12.158 Lecture 10
Molecular Biosignatures:
Real and Potential Biomarkers, Analytical Innovations,
Meteorites & Old Rocks
http://marsprogram.jpl.nasa.gov/msl/
1
http://marsprogram.jpl.nasa.gov/msl/
2
PAH proposed to
be
molecular fossils ?
RESEARCH ARTICLE
Search for Past Life on Mars:
Possible Relic Biogenic Activity
in Martian Meteorite ALH84001
David S. McKay, Everett K. Gibson Jr.,
Kathie L. Thomas-Keprta, Hojatollah Vali,
Christopher S. Romanek, Simon J. Clemett,
Xavier D. F. Chillier, Claude R. Maechling and Richard N. Zare
This image has been removed due to
copyright restrictions.
‘ PAH are abundant as
fossil molecules in
ancient sedimentary
rocks ’
However, PAH are not necessarily
biogenic
3
Topics
• What are useful criteria for biogenicity?
How can we be sure of measuring the right thing in a sample
on Mars or returned from Mars?
• Analytical methods for investigating molecular
biosignatures in rocks from Earth & elsewhere
4
Report of the NASA Biomarker Taskforce 2000
This image has been removed due to copyright restrictions.
Molecules, isotopes, microfossils, mineral fabrics
Roger Summons, Pierre Albrecht, Sherwood Chang,
Gene McDonald and J. Michael Moldowan
5
Assumptions
• Extra-terrestrial life will resemble earthly life –
based on carbon chemistry operating in an aqueous
environment
- carbon is the only element that is sufficiently abundant, ubiquitous
and chemically suited for life
• It will process chemicals for carbon and energy, make
copies of itself, be autonomous and evolve in concert
with its environment
• Biochemical pathways will operate as above
– comprise energy yielding and replication reactions
– construct complex molecules from simple, universal precursors
– evolve
6
Abiotically produced organic materials
Organic acids and diacids, amino acids, hydroxy
acids, alcohols, amines
• n- and branched-hydrocarbons incl. methane
• Aromatic hydrocarbons (PAH)
Message: Biological organic materials are patterned
Building Blocks� 20 amino acids, 4 bases, 2 lipid types…….
7
Intrinsic Characteristics (Patterns) of
Terrestrial Molecular Biosignatures
•
•
•
•
•
•
Enantiomeric excess
Diastereoisomeric preference
Constitutional isomer preference
Repeating constitutional sub-units or atomic ratios
Systematic isotopic ordering at molecular and intramolecular levels
Systematic distribution patterns or clusters (e.g. C-number,
concentration, d13C) of structurally related compounds
8
Enantiomers of Alanine
H
H2N
C
H
H3C
CH3
COOH
C
NH2
HOOC
L-alanine
D-alanine
L-amino acids predominate in biology
L-amino acid XS in Murchison meteorite
((Eng
gel & Macko a-aa’s; Cronin & Pizzarello non-p
protein aa’s))
Non-biological processes can yield enantiomeric excess
Asymmetric catalysis and autocatalysis
Soai & Sato: slight chiral excess propagated during autocatalytic syntheses
Pizzarello and Weber: AA enantiomeric excess promotes asymmetry in aldol
condensations of glycoaldehyde
9
Stereoisomerism in Tartaric Acid
H
OH
C
HOOC
COOH
HOOC
H
C
H
A (meso)
HO
H
C
C
OH
H
H
COOH
B
C
C
OH
HOOC
COOH
OH
OH
C
B & C enantiomers A & B and A & C are diastereoisomers
Life makes a limited number of all the possible
di
diastereoisomers
i
10
