Wet environment reconstruction using IR spectra on Mars

Wet environment reconstruction using IR spectra on Mars Akos Kereszturi Konkoly Astronomical Institute, MTA CSFK Mars Astrobiology Group (ESA RCL) OTKA PD 105970

Background: • aim: use laboratory analysis to reconstruct wet conditions on Mars • this presentation: earlier results + new project idea • results: • Mars surface morphology • past water (Bolyai Fund: 2011 -2012) • project: • Mars surface IR spectroscopy + laboratory analysis • past wet conditions (OTKA Fund: 2012. 09. 01. -) Contenst: • Martian wet locations • paleoenvironment reconstruction • examples from morphology • examples from volumetric and discharge calculations • overview of wet environments • IR spectra to understand wet alteration • available CRISM , THEMIS data • laboratory spectra, FTIR measurements

Introduction: evidences for past water on Mars • channels, shorelines, Gilber-like deltas, cross-bedding features, lake basins… • wet alteration products (Al-clays, hydrated sulfates, zeolites…) • inside Mars meteorites (clays, carbonates) • ice on and below the surface today + paleoclimate indicators water OK, but what was it like? Temperature? p. H? Salinity? …

Surface morphology channel shape erosion style Methods: • imaging data (MOC, THEMIS, HSRC, CTX, Hi. RISE), topography (DTMs) • GIS software, model computations, error level • channel identification: images / databases (some % catalogued) • measurements: cross-sectional, longitudinal profiles, network str. • reason: different erosion (climate related) Kereszturi 2011 Planetary and Space Science

Surface morphology volume, duration delta-like sediment • volume estimation: • eroded (missing) regolith • deposited sediment volume • discharge computation (Modified Manning / Darcy. Weisbach equations) • sediment transport rate • active duration • result: water volumes involved, wet periods (climate related) Example: • Gale crater NW valley • eroded: 0. 34 km 3 • deposited: 0. 23 km 3 • flow speed: 30 -50 km/h • sed. transp. rate: 0. 1 kg/m 3 • active duration: 100 -500 h Kereszturi 2012 Planetary and Space Science fan cross profile

Surface morphology other temporal parameters • relative, absolute ages • crater density calculations • different erosion style at different ages • morphology – age correlation • probably climatic forces older sections younger sections

Summary: compare different wet environment types: • calculations on fluvial activity • estimation on polar liquid interfacial water (today) • other authors: freezing timescales of lakes, weathering durations • results: • separate groups with overlapping zones water ice + • connections with geological evolution thin liquid film • but great uncertainty • should be improved… CRISM spectra Kereszturi 2012 Astrobiology

Possible solution: IR spectroscopy (project 2012 -) • OTKA project started Sept. 2012. • identify wet alteration products • wet conditions mineral alteration spectral identification • best candidates: phyllosilicates, hydrated sulphates • models past temperature, p. H, salininty, water activity, rock/water ratio, duriation • phyllosilicates moderate p. H, high aw • montmorillonite (Columbia Hills) alkaline conditions • kaloinite (many locations) acidic • sulphates acidity low water/rock ratio, short duration • assemblages of hydrated minerals fluvial channel delta-like depositional structure weathered minerals

Possible solution: IR spectroscopy (project 2012 -) • CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) • onboard Mars Reconnaissance Orbiter • multi- / hypespectral • 0. 4 -3. 9 µm • resolution: • 20 m/px 544 wavelengths • 200 m/px 72 wavelengths • THEMIS (Thermal Emission Imaging System) • onboard Mars Odyssey • 9 bands: 6. 8 -14. 9 µm (thermal IR) • 5 bands: 0. 42 -0. 86 µm (visible - near IR) • resolution: • global thermal IR bands 100 m • 60% in visual bands 18 m • influencing factors: • aerosols (dust, vapor) • surface dust cover • particle size fluvial channel delta-like depositional structure weathered minerals

Possible solution: IR spectroscopy (project 2012 -) • mineral identification on Mars using library spectra • own data: • FTIR at Institute for Geological and Geochemical Research • range: 1. 5 -28 µm • spectra of clays, sulphates with known H 2 O content • eample: • dehydrataion of zeolite • 1. 9 µm band disappears, also may shift Extrapolation not easy: • phyllosilicates moderate p. H, high aw • montmorillonite (Columbia Hills) alkaline conditions • kaloinite (many locations) acidic • assemblages of hydrated minerals

First targets laboratory Mars • clay-like smectites (phyllosilicate) • characteristic vibrational absorption near 2. 3 μm and a 1. 9 μm band indicating molecular H 2 O, also at 1. 4 μm • not easy mixed-interlayered, Fe-Mg substitution, diverse particle size… • in lab we can „play” with these factors Used data: • FTIR spectrometer (lab): 1. 25 -28 µm • CRISM data (Mars): 0. 4 -3. 9 µm • THEMIS data (Mars): 0. 4 -15 µm

First location • preliminary example: • Nanedi Valles delta • 2. 1 nm absorption min. monohydrated minerals • elevated clay level? delta lake basin Kereszturi 2007 LPSC