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30. M. X. Kirby, B. MacFadden, Palaeogeogr. Palaeoclimatol. OISE, EAR, DRL 0966884, Colciencias, and the National Geographic Supplementary Text Palaeoecol. 228, 193–202 (2005). Society. We thank N. Hoyos, D. Villagomez, A. O’Dea, C. Bustamante, Figs. S1 to S3 O. Montenegro, and C. Ojeda. All the data reported in this manuscript Tables S1 to S5 ACKNOWLEDGMENTS are presented in the main paper and in the supplementary materials. References (31–42) Supported by Ecopetrol-ICP “Cronología de la Deformación en las Cuencas Subandinas,” Smithsonian Institution, Uniandes P12. SUPPLEMENTARY MATERIALS 160422.002/001, Autoridad del Canal de Panama (ACP), the Mark www.sciencemag.org/content/348/6231/226/suppl/DC1 12 November 2014; accepted 2 March 2015 Tupper Fellowship, Ricardo Perez S.A.; NSF grant EAR 0824299 and Materials and Methods 10.1126/.aaa2815

EARTH HISTORY The PTB in the Tethys is characterized by two negative d13C excursions interrupted by a short- term positive event (10). There is no consensus as acidification and the to the cause of this “rebound” event and so we instead focus on the broader d13Ctrend.Ourd13C Permo-Triassic mass transect (Fig. 1B) starts in the Changhsingian (Late Permian) with a gradual decreasing trend, interrupted by the first negative shift in d13Cat M. O. Clarkson,1*† S. A. Kasemann,2 R. A. Wood,1 T. M. Lenton,3 S. J. Daines,3 EP1 (at 53 m, ~251.96 Ma) (Figs. 1B and 2). This is S. Richoz,4 F. Ohnemueller,2 A. Meixner,2 S. W. Poulton,5 E. T. Tipper6 followed by the minor positive rebound event (at 54 m, ~251.95 Ma) (Figs. 1B and 2) before the triggered by Siberian Trap volcanism was a possible kill mechanism minima of the second phase of the negative CIE for the Permo-Triassic Boundary mass extinction, but direct evidence for an acidification (58to60m,~251.92Ma)(Figs.1Band2)that event is lacking. We present a high-resolution pH record across this interval, marks the PTB itself. After the CIE minimum, using boron isotope data combined with a quantitative modeling approach. In the latest d13C gradually increases to ~1.8 per mil (‰) and Permian, increased ocean primed the system with a low level of remains relatively stable during the earliest

