Broad Perspectives on Preferred Types of Mars Science Laboratory Landing Sites: Experience from Characteristics of Previous Landing Sites and Developing Sedimentologic Facies Models M. Golombek and J. Grotzinger Jet Propulsion Laboratory and Caltech

Golombek & Grotzinger’s Guide to MSL Landing Sites Layered Sedimentary Rocks –Extensive Section Outcrop, No Float –Not Hesperian or More Cratered Surface No/Little Dust –Dark, Low Albedo Low Energy Depositional Sedimentary Facies –Clay rich mudstones distal fluvio-deltaic or lacustrine –Bottom-growth evaporites - sulfates

MSL Science Objectives Focus on Habitable Environment PP Requirements Focus on Ancient Habitable Environments Layered Sedimentary Rocks –Well Suited to Address Ancient Environments Meridiani Planum Sulfates –Top of Section of Layered Sedimentary Rocks –Formed in Late Noachian –Approximately Coeval w/Geomorphic Indicators Valley Networks, Eroded Terrain, Layered Rocks –Formed in Wet, Likely Warm Environment

VL1 MPF Meridiani VL2 Gusev Landing Sites on Mars 5 “Ground Truth” Samples 15°N 15°S Meridiani Eroded Highlands

Meridiani Planum Site Smooth Plains Overly Noachian Cratered Terrain Generally Bury Valley Networks flow to NW, Down Topographic Slope Created by Tharsis Loading Population Old Degraded Craters >1 km Diameter are Noachian Lightly Cratered Indicates Young Surface Age

Bright Unit Mapped As Package of LN Sedimentary Rocks Surface Age Late Amazonian Hesperian Craters Gone Erosion of m of Material Meridiani Hynek, 2004

Meridiani Planum Late Noachian Denudation Hynek and Phillips [2001] ~1 km Erosion in LN [Just before Evaporites Deposited] Argued for Precipitation & Runoff Warm and Wet Environment

Meridiani Planum Late Noachian Sulfates “Dirty Evaporites” Liquid Water Stable Wet and Likely Warm Environment

Dells MI Mosaic Dirty Evaporites Document Early Wet & Likely Warm Environment

Overgaard

Lower unit Middle unit Upper unit Burns Formation

Network of Interdune Depressions

Interdune Depression

100 km

MSL to Layered Sedimentary Rocks Likely Formed in Wet and Warm Conditions and Record Aqueous Environment OMEGA Identified Sulfates in Many Such Terrains Substantial Stratigraphic Section Accessible [Meridiani ~10 m]

No Float! Outcrops Only Instructions on Door of JPL , 1998 to present Occupant: T. Parker

No Float/Outcrop Gusev Hesperian Cratered Plains Gusev Random Sample Hesperian Cratered Plains Variable Thickness Impact Generated Regolith Likely Formed as Lava Flows No Outcrop Found Cratered Plains

Cratered Plains Angular Basalt Fragments Likely Basalt Flows Impact Generated Regolith

Bonnevill e Fresh Crater, Fresh Ejecta, Little evidence for Backwasting No Debris Chutes or Talus, Jumbled Regolith of Basalt Ejecta ~10 m Thick No Outcrop

Viking Lander 1 Late Hesperian Cratered Surface Limited Low Outcrop Lot of Rock Float

No Outcrop Rocks are Float Viking Lander 2

Lightly Cratered Surface for Intact Stratigraphy Cratered Surface: Beware of Float, Regolith and No/Little Outcrop

No Dust, Dark Low-Albedo Site Meridiani - First Landing Site in Dark Region, Albedo Low ~0.1 Basalt Sand, Hematite Granule Lag Surface Ripples No/Little Dust to Mask Remote Sensing; More Effective Surface Operations to ID Rocks & Soils to Investigate Further

Sedimentary Facies Low Energy Environments –Maximize Accumulation & Preservation of Biomarkers –Burns Formation at Meridiani Most High Energy Sand Dune and Sand Sheet Not Optimal for Accumulation or Preservation Two Optimal Facies –Clay Rich Mudstones: Deposited in Distal Fluvio- deltaic or Lacustrine Setting –Bottom Growth Evaporites –Examples of Each & How to Recognize Ideal Landing Site Has Both Facies

Eolian Dune Sand Sheet Interdune

Sulfate (Gypsum) Evaporites in Playa Lake

Microbial Mats Being Entombed, Could Protect from Degradation (Salts Impermeable) Chemical sediments have high potential to preserve organic compounds

Microbial Mat Textures Preserved in Evaporites

Example of Layered Sulfates Headwaters of Maja Valles Floor Around -2 km Elevation 4.5°S, 297.5°E Juventae Chasma

4S 297E 5S 296.5E

Juventae Chasma Layered Deposits Gypsum (Ca Sulfate) Kieserite Mg Sulfate) Stratigraphic Transition - Minerals with Different Solubilities Bibring et al. 2005

Land and Traverse on Sand Sheet Sample Stratigraphic Column

200 m On Earth, organic material preferentially sequestered by clay minerals Preservation organics enhanced by phyllosilicate surfaces Search Strategy - Look for phyllosilicates in spectral imaging and Stratal Geometries to Identify Distal Environments - Clays and Organics Example Distal Clay Rich Site Clinoforms

Channel Clinoforms Prograding Delta

Prograding Clinoforms Condensed Section, Decrease in Grain Size, Distal Clay Rich Enhanced Organic Accumulation and Preservation

Prograding Clinoforms Yellow Lines Define Single Depositional Sequence Convergence of Clinoforms - Section Condensation Decrease in Grain Size Accumulation of Clay Minerals and Organics

Depositional Sequences Conformable succession of genetically-related strata, bounded at the top and base by: –Unconformities (surfaces of erosion) or their –Correlative conformities (surfaces lacking erosion)

Sequence Stratigraphy Seismic Reflection Data - Prograding Clinoforms Sequence Boundaries - Stratal Truncations and Onlap Define Cinoforma Interpretation of Facies - Brown Shales, Downdip of Sands

Permian Clinoforms in Last Chance Canyon

Golombek & Grotzinger’s Guide to MSL Landing Sites Layered Sedimentary Rocks –Extensive Section, Intact Stratigraphy, Known Geologic Setting - Related to Geology of Mars Outcrop, No Float, Lightly Cratered –Not Hesperian or More Cratered Surface No/Little Dust, Effective Surface Remote Sensing –Dark, Low Albedo Low Energy Depositional Sedimentary Facies –Clay rich mudstones distal fluvio-deltaic or lacustrine setting, Look for clays and clinoforms –Bottom-growth evaporites - sulfates, extensive stratigraphic section, better chance to find bottom growth