Investigations of the photochemical isotope equilibrium between O&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;, CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; and O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;

Shaheen, R.; Janssen, Christof; Röckmann, T.

doi:10.5194/acp-7-495-2007

Cited by 25 publications

(30 citation statements)

References 31 publications

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“…Stratospheric oxygen isotope covariations in CO 2 (8,11,12) consistently differ from those found in laboratory experiments simulating stratospheric photochemistry (6,(13)(14)(15)(16) Table 1). The stratospheric samples display ⌬ 47 values both higher and more variable than those exhibited by tropospheric air at the surface, which has an average ⌬ 47 value of 0.92 Ϯ 0.01‰ in remote regions (Cape Grim, Tasmania and Barrow, Alaska) (18).…”

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confidence: 52%

Large and unexpected enrichment in stratospheric ¹⁶ O ¹³ C ¹⁸ O and its meridional variation

Yeung¹,

Affek

Hoag³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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The stratospheric CO 2 oxygen isotope budget is thought to be governed primarily by the O( 1 D)+CO 2 isotope exchange reaction. However, there is increasing evidence that other important physical processes may be occurring that standard isotopic tools have been unable to identify. Measuring the distribution of the exceedingly rare CO 2 isotopologue 16 O 13 C 18 O, in concert with 18 O and 17 O abundances, provides sensitivities to these additional processes and, thus, is a valuable test of current models. We identify a large and unexpected meridional variation in stratospheric 16 O 13 C 18 O, observed as proportions in the polar vortex that are higher than in any naturally derived CO 2 sample to date. We show, through photochemical experiments, that lower 16 O 13 C 18 O proportions observed in the midlatitudes are determined primarily by the O( 1 D)+CO 2 isotope exchange reaction, which promotes a stochastic isotopologue distribution. In contrast, higher 16 O 13 C 18 O proportions in the polar vortex show correlations with long-lived stratospheric tracer and bulk isotope abundances opposite to those observed at midlatitudes and, thus, opposite to those easily explained by O( 1 D)+CO 2 . We believe the most plausible explanation for this meridional variation is either an unrecognized isotopic fractionation associated with the mesospheric photochemistry of CO 2 or temperature-dependent isotopic exchange on polar stratospheric clouds. Unraveling the ultimate source of stratospheric 16 O 13 C 18 O enrichments may impose additional isotopic constraints on biosphere–atmosphere carbon exchange, biosphere productivity, and their respective responses to climate change.

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confidence: 52%

Large and unexpected enrichment in stratospheric ¹⁶ O ¹³ C ¹⁸ O and its meridional variation

Yeung¹,

Affek

Hoag³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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“…The 1-h extraction was also not performed for sample B, but sufficient sample was recovered at the 12-h time step. The overall uncertainty for the complete procedure (CO 2 acid extraction, gas chromatography, fluorination, and isotope analysis), based on repeated samples similar in size and composition to the Martian rock samples, is ±0.1‰ for δ 13 C and ±0.2‰ for 17 would allow it to preserve its interaction with the modern atmospheric CO 2 through a transition stage at higher temperature, as suggested in previous studies, following the reaction sequence outlined in Fig. 4.…”

Section: Discussionmentioning

confidence: 80%

“…These results indicate the presence of a Ca-rich carbonate phase enriched in 18 O that formed sometime after the primary aqueous event at 3.9 Ga. The phases showed excess 17 O (0.7‰) that captured the atmosphere-regolith chemical reservoir transfer, as well as CO 2 , O 3 , and H 2 O isotopic interactions at the time of formation of each specific carbonate. The carbon isotopes preserved in the Ca-rich carbonate phase indicate that the Noachian atmosphere of Mars was substantially depleted in 13 C compared with the modern atmosphere.…”

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confidence: 79%

“…The exact process responsible for their formation is not clear, although low-temperature aqueous precipitation, biogenic production, evaporation, and high-temperature reactions are all candidate processes (9)(10)(11)(12)(13). Decoding the fingerprints of various oxygen-carrying reservoirs on Mars (atmosphere-hydrosphere-geosphere) and how they interact from δ 18 O alone is nearly impossible because of the lack of direct information on the isotopic composition of the primary O-carrying reservoirs in the carbonate system (CO 2 3 , and H 2 O 2 has been successfully used to investigate physicochemical and photochemical processes in terrestrial and extraterrestrial materials (14)(15)(16)(17)(18). In this study, we used five stable isotopes of carbonates ( 12 C, 13 C, 16 O, 17 O, and 18 O) on Ca-and Fe-rich phases to decipher atmosphere-hydrosphere interactions and Martian CO 2 /CO 3 geochemical cycling.…”

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confidence: 99%

“…Decoding the fingerprints of various oxygen-carrying reservoirs on Mars (atmosphere-hydrosphere-geosphere) and how they interact from δ 18 O alone is nearly impossible because of the lack of direct information on the isotopic composition of the primary O-carrying reservoirs in the carbonate system (CO 2 3 , and H 2 O 2 has been successfully used to investigate physicochemical and photochemical processes in terrestrial and extraterrestrial materials (14)(15)(16)(17)(18). In this study, we used five stable isotopes of carbonates ( 12 C, 13 C, 16 O, 17 O, and 18 O) on Ca-and Fe-rich phases to decipher atmosphere-hydrosphere interactions and Martian CO 2 /CO 3 geochemical cycling. This high-precision multi-O-isotope analysis of secondary minerals was coordinated with detailed petrographic and ion microprobe analyses.…”

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confidence: 99%

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Carbonate formation events in ALH 84001 trace the evolution of the Martian atmosphere