Stereoisomerism in Cholesterol
20
13
14
9
10
3
17
8
H
H
HO
28 stereoisomers
i
possible
ibl ffor cholesterol
h l
l
Biology (ie Eucarya) makes only one
Studies of hydrocarbons as old as 2700 Myr show no deviation of sterane
or hopane stereoisomer patterns; the fossils had the same precursors as
exist today
11
Information Preserved in Products of Diagenesis:
The Sterol Pathways
Unique sterol configuration of living organisms
8 sites of asymmetry
28 = 256 feasible isomers
but only 1 in nature
R
αα (20R)
sterenes and steranes
immature
sediments
aa20R
R
20
o17
rearranged
d steranes
aromatic steranes
o
o
o
14
HO
R
R
R
R
o
o
o
o
ββ (20S)
ββ(20R)
ҏ
o
αα(20S)
ҏ
Complex sterane mixture in mature sediments & oil
12
Constitutional Isomers
OH
OH
OH
Geraniol
Myyrcene
Nerol
C10 compounds (monoterpenes)
- life makes a specific subset of all the
possibilities
(S)-Ipsenol
Pine beetle pheromone
Choleoptera: Scolytidae
O
O
(1S) ( ) β Pinen
(1S)-(-)-β-Pine
ne
e
OH
(1R,2S,5R)-(-)-Menthol
(S)-(-)-Limonene
Cineol (eucalyptol)
O
(1R)-(+)-α-Pinene
13
(1R)-(+)-Camphor
Constitutional Isomers
α β γ δ ε ζ
HOOC - C - C - C - C - C - C
2
or OH
X = NH
Small molecules identified in the Murchison
Meteorite tend to occur with the maximum number
of possible theoretical isomers
e g monoamino monocarboxylic acids and monohydroxy
e.g.
monohydroxy,
monocarboxylic acids (Cronin et al. 1993)
14
Constitutional Isomers
α β γ δ ε ζ
HOOC - C - C - C - C - C - C
X = NH 2 or OH
C-atoms
α
β
γ
δ
ε
ζ
unknown
2
1, 1, 1
--
--
--
--
--
--
3
1, 1, 1
1, 1, 1
--
--
--
--
--
4
2, 2, 2
2, 2, 2
1, 1, 1
--
--
--
--
5
3, 3, 3
6, 6, 3
3, 3, 3
1, 1, 0
-­
--
1
6
8 8,
8,
8 8
12 3,
12,
3 1
11 4,
11,
4 0
4 2 ,0
4,
0
1 1,
1,
1 0
--
2
7
18, 18, 12 29, 0, 0
29, 0, 0
20, 0, 0
5, 0, 0
1, 0, 0
2
15
Acetogenic Lipids & Polyisoprenoids
11
7
3
OH
Life makes a limited number of all the possible constitutional isomers
because it :
- has evolved ‘universal’ biochemical pathways
- constructs macromolecules from small, common
precursors
(eg 20 amino acids in protein, 4 bases of DNA)
Æ Æ preference for certain carbon numbers (clusters) & systematic isotopic
ordering within & between molecules
16
Clusters of compounds
C15
‘cluster
cluster’
- example of a leaf wax
isoprenoids
‘‘odd
dd over even’’
C29-C33 ‘cluster’ of
n-alkanes
C20
‘cluster’
H
OH
isoprenoids
HOOC H
H
H
COOH
H
C
OH
HOOC H
C
HO
C
20
30
40
C
C
OH
COOH
OH
HOOC OH
B
10
COOH
C
50
60
70
min
Clustering is a consequence of universal biochemical pathways
17
Clusters of Compounds
- example of a sediment
‘odd over even’
C29-C33 ‘cluster’
of n-alkanes
n alkanes
C20
‘cluster’ of diterp
penes
C30 and C35
‘clusters’
25.00
30.00
35.00
40.00
45.00
50.00
55.00
NB clustering is ‘blurred’ by mixed inputs, diagenesis, catagenesis
18
Isotopic
Ordering
P l isoprenoid
Polyi
id lilipid
ids
This image has been removed due to
copyright
right restrictions
restrictions.
Polymethylenic
= acetogenic lipids
Isotopic ordering is a
consequence of the
universality of biochemical
path
thways
Hayes J. M. (2002) Fractionation of the isotopes of carbon
and hydrogen in biosynthetic processes. In: Stable Isotopic
Geochemistry, Valley J. W. and Cole D.R. (eds.) Reviews
19
in Mineralogy and Geochemistry.
