Astrobiology Workshop 2013/11/28
Unique Late Archean Atmosphere
Enhanced Volcanic and Biological Activities
Yuichiro Ueno1,2*
Sebastian O. Danielache3
Yoshiaki Endo1
Matthew Johnson4
Carbonyl sulfide (OCS)
1Department
of Earth & Planetary Sciences, also at
2Earth-Life Science Institute (ELSI), Tokyo Institute of Technology, Japan
3Faculty of Science & Technology, Sophia University, Japan
4Copenhagen Center for Atmospheric Research, Univ. Copenhagen, Denmark.
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Early Earths = Inhabited Different Planets
O2
CO2 ?
CH4?
+∆33S:
33S-rich
relative to normal
mass dependent relation
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after
Johnston
2011
Sulfur: Key for Early Atmosphere
∆33S = δ33S - 0.5 δ34S ≠ 0
SO2 photolysis is known to produce
the anomaly & important in O2-free
early atmosphere
Late Archean record is unique
Q: Why ∆33S scatter?
O2
+∆
−∆
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is provided
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after
Johnston
2011
CH4-rich Atmosphere (Late Archean)
Pinti & Hashizume (2010)
• Biological scenario (Methanotrophy)
CH4 + O2 （or SO4） → energy
CH4 → organic carbon （low δ13C)
Anoxic world + Oxidant input
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Link with Increasing Volcanic Activity ?
Large Igneous Provinces (LIPs) through time
Fortescue LIP @ 2.8~2.6 Ga
Ernst (2007)
Pirajino (2004)
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Numerical Simulation
・ Inject 10 ppm SO2 @ t=0
・ Tracing the fate of SO2
injected into CH4-rich atmosphere
by intense volcanic eruption
Model
・ >600 reactions (C-H-O-S chemistries)
>1500 when including S isotopes
・ Fixed background species:
N2:
1 bar
CO2: 1%
CO:
0.1%
H2:
0.01%
・ Redox change
CH4: 10 ppm – 1%
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Fate of injected SO2
CO2 atmosphere:
CO2 + CH4 atm. :
H2SO4 (small ∆33S)
OCS (>H2S>S0) + H2SO4 (large ∆33S)
Ox.
Red.
CH4= 10ppm
CH4= 1%
10 ppm SO2 injected into 1bar N2 , 1% CO2, 1ppm H2 atmosphere
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Fate of injected SO2
CO2 atmosphere:
CO2 + CH4 atm. :
Why OCS ?
H2SO4 (small ∆33S)
OCS (>H2S>S0) + H2SO4 (large ∆33S)
*high [S] & [CO] in reducing CH4 atm.
SO2 ＋ hν → SO ＋ hν → S
CO2 ＋ hν → CO + O
S ＋ CO ＋ M → OCS + M
Elevated OCS requires
1) Reducing atmosphere (CH4/CO2 > 0.1)
2) High SO2 flux into atmosphere (>6x1011 mole/year = 3 x today’s volcanic flux)
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Summary: fate of injected SO2
Previous model
SO2
-∆
-∆
H2SO4
BaSO4
UV
SO
+∆
S0
+∆
FeS2 +∆
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Summary: fate of injected SO2
CO2 (oxidizing) atm.
SO2
-∆
H2SO4
UV
SO
+∆
+∆
OCS, H2S, S0
-∆
SO42-
HS-
-∆
BaSO4
FeS2 +∆
+∆
* Small ∆33SSO4
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Summary: fate of injected SO2
CO2 (oxidizing) atm.
SO2
-∆
H2SO4
CO2+CH4 (reducing) atm.
SO2
UV
SO
-∆
H2SO4
+∆
UV
+∆
Atmospheric OCS reservoir
when (1) high volcanic SO2 flux
(2) reducing (CH4) atm.