Shaheen

Niles

Chong

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Carbonate minerals provide critical information for defining atmosphere-hydrosphere interactions. Carbonate minerals in the Martian meteorite ALH 84001 have been dated to ∼3.9 Ga, and both C and O-triple isotopes can be used to decipher the planet's climate history. Here we report Δ 17 O, δ 18 O, and δ 13 C data of ALH 84001 of at least two varieties of carbonates, using a stepped acid dissolution technique paired with ion microprobe analyses to specifically target carbonates from distinct formation events and constrain the Martian atmosphere-hydrosphere-geosphere interactions and surficial aqueous alterations. These results indicate the presence of a Ca-rich carbonate phase enriched in 18 O that formed sometime after the primary aqueous event at 3.9 Ga. The phases showed excess 17 O (0.7‰) that captured the atmosphere-regolith chemical reservoir transfer, as well as CO 2 , O 3 , and H 2 O isotopic interactions at the time of formation of each specific carbonate. The carbon isotopes preserved in the Ca-rich carbonate phase indicate that the Noachian atmosphere of Mars was substantially depleted in 13 C compared with the modern atmosphere.Martian meteorite | oxygen isotope anomaly | aqueous interaction | carbon isotope | photochemistry G eological evidence suggests that early Mars was sufficiently warm for liquid water to flow on the surface for at least brief periods, if not longer (1). Identifying the nature and duration of warmer conditions on the Martian surface is one of the key pieces of information for understanding atmosphere-hydrosphere-geosphere interactions, the evolution of the atmosphere, and potential past habitability. A better understanding of the evolution of the Martian atmosphere and, in particular, the behavior of its primary component, CO 2 , provides a means for characterizing the nature of the ancient Martian environment. The amount of CO 2 present in the atmosphere should provide critical insight into the characteristics of the Martian climate, with a denser atmosphere being more likely to be able to support prolonged warmer temperatures (2, 3).The Martian meteorite ALH 84001 is a critical source for understanding the history of the Martian atmosphere, as it is the oldest known rock (crystallographic age ∼4.09 ± 0.03 Ga) (4), and its carbonate fractions (<1% wt/wt) are considered to have preserved the carbon isotope signature of the ancient atmosphere ∼3.9 Ga ago (5). These carbonates are chemically (Mg-, Ca-, and FeMn rich) and isotopically (δ 13 C VPDB = 27-64, where VPDB stands for Vienna Pee Dee Belemnite, and δ 18 O SMOW = −10-27‰, where SMOW stands for Standard Mean Ocean Water) heterogeneous on micrometer scales; carbon and oxygen isotopes show a covariant relationship that is correlated with Mg content of the mineral (6-8). The exact process responsible for their formation is not clear, although low-temperature aqueous precipitation, biogenic production, evaporation, and high-temperature reactions are all candidate processes (9-13). Decoding the fingerprints of various oxygen-carry...

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Ozone photolysis: Strong isotopologue/isotopomer selectivity in the stratosphere

et al. 2014

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We calculated the photolysis rate coefficients of five ozone isotopologues/isotopomers as functions of altitude up to 80 km using recent ab initio absorption cross sections and an averaged actinic flux. Three of the five ozone isotopologues/isotopomers are symmetric, with a single isotopic dissociation channel, and two are asymmetric with two isotopic dissociation channels. The specific contributions of the Chappuis, Huggins, and Hartley bands to the photolysis rates and enrichments have been determined as a function of altitude. The Chappuis and Hartley bands have a dominant contribution to the photolysis rates, respectively at low and high altitudes, but these two bands are characterized by small fractionations. In contrast, the Huggins band has a minor contribution to the overall photolysis rate at any altitude, but it generates most of the strong fractionation which peaks around 35 km. The photolysis fractionations are "mass dependent" in contrast with those due to the ozone formation process which are "non-mass dependent." The altitude dependences of our photolysis fractionations are in qualitative agreement with those of Liang et al. (2006)

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Investigations of the photochemical isotope equilibrium between O<sub>2</sub>, CO<sub>2</sub> and O<sub>3</sub>

Cited by 25 publications

References 31 publications

Large and unexpected enrichment in stratospheric ¹⁶ O ¹³ C ¹⁸ O and its meridional variation

Large and unexpected enrichment in stratospheric ¹⁶ O ¹³ C ¹⁸ O and its meridional variation

Carbonate formation events in ALH 84001 trace the evolution of the Martian atmosphere

Ozone photolysis: Strong isotopologue/isotopomer selectivity in the stratosphere

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Investigations of the photochemical isotope equilibrium between O&lt;sub&gt;2&lt;/sub&gt;, CO&lt;sub&gt;2&lt;/sub&gt; and O&lt;sub&gt;3&lt;/sub&gt;

Cited by 25 publications

References 31 publications

Large and unexpected enrichment in stratospheric 16 O 13 C 18 O and its meridional variation

Large and unexpected enrichment in stratospheric 16 O 13 C 18 O and its meridional variation

Carbonate formation events in ALH 84001 trace the evolution of the Martian atmosphere

Ozone photolysis: Strong isotopologue/isotopomer selectivity in the stratosphere

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Investigations of the photochemical isotope equilibrium between O<sub>2</sub>, CO<sub>2</sub> and O<sub>3</sub>

Large and unexpected enrichment in stratospheric ¹⁶ O ¹³ C ¹⁸ O and its meridional variation

Large and unexpected enrichment in stratospheric ¹⁶ O ¹³ C ¹⁸ O and its meridional variation