Measurability

1
Biosignatures Detection - depends on formation,
concentration, preservation, and measurability

• Measurability MSL payload instruments
• Based on definitive nature of the biosignature
  and its measurability by the MSL payload
• diagnostic organic molecules
• biogenic gases
• organism morphologies (cells, body fossils,
  casts)
• biofabrics (including microbial mats)
• isotopic signatures
• evidence of biomineralization and bioalteration
• spatial patterns in chemistry

Precedence is given to organic matter (OM)
detection, though, where it occurs, there is a
high probability that other biosignatures may
also be present.
from Table 1, Summons et al., submitted,
Astrobiology
2
Biosignatures Detection - depends on formation,
concentration, preservation, and measurability

• Formation - directly related to past habitability
  assuming past life existed on Mars.
• Water, energy sources (e.g., chemical gradients),
  nutrient supply,
• protection from extreme conditions (i.e.,
  radiation and high heat)
• Concentration - Depositional environments that
  favored sedimentation of OM via retention and
  hydrodynamic concentration
• Same environments favor habitability
• Possibility of closely linked in situ
  biosignature generation and burial
• Preservation - Concentrations of sedimentary
  minerals that protect OM from ionizing radiation
  and chemical oxidation (e.g., phyllosilicates)

Summons et al., submitted, Astrobiology
3
Potential early Mars sedimentary environments
that would support organic C formation,
concentration, and preservation
Early Mars Environment Support for Support for Support for
Early Mars Environment Biotic ( abiotic) Corg formation Corg Concentration Corg Preservation
Aeolian sediments low low low
Regional groundwater pore system low low low
Alluvial Fan low low low
Fluvial channel low low low
Fluvial floodplain low-mod (low) low mod
Deltaic sediments high (low) high high
Lacustrine (perennial) high (low) high high
Lacustrine evaporitic (Cl-) med (low) high high-very high
Lacustrine evaporitic (SO4) low (low) high high-very high
from Table 3 of Summons et al., submitted,
Astrobiology
4
Potential early Mars volcanic and hydrothermal
environments that would support organic C
formation, concentration, and preservation
Early Mars Specific Cases Support for Support for Support for
Early Mars Specific Cases Biotic ( abiotic) Corg formation Corg Concentration Corg Preservation
Pyroclastics aqueous alteration (surface and subsurface) low low mod-high
Volcanic flows- aqueous altered surface low low low-mod
Volcanic flows- aqueous altered subsurface mod low low-mod
Volcanic flows- hydrothermal altered surface mod (low) low mod
Hydrothermal subsurface (lt100 C) mod mod-low mod
Hydrothermal surface (lt100 C) high (low) mod-high mod
Mafic and ultramafic subsurface (lt100 C) high (low) mod-high mod
from Table 4 of Summons et al., submitted,
Astrobiology
5
Habitability/Biosignature Preservation questions
for MSL

1. Cyclic deposits. If there is any repeat
   patterning to the horizontally layered basin
   floor deposits or fan deposits and they contain
   clay-rich layers or salts, then perhaps there may
   be an opportunity for MSL to test for an
   ecological record, like that suggested for Gale.
   Alternatively, variations in lithofacies
   laterally and with respect to the fan system may
   be useful as a framework for investigating
   paleo-ecosystems. 
2. Horizontally layered deposits on the basin floor.
   If these are lacustrine and fine grained, then
   they are an optimal place to search for both
   habitat features and preserved biosignatures. A
   stratigraphic framework of a lacustrine/deltaic
   system would be ideal for characterizing
   habitability and detecting biosignatures but it
   is not required.
3. Delta to basin correlation. If organic matter or
   biosignatures are present in deposits, can we use
   these to help correlate delta to basin strata?

6
Habitability/Biosignature Preservation questions
for MSL

1. Most ancient fluvial deposits. Are there clay or
   salt deposits associated with the more ancient
   fluvial deposits underlying the horizontal
   layered units in the basin floor? If clay layers
   or salts are present, is there organic matter or
   are biosignatures present in them? Is the
   mineralogy or clast composition significantly
   different than younger deposits, differences that
   speak to different habitability?
2. Holden sediments. Do the sedimentary rocks in the
   Holden ejecta suggest differences in the
   habitability conditions of the Holden deposit?
   Are there biosignatures present? Do these rocks
   show alteration associated with the impact event
   (hydrothermal) or later aqueous alteration?

7
Habitability/Biosignature Preservation questions
for MSL

• Clays in Strata Do the light toned layered units
  at the base of the scarp and in horizontal
  layered outcrops on the basin floor have
  clay-bearing units within them (i.e.,
  siltstones/mudstones)? Or is the clay distributed
  within a more poorly sorted sediment? Milliken
  CRISM spectral parameters indicate that both
  swelling and non-swelling (mixed-layer) clay
  minerals may be present at Eberswalde Can these
  different types of clay minerals be related to
  specific localities or deposits? Do they
  correlate to organic matter character and
  biosignatures?
• Missing Salts. Is there a suite of salts present
  in various units? Are they associated with
  fine-grained deposits or clay minerals? Does the
  salt mineralogy tell us about evolution of the
  water chemistry of the lake during water level
  fluctuations? Has the salt been redistributed by
  post-depositional processes? Does the mineralogy
  of salts and clay correlate to organic matter
  character?
• Carbon Cycle. Are their traces of carbonates
  present? If so, are there any isotopic,
  mineralogic, or other measurable variations over
  time (based on stratal relationships)? If so, do
  they relate to depositional changes? How do these
  values compare to atmospheric CO2 and CH4
  C-isotopic compositions?
• Outcropping characteristics for biosignature
  recovery. Does the outcropping of the basin floor
  layered rocks versus the light-toned layered
  rocks at the fan scarp offer any advantages in
  terms of more recent erosional exposure or
  protection from radiation.  For example,
  partially shaded exposures or exposures recently
  exposed (e.g., mass wasting) may exhibit better
  preservation.