atmospheric CO and a high ocean buffering capacity. The first phase of extinction on April 10, 2015 2 Triassic and across EP2. was coincident with a slow injection of into the , and ocean Our boron isotope record shows a different pH remained stable. During the second extinction pulse, however, a rapid and large pattern to the carbon isotope excursion. The injection of carbon caused an abrupt acidification event that drove the preferential loss boron isotope ratio (d11B) is persistently low of heavily calcified marine biota. (Fig. 1C) at the start of our record during the late-Changhsingian, with an average of 10.9 T he Permo-Triassic Boundary (PTB) mass (7). A rapid input of carbon is also potentially 0.9‰ (1s). This is in agreement with d11Bvalues extinction, at ~252 million years ago (Ma), recorded in the negative carbon isotope excur- (average of 10.6 T 0.6‰,1s) reported for early- represents the most catastrophic loss of sion (CIE) that characterizes the PTB interval Permian brachiopods (19). Further up the section 10 11 (at ~40 m, ~252.04 Ma) (Fig. 1C), there is a stepped in geological history and played ( , ). The interpretation of these records is, www.sciencemag.org T 12–16 d11 T ‰ a major role in dictating the subsequent however, debated ( ) and is of great impor- increase in Bto15.3 0.8 (propagated evolution of modern (1). The PTB ex- tance to understanding the current threat of uncertainty, 2sf) and by implication an increase tinction event spanned ~60,000 years (2)and anthropogenically driven ocean acidification (11). inoceanpHof~0.4to0.5(Fig.2).d11Bvalues can be resolved into two distinct marine extinc- To test the ocean acidification hypothesis, we then remain relatively stable, scattering around tion pulses (3). The first occurred in the latest have constructed a record of ocean pH 14.7 T 1.0‰ (1s) and implying variations within Permian [Extinction Pulse 1 (EP1)] and was fol- across the PTB using the boron isotope compo- 0.1 to 0.2 pH, into the Early Griesbachian (Early lowed by an interval of temporary recovery be- sition of marine (d11B) (17). We then Triassic) and hence across EP1 and the period of fore the second pulse (EP2), which occurred in used a model (supplementary text) carbon cycle disturbance (Figs. 1 and 2). Downloaded from the earliest Triassic. The direct cause of the mass to explore ocean chemistry and pH After the d13C increase and stabilization (at extinction is widely debated, with a diverse range scenarios that are consistent with our d11Bdata ~85 m, ~251.88 Ma) (Fig. 1), d11B begins to de- of overlapping mechanisms proposed, including and published records of carbon cycle distur- crease rapidly to 8.2 T 1.2‰ (2sf), implying a widespread water column anoxia (4), euxinia (5), bance and environmental conditions. Through sharpdropinpHof~0.6to0.7.Thed11Bmin- global warming (6), and ocean acidification (7). this combined geochemical, geological, and model- imum is coincident with the interval identified Models of PTB ocean acidification suggest that ing approach, we are able to produce an envelope as EP2. This ocean acidification event is short- 11 a massive and rapid release of CO2 from Siberian that encompasses the most realistic range in pH, lived (~10,000 years), and d B values quickly re- Trap volcanism acidified the ocean (7). Indirect which then allows us to resolve three distinct cover toward the more alkaline values evident evidence for acidification comes from the inter- chronological phases of carbon cycle perturba- during EP1 (average of ~14‰). pretation of faunal turnover records (3, 8), poten- tion,eachwithverydifferent environmental con- The initial rise in ocean pH of ~0.4 to 0.5 units tial dissolution surfaces (9), and Ca isotope data sequences for the Late Permian–Early Triassic duringtheLatePermian(Fig.2)suggestsalarge Earth system. increase in carbonate alkalinity (20). We are able 1 School of Geosciences, University of Edinburgh, West Mains We analyzed boron and carbon isotope data to simulate the observed rise in d11B and pH Road, Edinburgh EH9 3FE, UK. 2Faculty of Geosciences and MARUM–Center for Marine Environmental Sciences, from two complementary transects in a shallow through different model combinations of in- University of Bremen, 28334 Bremen, Germany. 3College marine, open-water carbonate succession from the creasing weathering, increased pyrite dep- of Life and Environmental Sciences, University of Exeter, United Arab Emirates (U.A.E.), where deposi- osition (21), an increase in carbonate weathering, Laver Building, North Parks Road, Exeter EX4 4QE, UK. 4 tional facies and stable carbon isotope ratio and a decrease in shallow marine carbonate dep- Institute of Earth Sciences, NAWI Graz, University of Graz, 13 Heinrichstraße 26, 8010 Graz, Austria. 5School of Earth and (d C) are well constrained (18). During the ositional area (supplementary text). Both sili- Environment, University of Leeds, Leeds LS2 9JT, UK. PTB interval, the U.A.E. formed an expansive cate weathering and pyrite deposition result in a 6Department of Earth Sciences, University of Cambridge, carbonate platform that remained connected large drop in partial pressure of CO2 (PCO2)(and Downing Street, Cambridge CB2 3EQ, UK. to the central Neo-Tethyan Ocean (Fig. 1A) (18). ) for a given increase in pH and *Corresponding author. E-mail: [email protected] d13 W †Present address: Department of Chemistry, University of Otago, Conodont stratigraphy and the distinct Ccurve saturation state ( ).Thereisnoevidencefora Union Street, Dunedin, 9016, Post Office Box 56, New Zealand. are used to constrain the age model (17). large drop in PCO2, and independent proxy data

