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Assessing Habitability in Gale Crater

Dawn Y. SumnerProfessor of Geology, University of California, Davis

MSL Long Term PLanner

Mastcam 34 image acquired Sol 3 Image Credit: NASA/JPL-Caltech/MSSS

Tuesday, August 21, 2012

A Brief History of Dawn’s Role in Assessing Habitability on Mars

• 2003-2004• Dawn and Andrew Steele led the MEPAG effort to revise the scientific goal to “Determine If Life Ever

Arose on Mars”• Challenge: How do you search for something in a scientifically productive way if what you are looking for might not even exist?

• MEPAG published restructured scientific goals to search for evidence of life on Mars:• A. Assess the past and present habitability of Mars• B. Characterize carbon cycling in its geochemical context• C. Assess whether life is or was present on Mars

• 2004-2010• MSL Mission Goals are Defined and Refined in Response to Abundant Evidence of Water on Mars• Focus: Assessing the Habitability of a Site on Mars

1. Determine the nature and inventory of organic carbon compounds2. Inventory the chemical building blocks of life (carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur)3. Identify features that may represent the effects of biological processes4. Investigate the chemical, isotopic, and mineralogical composition of the martian surface and near-surface geological materials5. Interpret the processes that have formed and modified rocks and soils6. Assess long-timescale (i.e., 4-billion-year) atmospheric evolution processes7. Determine present state, distribution, and cycling of water and carbon dioxide8. Characterize the broad spectrum of surface radiation, including galactic cosmic radiation, solar proton events, and secondary

neutrons

• Dawn Works on Landing Site Selection

• 2011• Gale Crater is Chosen as the Curiosity Landing Site• Dawn Proposes 4 Example Scientific Investigations for the Base of Mt. Sharp (Slides 4-7)• Many Other Great Ideas Proposed by Others

• 2012• We are in Gale Crater!• Dawn is a Long Term Planner for the Mission and Loving It

2


Gale Crater as a Geology Field Area

150 km in diameter; 5 km-high mountain3Image Credit: NASA/JPL-Caltech/MSSS/HRSC


Relationships Among Hematite, Sulfates, and Clay Minerals• Hypothesis: A clay mineral bed is present within the lower mound strata, and some clay minerals are intermixed with sulfates

in overlying strata (Milliken et al., 2010). • Test: Characterize bedding by texture, elemental composition, and mineralogy to see if a clay mineral-rich layer is present and

to characterize the spatial relationships among all hydrous minerals present.• Importance:

• 1. Constrain whether clay mineral accumulation represents a depositional event or a long-term process. • 2. Characterize sulfate mineral variability with variations in albedo and depositional processes.• 3. Determine if hematite is part of the stratigraphic package or a surface patina to understand history of oxidation state.• 4. Identify targets for best preservation of organic carbon based on composition, permeability, and depositional

processes.

Clay layer should project into strata here

Strata to test for variations in mineralogywith depositional processes.

Test the association of hematite with

stratigraphy

Oblique View1x Vertical

4 Data Credit: NASA/JPL-Caltech/Univ. of Arizona/USGSTuesday, August 21, 2012

Search for Organic Compounds & Understanding Their Preservation• Hypothesis: Diversity of mineralogic compositions and exposure times provides multiple targets for the search for

organic compounds and for characterizing preservation potential whether or not they are present.• Test: Evaluate sample suites with variable mineralogy and different exposure times within a constrained sedimentary

context.• Importance: (of the relationships available here, not of organic carbon detection)

• 1. Suites of samples provide different preservation styles, providing multiple opportunities for organic carbon detection.• 2. Context allows one to characterize processes, whether or not organic compounds are detected.• 3. If organic compounds are detected, context allows detailed hypothesis testing about their origin and preservation.