Acetogenic Lipids
CH3
Ⴠ C O
+ CO2
O
‘heavy’
‘light’
CH3
Ⴠ C SCoA
O
+ CO2
O
Acetate Methyl-C and Carboxyl-C are isotopically distinct and determined
by its metabolic source and the profound isotope effect of pyruvate
deh drogenase
dehydrogenase
20
Origin of C-Atoms in Polyisoprenoids & Consequent
I t ic Ord
Isotopi
deriing
Observing this at natural abundance presently a challenge
21
n-Alkane Carbon Isotop
pes in Oils
12
14
16
18
20
22
24
26
28
30
32
-33.00
-34.00
13
δ
-35.00
Suwaihat-8 Unk Str
Sakhiya-1 A3C
Qashoob-1 A2C
Budour NE-1 A4C
Hudaira-1 A5C
Budour NE-2 A1C
Dhahaban East-2 A1C
-36.00
36 00
-37.00
-38.00
-39.00
Carbon Number
22
RESEARCH ARTICLE
Search for Past Life on Mars:
Possible Relic Biogenic Activity
in Martian Meteorite ALH84001
David S. McKay, Everett K. Gibson Jr.,
Kathie L. Thomas-Keprta, Hojatollah Vali,
Christopher S. Romanek, Simon J. Clemett,
Xavier D. F. Chillier, Claude R. Maechling and Richard N. Zare
PAH proposed to
be
molecular fossils ?
‘ PAH are abundant as
fossil molecules in
ancient sedimentary
rocks ’
This image has been removed due to
copyright restrictions.
However, PAH are not necessarily
biogenic
23
μL2 MS of Murchison Meteorite
Murchison
202
Pyrene/
1.2
178 Fluoranthene
1.0
Phenanthrene/
Signal Intensity
Anthracene
Dominance of
2-4 ring parent PAH
otherwise similar
to ALH84001
0.8
128
0.6
Naphthalene
0.4
Chrysene/
Benzo(a)anthracene
0.2
Benzo(a)pyrene/
Benzo(b/k)fluoranthene
-0.0
-0.2
50
100
150
200
250
300
350
Mass (amu)
Feb 1, 99
24
Murchison
11
1.1
1.0
0.9
Alkylation
Alk
l ti d
drops exponentially
ti ll
ie no ‘clusters’
Relattive Abund
dance
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0
0
-1
0
1
2
3
4
5
6
Number of Carbons attached to Phenanthrene
Feb 1, 99
25
PAH Proposed
p
as molecular fossils ?
PHENANTHRENE
178
1,7-DIMETHYL­
PHENANTHRENE 206
1-METHYL­
PHENANTHRENE 192
1,2,5-TRIMETHYL­
NAPHTHALENE 156
RETENE
234
PHYLLOCLADANE
R
R3
R4
R1
26
R2
δ13C Murchison organic compounds
40
aromatic hydrocarbons
aliphatic hydrocarbons
carboxylic acids
sulphonic acids
amino acids
30
20
10
δ13C
‰PDB
0
-10
Sephton et al., 1998
Cooper ett al.,
l 1997
Gilmour and Pillinger 1994
Engel et al., 1990
Pizzarello et al., 1991
Yuen et al
al., 1984
-20
-30
-40
0
5
10
15
20
25
carbon number
Compilation
courtesy of Mark Sephton
27
Topics
• What are useful criteria for biogenicity?
How can we be sure of measuring the right thing in a sample
on Mars or returned from Mars? Deliberations of the 2000
NASA Biomarker Taskforce – molecular biosignatures
• Analy
ytical methods for investiggating
g molecular
biosignatures in rocks from Earth & elsewhere
• New ‘technologies’ in molecular biosignatures for
organisms and ancient environments
28
OMR017
Buah Fm.
29
Nelson, Reddy, Freysinger + MIT, unpublished
Loop-Jet Modulator
Injector
Cold Jet
Detector
Hot Jet
1st Column
nonpolar
Delay loop
2nd
Column polar
Blank 0.8 meters
Rtx-1 6.5 meters
BPX-50 0.8 meters
Image by MIT OpenCourseWare.