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Fig. 1. Site locality and high-resolution Bioclastic pack-grainstone Transect carbon and boron Calcisphere grainstone WSA SHA1 isotope data. (A) Laminated to massive dolomudstone PALEOTETHYS Paleogeographic Bioturbated mud- to packstone N EO reconstruction for the -T E T

Unidentified (estimated texture) A H Late Permian showing E Y

S G

the studied section N Gastropods A

Wadi Bih, in the P Calcareous algae Musandam Mountains Bivalves of U.A.E., that formed Thinsection Outcrop an extensive carbon- ate platform in the 100 Neo-Tethyan Ocean. mid-Bih breccia [Modified from (35).] 13 90 (B) Shallow water d C I.isarcica EP2 record (18). (C) Boron 85 isotope (d11B) record (propagated uncer- tainty given as 2sƒ ) 80 and average Early Per- mian brachiopod value 75 ?

n 19 Griesbachian ( = 5 samples) ( ). Early Triassic Lithology, biota, and 70 H . parvus H . transect key are Thrombolite provided in (A). Only 65 Hindeodus parvus has been found so far in 60 this section (18), and PTB the conodont zones praeparvus 55

with dashed lines are H. EP1 identified from the 13 d C record and 50 C.yini regional stratigraphy (36–38). 45

40

35

30

25 Late Permian Changhsingian

20 changxingensis C .

15

10

Average Early-Permian 5 Brachiopod

0 (m) WP G MFRB Fossils 012345 6 8 1012141618 11 Zone δ13 δ B (‰)

Conodont C (‰) indicate only a minor temperature decrease of A decrease in carbonate sedimentation is con- -level fall also exposed carbonates to weath- a few degrees celsius during the Changhsingian sistent with the decrease in depositional shelf ering (23), which would have further augmented (22), suggesting that these mechanisms alone can- area that occurred because of the second-order thealkalinityinflux.ThepHincreaseeventsup- not explain the pH increase (fig. S5). Conversely, regression of the Late Permian (23). With the ports the CO2Lo initialization scenario [CO2 ~3 11 an increase in carbonate input or a reduction in added expansion of anoxia into shelf environ- present atmospheric levels (PAL), pH ~8, d BSW rates of carbonate deposition both result in in- ments (24), this would effectively create both ~34‰] (supplementary text) because the simu- creases in W, with a greater impact on pH per bottom-up and top-down pressures to reduce lated CO2 and temperature decrease is much re- unit decrease in PCO2 and temperature (fig. S6). the area of potential carbonate sedimentation. duced and therefore is more consistent with

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13 18 8.4 pH and stable d C values (Fig. 2) through a large and rapid carbon release of 2 × 1018 mol C over 16 8.2 10,000years(fig.S8).Thisisundoubtedlyamas- 14 8 sive injection of 24,000 PgC at a rapid rate of (‰) − 4 2.4 PgC/year, but it is physically plausible given

12 total 7.8 existing estimates of the volume of carbonate pH B(OH) 10 host sediments subject to contact metamorphism 11 7.6 δ and postulated mechanisms of carbon release 8 7.4 (supplementary text). This second rapid carbon release produces a sharp rise in PCO to ~20 PAL 6 7.2 2 and warming of ~15°C, which is consistent with 5 30 the observation of peak after EP1 (22). Initialization of the carbon cycle model un- 4 25 11 der CO2Hi cannot generate the magnitude of d B 3 20 drop (Fig. 2A) because the nonlinear relation be-