Sample Suites will Depend on Mineralogical Investigations


More Recently Exposedby Wind Abrasion

Longer Exposure Time

20 m

(same hill)


Changes in Sedimentary Environment & Habitability Through Time• Hypothesis: Multiple processes affected deposition, erosion, and alteration of sediments, and the habitability of multiple

environments can be assessed in the lower layers of Mt. Sharp.• Test: Characterize sedimentary structures, texture, elemental composition, and mineralogy of (from oldest to youngest): • 1) Layered mound sediments; • 2) Fluvial sediments deposited at the mouth of the canyon; • 3) “Mound Skirting Unit” of Anderson and Bell (2010). Compare to fan deposits and high thermal inertia unit in ellipse.

• Importance: • 1. Multiple environments can be characterized across an extended period of time.• 2. Water chemistry varied (hydrous mineral variations), providing diversity in chemical environment.• 3. Provides tests for specific hypotheses related to larger scale predictions for mound sedimentation.

“Mound Skirting Unit” lacking sulfate & clay mineral signatures(alteration of sediment during ancient weathering event?)

Mt. Sharp strata reflecting ancient environments

Sediment deposited by fluvial activity



Water Cycling Between Hydrous Minerals & Atmosphere• Hypothesis: Small amounts of water vapor are exchanged between hydrous Mg sulfates (and possibly other hydrous

minerals) and the atmosphere due to diurnal and seasonal temperature changes. (Frost on Opportunity...)• Test: Cataloging variations in relative humidity & surface temperature in time and with local topography; comparing surface

hydration with estimates of H concentration in the upper meter of bedrock; and correlating data to variations in sulfate mineralogy and abundance in surface outcrops.• Importance: • 1. Understand the current water cycle (locally) on Mars.• 2. Refine the conceptual framework for conditions required to raise the activity of water sufficiently to produce a

modern habitable environment.• 3. Understand processes of mineral diagenesis to constrain weathering and organic carbon preservation potential.

Open areas lacking sulfates: Predict low (no) water vapor exchange

Narrow areas with sulfate-rich wallrock: Predict higher water vapor exchange



What We are Doing Now!

•We landed in the ellipse - like we were supposed to!• 7+ km to the science investigations in the previous slides.

•Goal: Reach Mt. Sharp to evaluate habitability and look for organic carbon• 7 km is a long way for a rover that goes a few 10’s m per sol

• Plan: Structure scientific observations so that we start our investigations before reaching the base of Mt. Sharp• Important scientific results can come from studying rocks on the way.

• First Step: Decide where to take our first samples• Evaluate the geology of the landing ellipse•Make a map of rock types• Analyze surroundings with images and ChemCam• Schedule instrument check-outs, check command sequences on the test bed

rover, learn to work as a team.

8


Mapping Efforts and Naming Fun

9Image Credit: NASA/JPL-Caltech/Univ. of Arizona


A name for coming and going...

10Image Credit: NASA/JPL-Caltech/Univ. of Arizona


Hot Names for Rocket Scours: Burnside, Hepburn, Sleepy Dragon and

11Image Credit: NASA/JPL-Caltech/MSSS

Goulburn


Naming Fun: Coronation

12Image Credit: NASA/JPL-Caltech/CNES/IRAP


A Taste of Our ProcessWhat do you see? What do you predict?

How would you test your predictions with Curiosity’s payload?How would results from these tests provide insights into the mission goals?

Mastcam 34 image acquired Sol 3 13 Image Credit: NASA/JPL-Caltech/MSSS


Now convince your team members to implement your plan!(One of my roles as Long Term Planner is to facilitate the best science in a similar process.)



I was expecting: Adventures in Gale !

• Stellar Mineralogical Story

• Intriguing Potential for Organic Carbon

• Environmental Record of Changing Habitability

• Exploration of the Modern Water Cycle

•Many Unexpected Findings Expected - in a beautiful field site.

5 m1x Vertical; HiRISE images

and elevation model 15 Data Credit: NASA/JPL-Caltech/Univ. of Arizona/USGSTuesday, August 21, 2012

Now we are there!(and the images are so beautiful they bring tears to my eyes)



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