30
OMR017
Buah Fm
a
b
c
d f
e
g
h
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k
k.
l.
m.
31
i
j
k
l
m
17˞ + ˟ + QRUKRSDQH
17Į(H),21ȕ(H)-hopane
17Į(H),21ȕ(H)-29-homohopane 22S
17Į(H),21ȕ(H)-29-homohopane 22R
gammacerane
( ),
( )
p
22S
17Į(H),21ȕ(H)-29-bishomohopane
17Į(H),21ȕ(H)-29-bishomohopane 22R
17Į(H),21ȕ(H)-29-trishomohopane 22S
17Į(H),21ȕ(H)-29-trishomohopane 22R
17Į(H),21ȕ(H)-29-tetrakishomohopane 22S
17Į(H) 21ȕ(H) 29 tetrakishomohopane 22R
17Į(H),21ȕ(H)-29-tetrakishomohopane
17Į(H),21ȕ(H)-29-pentakishomohopane 22S
17Į(H),21ȕ(H)-29-pentakishomohopane 22S
Nelson, Reddy, Freysinger + MIT, unpu
20 Carbons
19 Carbons
18 Carbons
17 Carbons
16 Carbons
OMR011 - Thuleilat
Th l il t Fm
F
15 Carbons
14 Carbons
32
Nelson, Reddy, Freysinger + MIT, unp
55
Cyclohexane + n-C12
82
2.5
67
88
97
252
50
100
150
200
250
89
90
91
M+ 252 = C18
300
Nelson,33 Reddy, Freysinger + MIT, unpublished
Alkylcyclohexane
e + Alkylcyclopentane Peak Volume
e
2000
1600
1200
800
400
OMR011 - Thuleilat Shale
OMR017 - Buah Shale
0
12
13
14
15
16
17
18
Total Carbon Number
34
19
20
21
22
23
3
Ra
atio (Alkylcyyclohexane//Alkylcyclopentane)
2.5
OMR011 - Thuleilat Shale
OMR017 - Buah Shale
2
1.5
odd
dd chains
h i >> even chains
h i
1
0.5
0
13
14
15
16
17
18
Total Carbon Number
35
19
20
21
22
23
Topics
• What are useful criteria for biogenicity?
How can we be sure of measuring the right thing in a
sample on Mars or returned from Mars? Deliberations of
the 2000
NASA Biomarker Taskforce – molecular
biosignatures
• Analytical methods for investigating molecular
biosignatures in rocks from Earth & elsewhere
GC2-TOFMS
Hydropyrolysis & Strelley Pool Chert
36
Biogenic Gases
Mars atmosphere:
This image has been removed due to copyright restrictions.
CO2
N 2,
Ar
CO
O2
H 2O
95.3%
2.7%
1.6%
0.07%
0.13%
0-300 ppm
N2O, H2S, DMS, ethylene ??
CH4 ppb � seasonally and spatially variable
(Mumma et al., Science 323, 1041, 2009)
37
Taphonomy - Preservation Windows
Biosignature
taphonomic window
Confidence
in context
atmospheric gases
crystalline sedimentary
mineral entrainment of
organic compounds
biofabric lithification
exceptional
very high
body fossil preservation
very high
mineral replacement of
body fossil
high
very high
38
How this informs about
potential biosignature
preservation
predictable via chemical modeling
can deduce formation mechanism
and subsequent history
can deduce history from lithology
& stratigraphic relationships
can deduce history from lithology
and stratigraphic relationships
can deduce from mineralogy
Taphonomy: The Role of Sediment Lithology
OM preservation by physical protection (Hedges, Keil, Mayer 1990s)
Data for coastal
sediments:
C = clay
L= silt
S = sand
B= bulk
This image has been removed due to
copyright restrictions.
Organic matter concentrations strongly correlate with mineral surface area (or
small clay particles). As degradation proceeds an increasingly large fraction
of the remaining organic matter is protected by its association with mineral
surfaces .