(‰) tween pH and d11B fractionation sets a lower limit PAL

2 2 15 11 carb of d Bat~10‰ in this case (fig. S3). Thus, low C pCO 13 1 10 initial CO2 of ~3 PAL in the Late Permian (CO2Lo) δ Data CO2Lo is more consistent with our data. 0 5 CO2Hi An acidification event of ~10,000 years is −1 0 consistent with the modeled time scale required to replenish the ocean with alkalinity, as car- bonate deposition is reduced and weathering 251.85 251.95 252.05 252.15 251.85 251.95 252.05 252.15 is increased under higher PCO2 and global tem- Age (My) Age (My) peratures. Increased silicate weathering rates drive further CO2 drawdown, resulting in stabi- Fig. 2. Model results of carbon cycle parameters for high- and low-CO2 end-member scenarios. lization (Fig. 2D). High global temperature (6) (A)Model-reproducedd11Bversusdata.(B) Modeled d13C versus data. (C) Modeled pH envelope in- and increased silicate weathering are consistent 11 87 86 corporating uncertainty of seawater B isotope composition (d BSW) and dynamic temperatures. with a sudden increase in both Sr/ Sr (34)and (D) Calculated atmospheric CO2. sedimentation rates (29) in the Griesbachian. The PTB was a time of extreme environmental independent proxy data (22), as compared with silicate weathering, creating an additional counter- change, and our combined data and modeling 11 CO2Hi (CO2 ~10 PAL, pH ~7.5, d BSW ~36.8‰) balancing alkalinity flux, which is consistent with approach falsifies several of the mechanisms cur- (Fig. 2D). independent proxy data (6). The alkalinity source rently proposed. Although the coincident stresses 13 Before EP1, d Ccarb values began to decrease may have been further increased through soil loss of anoxia, increasing temperature, and before reaching the minimum of the globally (29), the emplacement of easily weathered Siberian restructuring were important during this interval, recognized negative CIE at the PTB (Fig. 1). At Trap basalt, or the impact of rain (30), which the d11B record strongly suggests that widespread this time, both d11B and ocean pH remained would have increased weathering efficiency. ocean acidification was not a factor in the first 11 stable. Hypotheses to explain the negative CIE The negative d Bcarb excursion at 251.88 Ma phase of the mass extinction but did drive the require the input of isotopically light carbon, represents a calculated pH decrease of up to second pulse. The carbon release required to such as from volcanism (14, 25), with the assimi- 0.7 pH. This pH decrease coincides with the drive the observed acidification event must have lation of very light organic carbon from the sur- second pulse of the extinction (Fig. 1), which pref- occurred at a rate comparable with the current rounding host rock (26), destabilization erentially affected the heavily calcifying, phys- anthropogenic perturbation but exceeds it in (27), collapse of the (15), and/or iologically unbuffered, and sessile organisms (3). expected magnitude. Specifically, the required a decrease in the burial of terrestrial carbon (16). This was also accompanied by the temporary loss model perturbation of 24,000 PgC exceeds the We can simulate the observed drop in d13C, while of abiotic and microbial carbonates throughout ~5000 PgC of conventional fossil fuels and is remaining within the uncertainty of the d11B the Tethys (31, 32), suggesting a coeval decrease at the upper end of the range of estimates of data (Fig. 2), by combining a cessation of ter- in W. To overwhelm the buffering capacity of the unconventional fossil fuels (such as methane restrial carbon