SO
+∆
OCS, H2S, S0
-∆
SO42-
HS-
+∆
-∆
SO42-
-∆
BaSO4
FeS2 +∆
-∆
BaSO4
* Small ∆33SSO4
Sulfate
reduction
-∆
FeS2
OCS Long 2life time
(> 10 day)
> H2S
> S0 +∆
HS-
+∆
FeS2
+∆
* Large variation of ∆33SSO4 & ∆33Ssulifde
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Ox.
CO2
Red.
CH4/CO2
CO2 ?
?
?
CH4
OCS
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is provided
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after
Johnston
2011
Archean record: ∆36S/∆33S = ~ -1
Archean
3500-2500 Ma
BaSO4
・∆33S = δ33S -0.515 δ34S
・∆36S = δ36S -1.90 δ34S
CAS
Sulfide
∆36S/∆33S : unlikely changed after photolysis
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∆33S-SO: Spectroscopic Prediction (revised)
Model
Experiment
SO2
-∆
H2SO4
UV
Isotope
Effect
SO
+∆
OCS, H2S, S0
-∆
-∆
SO42BaSO4
HS-
+∆
FeS2 +∆
Danielache et al. (2008 JGR)
FTUV
Our previous
Cross section
measurement
32SO
Dual beam
monochromater
33SO ,
,
2
2
34SO
2,
36SO
2
Endo et al. (in prep.)
+Pressure effect
correction
*higher accuracy
for σ
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∆33S-SO: Spectroscopic Prediction (revised)
Model
Isotope Effect
SO2
-∆
H2SO4
UV
Isotope
Effect
SO
32/33/34/36 J
(photolysis rate) =
32/33/34/36σ (cross section) x I (UV flux)
+∆
Solar Spectrum
Ι
OCS, H2S, S0
-∆
SO42-
HS-
+∆
Cross section
σ
33σ
34σ
36σ
Endo et al. (in prep.)
32
-∆
BaSO4
FeS2 +∆
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∆33S-SO: Spectroscopic Prediction (revised)
Model
Solar UV SO2 photolysis (no shielding effect)
SO2
-∆
H2SO4
UV
Isotope
Effect
SO
+∆33S Product SO & OCS, H2S, S
+∆
OCS, H2S, S0
-∆
SO42-
HS-
-∆
BaSO4
FeS2 +∆
+∆
This document is provided by JAXA.
∆36S-SO: Spectroscopic Prediction (new result)
Model
Solar UV SO2 photolysis (no shielding effect)
SO2
-∆
H2SO4
UV
Isotope
Effect
SO
∆36S/∆33S = ~ -1
+∆
OCS, H2S, S0
OCS-shielding
CO2shielding
-∆
SO42-
HS-
-∆
BaSO4
FeS2 +∆
+∆
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Archean MIF: ∆36S/∆33S = ~ -1
Archean
3500-2500 Ma
BaSO4
・∆33S = δ33S -0.515 δ34S
・∆36S = δ36S -1.90 δ34S
CAS
Sulfide
∆36S/∆33S : unlikely changed after photolysis
This document is provided by JAXA.
Summary
Late Archean
(1) high volcanic SO2 flux
(2) reducing (CH4) atm.
result in S differentiation into
Atmospheric OCS & Ocean SO4
New SO2 spectra
• high accuracy & precision
• result in ∆36S/∆33S = ~ -1
• Sulfate: –∆33S
roughly reproducing
Archean S-isotope record
CO2+CH4 (reducing) atm.
SO2
-∆
H2SO4
-∆
SO42-
-∆
BaSO4
UV
+∆
SO
Sulfate
reduction
-∆
FeS2
Long life time
(> 102 day)
OCS
> H2S
> S0 +∆
HS-
+∆
FeS2
+∆
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Greenhouse Effect
CO2 < CH4 < N2O < OCS < NH3 (& H2O)
Reducing species:
possibly solving the Faint Young Sun Problem
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Rise of O2: Trigger of 2.3 Ga Snowball Event
O2
?
CO2 ?
CH4
OCS
Huronian Snowball
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is provided
by JAXA.
after
Johnston
2011
Thank you !
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