Hedges and Keil, 1995
39
Biosignature Formation & Preservation
Table 3:
ID by remote sensing
Martian context -->
Early Mars
Environment
Hydrothermal (<100C)
subsurface
Hydrothermal (<100C)
surface
Aeolian sediments
(sand)
altered aeolinites (dust)
Fluvial channel
Fluvial floodplain
alluvial fan
Deltaic
Lacustrine (perennial)
Lacustrine (evaporitic)
(Cl)
Lacustrine (evaporitic)
(SO4)
Regional Groundwater
pore system
Glacial deposits
permafrost
soil (surface fines
chemically altered by
atmosphere )
Pyroclastic Deposits
(unaltered)
Volcanic flows
Regolith/Fractured
Bedrock (not soil)
Support Support for Support
Biotic C
Abiotic C
Carbon
formation formation
Conc
Potential
Support
for Recent geomor minera stratigr
Preservation Exhumation phic
logic
aphic ID by MSL
modlow
mod
low
mod
high
n/a
high
modmod-high
mod
mod
high
high
low
high
mod
mod (F/T)
high
low
low
low
low
low
low
high
n/a
mod
high
very low
low
low-mod
low
high
high
low
low
low
low
low
low
low
low
mod
low
high
high
low
low
mod
low
high
high
low
high
possible
low
low
high
low
high
high
high
high
mod
n/a
n/a
n/a
n/a
n/a
mod
n/a
high
high
high
high
mod
high
high
high
high
high
high
med
low
high
high-very high
high
mod
high
mod
high
low
low
high
high-very high
high
mod
high
mod
high
low
low
low
low
low
low
low
low
low
low
low
mod
high
high
mod
n/a
high
high
n/a
n/a
n/a
n/a
low
n/a
mod
high
high
n/a
high
low
low
low
low
low
n/a
n/a
(albedo
and TI)
low
very low
low
low
low
low
low
low
low
low
mod
high
low
high
high
mod
high
high
low
low
low
low
low
high
n/a
n/a
high
40
Biosignature Formation Processes
Table 3:
ID by remote
sensing
Support
Potential
for Recent
Martian context -->
Support for Abiotic Support
C
Exhumatio geomor miner stratigr
Early Mars
Biotic C
Carbon
Support
n
Environment
formation formation Conc Preservation
phic alogic aphic
Hydrothermal
(<100C) subsurface
mod
mod (F/T)
low
mod
low
Hydrothermal
(<100C) surface
high
low
modhigh
mod
Aeolian sediments
(sand)
low
low
low
Fluvial channel
low
low
low-mod
Deltaic
Lacustrine
(perennial)
Fluvial floodplain
ID by
MSL
mod
modhigh
n/a
high
mod
high
modhigh
low
high
low
low
high
n/a
mod
high
low
low
high
high
n/a
high
high
low
mod
mod
possible
high
n/a
high
high
high
low
high
high
low
high
n/a
high
high
high
low
high
high
high
mod
mod
mod
high
41
Biosignature Formation Processes
Table 3:
ID by remote
sensing
Martian context -->
Early Mars
Environment
Hydrothermal
(<100C) subsurface
Support
Potential
for Recent
Support for Abiotic Support
C
Exhumatio geomor minera stratigr
Biotic C
Carbon
Support
n
formation formation Conc
Preservation
phic
logic
aphic ID by MSL
low
high
low
modhigh
mod
mod
Aeolian sediments
(sand)
low
low
low
low
low
high
n/a
mod
high
Fluvial channel
low
low
low
low
high
high
n/a
high
high
low-mod
low
mod
mod
possible
high
n/a
high
high
high
low
high
high
low
high
n/a
high
high
high
low
high
high
high
mod mod mod
high
Fluvial floodplain
Deltaic
Lacustrine
(perennial)
mod
42
low
mod
modhigh
mod (F/T)
Hydrothermal
(<100C) surface
mod
n/a
modhigh high low
high
high
Lost City Hydrothermal Field
Vent Fluids
Hydrogen – up to 15 mmol/kg
Methane – up to 2 mmol/kg
This image has been
removed due to copyright
restrictions.