burial with a relatively slow ocean and decrease pH in this way requires a hydrates). We show that such a rapid and large (50,000 years) carbon injection from any of the second, more abrupt injection of carbon into the release of carbon is critical to causing the com- above sources (fig. S8). A small source of methane atmosphere, yet remarkably, the acidification bined synchronous decrease in both pH and satu- (3.2 × 1017 mol C with d13C=–50‰) gives the least event occurs after the decline in d13C, when d13C ration state that defines an ocean acidification change in d11B and pH, whereas either a larger hasreboundedsomewhatandisessentiallystable event (11). source of organic carbon (~6.5 × 1017 mol C with (Fig. 1). d13C=–25‰)oramixtureofmantleandlighter Unlike the first carbon injection, the lack of REFERENCES AND NOTES carbon sources (~1.3 × 1018 mol C with d13C= change in d13C at this time rules out very 13C- 1. D. H. Erwin, 367, 231–236 (1994). – ‰ 2. S. D. Burgess, S. Bowring, S. Z. Shen, Proc.Natl.Acad.Sci.U.S.A. 12.5 ) are still within the measured uncer- depleted carbon sources because no counter- – d11 13 111,3316 3321 (2014). tainty in B. balancing strongly C-enriched source exists. 3. H. J. Song, P. B. Wignall, J. A. Tong, Y. Hongfu, Nat. 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11. B. Hönisch et al., Science 335, 1058–1063 (2012). COMETARY FORMATION 12. C. L. Blättler, H. C. Jenkyns, L. M. Reynard, G. M. Henderson, Earth Planet. Sci. Lett. 309,77–88 (2011). 13. P. B. Wignall, S. Kershaw, P. Y. Collin, S. Crasquin-Soleau, Geol. Soc. Am. Bull. 121, 954–956 (2009). Molecular nitrogen in comet 14. R. A. Berner, Proc. Natl. Acad. Sci. U.S.A. 99, 4172–4177 (2002). 15. M. R. Rampino, K. Caldeira, Terra Nova 17, 554–559 67P/Churyumov-Gerasimenko indicates (2005). 16. W. S. Broecker, S. Peacock, Global Biogeochem. Cycles 13, 1167–1172 (1999). a low formation temperature 17. Materials and methods are available on Science Online 18. M. O. Clarkson et al., Gondwana Res. 24, 233–242 (2013). 19. M. M. Joachimski, L. Simon, R. van Geldern, C. Lecuyer, M. Rubin,1* K. Altwegg,1,2 H. Balsiger,1 A. Bar-Nun,3 J.-J. Berthelier,4 A. Bieler,1,5 Geochim. Cosmochim. Acta 69, 4035–4044 (2005). P. Bochsler,1 C. Briois,6 U. Calmonte,1 M. Combi,5 J. De Keyser,7 F. Dhooghe,7 20. The alternative way to drive an increase in pH would be 1† 8 9 1 5 5 through a removal of carbon; however, this would be evident in P. Eberhardt, B. Fiethe, S. A. Fuselier, S. Gasc, T. I. Gombosi, K. C. Hansen, 1,9 1 1 10 2 10 11 the d13C record, so we can rule it out. M. Hässig, A. Jäckel, E. Kopp, A. Korth, L. Le Roy, U. Mall, B. Marty, 21. Bacterial sulfate reduction (BSR) is a net source of alkalinity if O. Mousis,12 T. Owen,13 H. Rème,14,15 T. Sémon,1 C.-Y. Tzou,1 J. H. Waite,9 P. Wurz1 the generated H2S is buried as pyrite. Pyrite deposition is seen widely in certain settings during the Late Permian to PTB. Further information is provided in the supplementary Molecular nitrogen (N2) is thought to have been the most abundant form of nitrogen in materials. the protosolar nebula. It is the main N-bearing in the of Pluto 22. M. M. Joachimski et al., Geology 40, 195–198 (2012). and Triton and probably the main nitrogen reservoir from which the giant planets 23. H. Yin et al., Earth Sci. Rev. 137,19–33 (2014). 