American Astronautical Society, Astronauts and Robots: Partners in Space Exploration, May 12-13, 2015 - http://astronautical.org/event/astronauts-robots

1. LIFE
?
CLIMATE
BIOSPHERE
?
GEOLOGICAL
PROCESSES &
DEPOSITS
Understand
Mars as a
system

2. AstrobiologyAstrobiology
Concepts of LifeConcepts of Life
in the Contexts of Marsin the Contexts of Mars
informationinformation
storage andstorage and
replicationreplication
energyenergy
harvesting andharvesting and
transductiontransduction
organicorganic
biosynthesisbiosynthesis
EVOLUTIONEVOLUTION

3. solutes
demand
supply
extremes
impose
costs
solubility
Adapted from T. Hoehler

4. Depth(mbsf)
12108642
Log (cells·mL-1
)
● Eq. Pacific
● N.Pac.Gyre
● S.Pac.Gyre
● ODP
● Non-ODP
Biomass Density: Pacific Ocean Sediments
(Kallmeyer et al., AGU 2009)
107.5
x
Productivity modulated by energy availability …

5. (Des Marais et al., 2008)

6. Propagation
is possible
Mars’ surface environment today
(NASA/JPL Special Regions Science Advisory Group, 2006)

10. Open Basin Lakes
N=>210 (~65% newly
recognized)
Fassett and Head, 2008a,b
Noachian Valley Networks and Open Basin LakesAncient Martian Stream Systems and Lakes
Early climates were wetter and perhaps also somewhat warmer

11. NN
BonnevilleBonneville
CraterCrater
ColumbiaColumbia
HillsHills
RegionRegion
BasalticBasaltic
PlainsPlains
ColumbiaColumbia
MemorialMemorial
StationStation
(Lander)(Lander)
HomeHome
PlatePlate
WestWest
SpurSpur
HusbandHusband
HillHill
Spirit’s Traverse
in Gusev Crater

12. Rocks and soils (regolith fines)
within reach
Which ones to focus on?
Targeted Remote Sensing
observations
Which ones to touch?
Contact
observations
Which ones to sample?
samples
Deciphering Geological Processes and History
Quantity of Geologic Observations
After E2E-iSAG
QUANTITY OF GEOLOGIC OBSERVATIONS
“Well documented” means that the appropriate geologic measurements
have been carried out across the exploration area to provide maximum
constraints on the interpretation of the sample analysis.
To ensure that a site, or
samples from it, are “well
documented” requires
using the rover’s tools and
instruments to make a
sufficient quantity, variety
and quality of geologic
observations to interpret
past environmental
conditions and understand
spatial and temporal
relationships in the
geologic record.

13. 06/03/15 132020 Mars Rover Science Definition Team
Scientific Process for Detecting Past Martian Life
POTENTIAL FOR
BIOSIGNATURE
PRESERVATIO
N
EXISTENCE OF
POTENTIAL
BIOSIGNATURE
PRE-CONDITIONS THAT
MUST HAVE BEEN MET
Past conditions
suitable for the
existence of life
at the site.
Past conditions
suitable for the
preservation of
past life in the
geologic record.
An observable
feature that
might be
evidence of past life.
RECOGNITION OF
DEFINITIVE
BIOSIGNATURE
An observable
feature that is
confirmed to be
evidence of past life.
POSSIBLE EVIDENCE
OF ANY PAST LIFE
PAST LIFE
DETECTED
Proposed Mars 2020 Rover
Labs on Earth
MSR
PAST
HABITABLE
ENVIRONMENT
To search for potential biosignatures, it is necessary to (a) identify sites that
very likely hosted past habitable environments, (b) identify high biosignature
preservation potential materials to be analyzed for potential biosignatures,
and (c) perform measurements to identify potential biosignatures or materials
that might contain them.

14. Summary
• Mars system science: address interactions
between geological, climate (and life?)
processes over spatial and temporal scales
• “Habitability” spans orders of magnitude; this
range matters in our search for life
• Integrate observations across broad spatial and
temporal scales: site selection, landed remote
sensing, contact science, sample selection, in-
depth sample analysis
• An optimal human-robot synergy addresses
challenges at all scales of observation
adapted from A. Pohorille

15. LIFE
?
CLIMATE
BIOSPHERE
?
GEOLOGICAL
PROCESSES &
DEPOSITS
Understand
Mars as a
system

16. Biosignatures: What We Look For…
Body
Fossils
Biominerals
Biofabrics
Chemical
Fossils
(Biomarkers)
Stable Isotopes
Des Marais (2014)
Gases
Metabolism

17. End

18. Evolution
(descent with
modification)
Life’s Basic
Functions
Des Marais (2014)

19. Solvent for life
• Life requires self-organization of organic
matter mediated by non-covalent
interactions…
• Interactions must be well balanced;
this implies a high dielectric constant
and a robust solvophobic effect
• The solvent should support life over
sufficiently wide ranges of T & P (& pH?)
• The solvent must be chemically active
adapted from A. Pohorille

21. Mineralogical Traces of Early Habitable
EnvironmentsWater (availability, activity,
composition), Energy (level,
flux), Temp., pH, Salinity
Energy balance analysis
Energy Demand
= f (T, pH, fluid comp.,
self-repair)
Energy Supply
= f (T, pH, fluid comp.,
& host matrix)
(these factors combine to determine
how habitable a system may be)
Extremes in T, pH, salinity, radiation, etc.
impose substantial energy demands
(T. Hoehler, 2011)

23. presence of reduced carbon (e.g., graphite, diamonds)
• Distributions of identifiable molecular structures and/or
components (if macromolecular)
Low
High
presence of organic carbon (compounds with C-H bonds)
• Isomer ratios of amino acids
OM
Detection
ConfidenceScale
• molecular mass distribution of organic components
• compound specific isotopic composition
• aliphatic/aromatic ratio
• organic functionalization (polar/nonpolar)
• C, H, O, S, N, Cl ratios of organic matter
• fine scale OM distribution in materials
Basic molecular bond information
OrganicMatterCharacterization
Different types of organic matter measurements
provide different levels of confidence in a biological
origin for the organic matter (OM)*
Stable isotopic composition of organic carbon
* The level of confidence provided by a given measurement varies depending on the specific
details (e.g. degree of thermal degradation) of the sample being investigated
06/03/15 232020 Mars Rover Science Definition Team

24. Des Marais (2001)