Calcium – up to 30 mmol/kg
pH – 9 to 11
Low temp volatile production: Proskurowski et
al., Chem. Geology 2006
Abiogenic Hydrocarbon Production at Lost
City Hydrothermal Field:
Proskurowski et al., Science 2006
Amend, Hoehler, McCollom AbSciCon 2010
43
13δ
LC methane suggests it is abiogenic
Courtesy Elsevier, Inc., http://www.sciencedirect.com. Used with permission.
44
13δ
LC methane suggests it is abiogenic
Structure & δ13C LC lipids show methane
production is also biological
Fluids
CH4
DIC
Carbonates
Fatty acids
Archaeal
Lipids
Abundant
Glycerol monoethers
Glycerol diethers
Archaeols
-80
-70
-60
-50
-40
-30
13
δ C, ‰
-20
-10
0
10
Bradley et al., GCA 2009
Courtesy Elsevier, Inc., http://www.sciencedirect.com. Used with permission.
45
Murchison
202
1.2
Pyrene/
Fluoranthene
178
10
1.0
0.8
Dominance of
2-4 ring parent PAH
0.6
otherwise similar
to ALH84001
Phenanthrene/
Signal Intens
sity
Anthracene
128
Naphthalene
0.4
Chrysene/
Benzo(a)anthracene
0.2
Benzo(a)pyrene/
Benzo(b/k)fluoranthene
( )
-0.0
-0.2
50
100
150
200
250
300
350
Mass (amu)
Feb 1, 99
46
Topics
• What are useful criteria for biogenicity?
How can we be sure of measuring the right thing in a sample
on Mars or returned from Mars? Deliberations of the 2000
NASA Biomarker Taskforce – molecular biosignatures
• Analy
ytical methods for investiggating
g molecular
biosignatures in rocks from Earth & elsewhere
GC2-TOFMS
• New ‘technologies’ in molecular biosignatures for
organisms and ancient environments
47
Hydropyrolysis (H2)
thermocouple
Murchison
high pressure
hydrogen
electrical
connectors
reactor tube
sample
• sample impregnated
- ammonium dioxydithiomolybdate
gas collection
and measurement
- decomposes above 250 ºC to catalyst
• continuous high flow of H2
• heated 220 to 520 ºC
• dry ice trap
• dichloromethane
cold
trap
pressure
transducer
Hydropyrolysis facilitates breakdown of macromolecules & minimises rearrangement
48
δ13C profiles for HyPy products of 3 meteorites
5
Murch
0
-5
-10
-15
-20
-10
Orgueoil
-15
-20
diMeth
diM
thylbi
lbiph
henyll
-10
-15
-20
800
4H-naphthalene
Acenaphthene
methyl-biphenyl
Phenathrene/anthracene
1000
1200
1400
Retention time, sec
49
1600
Pyrene
Cold Bokk
-5
Methylpyre
enes
-25
Fluoranthene
13
δ C values(¡ë, VPD
DB)
-25
1800
n Alkanes in Meteorites
n-Alkanes
-5
-10
-15
Orguiel (CI1)
Vigarano (CV3)
Cold Bokkeveld (CM2)
Ornans (CO3)
Murchison (CM2)
Bishunpur (LL3)
n-alkane-po
oor aliphatic
c fraction
h aliphatic frraction
n--alkane-rich
Petro
oleum n-alkanes
Petrole
eum
13
δ C
-20
-25
δ13C
PDB(‰)
-30
-35
-40
-45
Sephton et al., 2001
Stahl 1979
Bjoroy et al., 1991
Krishnamurthy et al., 1992
-50
12
14
16
18
20
22
carbon number
50
24
26
Microbes: Comparison of alkyl chain lengths (m/z 85)
18
Prochlorothrix hollandica
16
14 15 17
1617 18
Phormidium luridum
15
16
18
Chlorobium
31
thiosulfatophilum
20
17
16
15
13
Methylococcus capsulatus
14
Ph
Halobacterium saccharovorum
Pr
16
17 Ph
16 18
Phormidium ‘RCO’
15
Emiliania huxleyi
18
31
22
16
33
14
16
3738
Scenedesmus quadricauda
18
26
28
30
32
Retention Time
51
bacteria
archaea
algae
black chert veins and clasts
Complex
p ‘Dyke’
y Breccia
52
53
SPC 16 Kerogen sequential HyPy
TICs
12
100
330 HyPy
16
14
13
15
%
18
17
Pr?