24. P. B. Wignall, R. J. Twitchett, in Catastrophic Events and Mass formed. Yet in comets, often considered the most primitive bodies in the solar system, : Impacts and Beyond, C. Koeberl, K. G. MacLeod, N2 has not been detected. Here we report the direct in situ measurement of N2 in the Eds. (Geological Society of America, Boulder, CO, 2002), Jupiter family comet 67P/Churyumov-Gerasimenko, made by the Rosetta Orbiter pp. 395–413. Spectrometer for Ion and Neutral Analysis mass spectrometer aboard the Rosetta – 25. C. Korte et al., J. Asian Earth Sci. 37, 293 311 (2010). + −3 s 26. H. Svensen et al., Earth Planet. Sci. Lett. 277, 490–500 spacecraft. A N2/CO ratio of (5.70 − 0.66) × 10 (2 standard deviation of the (2009). sampled mean) corresponds to depletion by a factor of ~25.4 +− 8.9 as compared to 27. E. S. Krull, G. J. Retallack, Geol. Soc. Am. Bull. 112, the protosolar value. This depletion suggests that cometary grains formed at 1459–1472 (2000). low-temperature conditions below ~30 kelvin. 28. A. D. Woods, Earth Sci. Rev. 137,6–18 (2013). 29. T. J. Algeo, Z. Q. Chen, M. L. Fraiser, R. J. Twitchett, – Palaeogeogr. Palaeoclimatol. Palaeoecol. 308,1 11 (2011). hermochemical models of the protosolar and surface deposits of N2 ice (3, 4). This mol- 30. B. A. Black, J. F. Lamarque, C. A. Shields, L. T. Elkins-Tanton, nebula (PSN) suggest that molecular nitro- ecule has never been firmly detected in comets; J. T. Kiehl, Geology 42,67–70 (2014). 31. A. Baud, S. Richoz, S. Pruss, Global Planet. Change 55, gen (N2) was the principal nitrogen species however, CN, HCN, NH, NH2,andNH3 among 81–89 (2007). during the disk phase (1) and that the ni- others have been observed spectroscopically (5, 6). – T 32. S. Richoz et al., J. Asian Earth Sci. 39, 236 253 (2010). trogen present in the giant planets was The abundance of N2 in comets is therefore a 33. B. A. Black, L. T. Elkins-Tanton, M. C. Rowe, I. U. Peate, accreted in this form (2). Moreover, Pluto and key to understanding the conditions in which – Earth Planet. Sci. Lett. 317, 363 373 (2012). Triton, which are both expected to have formed they formed. 34. C. Korte et al., Int. J. Earth Sci. 93, 565–581 (2004). 35. G. M. Stampfli, G. D. Borel, Earth Planet. Sci. Lett. 196,17–33 in the same region of the PSN as Jupiter family Condensation or trapping of N2 in ice occurs (2002). comets (JFCs), have N2-dominated atmospheres at similar thermodynamic conditions as those 36. S. Z. Shen et al., Earth Planet. Sci. Lett. 375, 156–165 needed for CO in the PSN (7, 8). This requires (2013). 1Physikalisches Institut, University of Bern, Sidlerstrasse 5, very low PSN temperatures and implies that 37. B. Koehrer et al., GeoArabia 15,91–156 (2010). 2 CH-3012 Bern, Switzerland. Center for Space and the detection of N in comets and its abundance 38. F. Maurer, R. Martini, R. Rettori, H. Hillgartner, S. Cirilli, Habitability, University of Bern, Sidlerstrasse. 5, CH-3012 2 GeoArabia 14, 125–158 (2009). Bern, Switzerland. 3Department of Geoscience, Tel-Aviv ratio with respect to CO would put strong con- University, Ramat-Aviv, Tel-Aviv, Israel. 4Laboratoire straints on comet formation conditions (7, 8). ACKNOWLEDGMENTS Atmosphères, Milieux, Observations Spatiales (LATMOS)/ Ground-based spectroscopic observations of M.O.C. acknowledges funding from the Edinburgh University Institute Pierre Simon Laplace–CNRS-UPMC-UVSQ, 4 Avenue + ’ 5 the N2 band in the near ultraviolet are very Principal s Career Development Scholarship, the International de Neptune F-94100, Saint-Maur, France. Department of + Centre for Carbonate Reservoirs, and The Marsden Fund Atmospheric, Oceanic and Space Sciences, University of difficult because of the presence of telluric N2 (U001314). R.A.W., T.M.L., and S.W.P. acknowledge support Michigan, 2455 Hayward, Ann Arbor, MI 48109, USA. and other cometary emission lines. Searches from the Natural Environment Research Council through the 6Laboratoire de Physique et Chimie de l'Environnement et de conducted with high-resolution spectra of com- “ ” – Co-evolution of Life and the Planet scheme (NE/I005978). T.M.L. l'Espace (LPC2E), UMR 6115 CNRS Université d'Orléans, ets 122P/de Vico, C/1995 O1 (Hale-Bopp), and and S.J.D. were supported by the Leverhulme Trust (RPG-2013-106). Orléans, France. 