N. California) Ehlmann et al., JGR, 2010

30 Carbonate/Serpentine/Olivine co-occurrence: hypotheses Sources of economic magnesite on Earth (Möller, 1989) Hydrothermal fluids Serpentinization SUBSURFACE Diagenesis of marine beds Weathering of olivine and serpentine rich bodies Precipitate in playas fed by ultramafic catchments SURFACE Ehlmann et al., LPSC 09; GRL in prep McLaughlin, CA (April 2009) Serpentine and carbonate from Oman ophiolite (Keleman and Mater, 2008)

31 II. Second generation aqueous activity -Layered phyllosilicates -Carbonate deposits -Fluvial/lacustrine systems

32 Fluvial acitivty post-dates deep phyllosilicates and layered phyllos./carbonates fluvial activity?? Mangold et al., 2007

33 Jezero Volcanic Crater delta deposits Olivine-rich -Closed basin with defined inlets and an outlet Carbonate/clay -Mineralogy of the catchment basin: Fe/Mg smectite and Mg carbonate 75 E 80 E A phyllosilicate µm depth B elevation (m) m C Isidis Basin Ehlmann et al., Nature Geosci., 2008 Ehlmann et al., Nat. Geosci., 2008

34 Hydrothermal Alteration: Spring and/or Fumerole deposit in Hesperian Mars Well Exposed Volcanic deposit Possibly the most recent near-surface habitable environment

35 Syrtis Major Volcanic Complex Nili Fossae Syrtis Major Isidis Basin Nili Patera

36 Nili Patera Caldera Nili Fossae Syrtis Major Isidis Basin Nili Patera

37 CTX Image 6 m/pixel Dacite (silica-rich volcanic THEMIS Multispectral

38 Hydrated Silicate (e.g. Siliceous Sinter, opaline silica)

39 Nili Patera Volcanic Cone

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42 Geologic Context of Nili Patera Hydrothermal System Model Complex Syrtis Major caldera indicated several eruptive episodes. Hiesinger and Head 2004 Dacite bearing flow in Nili Patera would require magmatic differentiation and a long lived system. Christensen et al Silica is deposited on the flank of the cone, in nearby mounds and in a field of deposits on the dacitic flows. Pirajno and Kranendonk 2005

43 Adapted from Murchie et al., 2009 with mineralogic epochs from Bibring et al., 2006 phyllosian theiikian siderikian clays sulfates anhydrous ferric oxides Deep phyllosilicates Carbonate deposits Layered phyllosilicates Phyllosilicate in fans Plains sediments? Intracrater claysulfates? Meridiani layered Proposed Chemical Environments Thick altered basement, hydrothermal activity and impact churning important processes Thinner alteration layer; surface weathering processes and precursor mineralogy are the important controls Valles layered? Siliceous layered?? Gypsum plains? Noachian Hesperian Geologic Eras Amazonian

44 Optimum Habitable Environments, that are Recognizable from Orbit, have Evolved

45 Summary and Questions for the future On ancient Mars: think locally, not globally Key advance of this generation of VNIR imaging spectrometers: contextualization of mineralogy with morphology at high resolution multiple aqueous environments on early Mars, varying with space and time Typical Early-Middle Noachian Mars is alkaline and hydrothermal in character The action (and habitats) were deep in the crust need for analog studies what is the role of impacts? How do surface weathering/bodies of water fit in? Later (and brief?) in time, highly variable in mineralogy How common are clays and what minerals accompany them? Implications for water budget, further refinement of environmental setting Do deep phyllosilicates preserve the first potential habitat for life on Mars (and Earth)?