0
100
Ph?
99% PAH & 70% alkanes in
HT fraction
520 HyPy
H P
13
14
Magnet EI+
15
%
16
17
12
Phen
18
Py
19
20
12.44
0
12.50
15.00
17.50
20.00
22.50
25.00
27.50
30.00
32.50
35.00
37.50
40.00
42.50
45.00
47.50
Small EOP of n-alkanes in low T fraction probably indicates some younger
contamination e.g. produced from reduction of even C no. fatty acids.
54
Time
50.00
Distribution of aromatic hydrocarbons from HyPy
CM 001 aro re-sep
04 Dec 01 10
100
%
MeN
P
Magnet EI+
TIC
1.19e5
McArthur River (HYC)
MePPy MePy
N
Ch
complex- more alkylated
B(e) B(ghi) more complex
Py Per
Co
MeCo
0
20.00
30.00
CM 003 Aro
40.00
50.00
60.00
70.00
80.00
90.00
Py
04 Dec 01 05
100
Time
100.00
Magnet EI+
TIC
8.38e4
Strelley Pool
%
P
MeP
MePy
Ch
b(e)
Py
B(ghi)
Per
9
Time
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
m/z 178+192
P
MeP/P = 0.82
100
0.9
MeP
CM003
2
3
%
Py
100
2
Fla
%
0.8
91
R = 00.9257
9257
MePys
0.7
0
04 Nov 18 16
0
M e P /P r a tio
Dec
creasing atomic H//C
m/z 202+216
0.6
100
100
MeP/P = 0
0.70
70
CM002
0.5
%
%
0.4
MeP/P and MePy/Py reflect bulk
kerogen atomic H/C;
0.
0
0
04 Nov 18 15
0.2
100
100
CM004
δ13C
%
0
24.00
MeP/P = 0.35
Fla
0.1
%
or [9+1]/[3+2] may ultimately0 help discriminate biology
25.00
26.00
27.00
28.00
29.00
30.00
31.00
32.00
33.00
34.00
35.00
Time
36.00
0
00.11
00.22
0.3
03
H/C atomic ratio
Fla = fluoranthene
Py = pyrene
MePy
y = methylpyrenes
y py
P = phenanthrene
MeP = methylphenanthrenes
56
0.4
04
0.5
05
0
me
Time
Ti
30.00
30.00 31.
31.00
00 32.00
32.00 33.
33.00
00 34.00
34.00 35.
35.00
00 36.00
36.00 37.
37.00
00 38.00
38.00 39.
39.00
00 40.00
40.00 41.
41.00
00 42.00
42.00 43.
43.00
00 44.00
44.00 45.
45.00
00
Concluding Thoughts
1. Organic compounds made by terrestrial organisms have generic
structural & isotopic traits. Searching for these features in
exttratterresttriiall OM iis a sound
d approachh tto lif
life ddettection.
ti
2. Terrestrial sediments as old as 2700Ma contain an abundance of
molecular biosignatures
biosignatures’. Lipid biosynthetic pathways are of great
‘molecular
antiquity & there is no evidence for there having been alternative
pathways or extinct pathways.
3. Hydrocarbons are robust and, of all compound classes, are likely to
be preserved under harsh conditions so long as they are sterile.
Emergiing tech
t hnollogiies suchhas mu ltidimensi
ltidi
ionall GC andd GC
GC-TOF
TOF
are useful analytical tools.
4. Hyropyrolysis assists screening for biosignatures in
macromolecular OM and biomass
57
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12.158 Molecular Biogeochemistry
Fall 2011
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58