7Belgian Institute for Space Aeronomy, S.A.K. and A.M. acknowledge support from the German Research Belgisch Instituut voor Ruimte-Aeronomie–Institut 153P/2002 C1 (Ikeya-Zhang) have been unsuc- −5 −4 Foundation (Deutsche Forschungsgemeinschaft) Major Research d’Aéronomie Spatiale de Belgique (BIRA-IASB), Ringlaan 3, cessful and yielded upper limits of 10 to 10 Instrumentation Program INST 144/307-1. This is a contribution to B-1180 Brussels, Belgium. 8Institute of Computer and + + + for the N2 /CO ratio (9, 10). Only one N2 de- IGCP 572, with S.R. sponsored for fieldwork by the Austrian National Network Engineering, Technische Universität Braunschweig, tection in C/2002 VQ94 (LINEAR) from ground- Committee (Austrian Academy of Sciences) for the International Hans-Sommer-Straße 66, D-38106 Braunschweig, Germany. Geoscience Programme (IGCP). We are grateful to R. Newton 9Department of Space Science, Southwest Research based observations is convincing, because the and A. Thomas for helpful discussions, L. Krystyn for field assistance, Institute, 6220 Culebra Road, San Antonio, TX 78228, USA. comet was at sufficient distance from the Sun F. Maurer for discussions on stratigraphy and providing 10Max-Planck-Institut für Sonnensystemforschung, Justus- to prevent terrestrial twilight N + contamina- 11 2 photomicrographs, and B. Mills for assisting with model studies. Data von-Liebig-Weg 3, 37077 Göttingen, Germany. Centre de tion (11). The in situ measurements made by are available online in the supplementary materials and at www. Recherches Pétrographiques et Géochimiques (CRPG)– pangaea.de. CNRS, Université de Lorraine, 15 rue Notre Dame des Giotto in 1P/Halley were inconclusive, because Pauvres, Bôite Postale 20, 54501 Vandoeuvre lès Nancy, the resolution of the mass spectrometers aboard 12 SUPPLEMENTARY MATERIALS France. Aix Marseille Université, CNRS, Laboratoire the spacecraft (12) was insufficient to separate d'Astrophysique de Marseille UMR 7326, 13388, Marseille, www.sciencemag.org/content/348/6231/229/suppl/DC1 thenearlyidenticalmassesofN and CO during France. 13Institute for Astronomy, University of Hawaii, 2 Materials and Methods Honolulu, HI 96822, USA. 14Université de Toulouse; UPS- the1P/Halleyencounter,andonlyanupperlimit Supplementary Text OMP; Institut de Recherche en Astrophysique et Planétologie could be derived for the relative production Figs. S1 to S9 (IRAP), Toulouse, France. 15CNRS; IRAP; 9 Avenue du Q Q ≤ 13 Tables S1 to S10 rates [ (N2)/ (CO) 0.1] ( ). Colonel Roche, Boîte Postale 44346, F-31028 Toulouse References (39–98) Here we report the direct in situ measurement Cedex 4, France. 8 October 2014; accepted 4 March 2015 *Corresponding author. E-mail: [email protected] of the N2/CO ratio by the Rosetta Orbiter Spec- 10.1126/science.aaa0193 †Deceased. trometer for Ion and Neutral Analysis (ROSINA)

232 10 APRIL 2015 • VOL 348 ISSUE 6231 sciencemag.org SCIENCE Ocean acidification and the Permo-Triassic mass extinction M. O. Clarkson et al. Science 348, 229 (2015); DOI: 10.1126/science.aaa0193

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