The Action of Water

Brearley, Adrian J.

doi:10.2307/j.ctv1v7zdmm.35

Cited by 317 publications

(167 citation statements)

References 104 publications

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“…Consistent with the mineralogy of aqueously altered chondrites (Brearley & Jones, 1998;Brearley, 2006), the relatively low density of Enceladus' rocky core (Iess et al, 2014), and experimental (Sekine et al, 2014) and theoretical (Zolotov, 2007)…”

Section: Serpentinization Of Chondritic Rocksupporting

confidence: 53%

“…Thus, serpentinizing systems on Earth, such as the Semail ophiolite in Oman and the Lost City hydrothermal field in the mid-Atlantic Ocean, can be regarded as reasonable geochemical and perhaps biological analogues of the water-rock (i.e., ocean-core) system on Enceladus (see Section 5.2). This discussion echoes the emerging theme of serpentinization as the most important alteration reaction in the Solar System (Brearley, 2006;Schulte et al, 2006;Ehlmann et al, 2010), which suggests that subsurface oceans on other worlds in the outer Solar System (Hussmann et al, 2006;Castillo-Rogez & McCord, 2010;Robuchon & Nimmo, 2011;Hammond et al, 2013) would also be alkaline solutions (Zolotov, 2012).…”

Section: Serpentinization Of Chondritic Rockmentioning

confidence: 66%

“…An important consequence of serpentinization is the simultaneous generation of H2 by aqueous oxidation of reduced iron-bearing minerals (Neal & Stanger, 1983;Sleep et al, 2004;Oze & Sharma, 2007;McCollom & Bach, 2009;Klein et al, 2013;Mayhew et al, 2013). The presence of ferric (Fe +3 ) phases (e.g., magnetite, maghemite, cronstedtite) in aqueously altered chondrites (Brearley, 2006) demonstrates that this process can also occur in chondritic systems (Rosenberg et al, 2001;Alexander et al, 2010). The likely occurrence of serpentinization on Enceladus thus implies that H2 has been produced inside Enceladus, where the dominant source of H2 is suggested to be the oxidation of accreted metallic iron (which is abundant in primitive bodies and also unstable in the presence of liquid water at sub-kbar pressures; Brearley & Jones, 1998;Zolensky et al, 2006;Glein et al, 2008) 3Fe(Kamacite) + 4H2O(l) → Fe3O4(Magnetite) + 4H2(aq).…”

Section: Hydrogen Generation From Iron Oxidationmentioning

confidence: 99%

“…The occurrence of serpentinization on Enceladus (see Section 4.1) therefore suggests that the geochemical environment on this icy world would be conducive to abiogenesis. Yet, serpentinization does not necessarily lead to life, given that carbonaceous chondrites do not appear to contain extraterrestrial organisms, despite the occurrence of serpentinization on many meteorite parent bodies (i.e., asteroids; Brearley, 2006). A simple hypothesis for the non-emergence of life in meteorites is that liquid water did not exist long enough (Abramov & Mojzsis, 2011).…”

Section: Serpentinization and The Origin Of Lifementioning

confidence: 99%

“…This ocean is believed to be the source of gases, organics, salts, and ices in Enceladus' cryovolcanic plume (Spencer & Nimmo, 2013), although clathrate hydrates could also play a role (Kieffer et al, 2006;Fortes, 2007;Bouquet et al, 2014). Understanding the geochemistry of the ocean is critical for advancing our understanding of the origin and evolution of Enceladus (Zolotov, 2007;Matson et al, 2007;Glein et al, 2008;Zolotov et al, 2011); for gaining insights into geochemical processes on other icy bodies in the outer Solar System (Shock & McKinnon, 1993;Kargel et al, 2000;Glein et al, 2009); for comparing aqueous geochemistry on Enceladus to that on the modern and early Earth (Holland, 1984;Sverjensky & Lee, 2010;Pope et al, 2012), Mars (Grotzinger et al, 2014), and asteroids (Zolensky et al, 1999;Brearley, 2006;Zolotov, 2014); for assessing the biological potential of Enceladus (McKay et al, 2008;Parkinson et al, 2008); and for planning future missions to Enceladus (Sotin et al, 2011;Tsou et al, 2012) and other worlds where ocean water may be erupting into space (Pappalardo et al, 2013;Küppers et al, 2014;Roth et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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The pH of Enceladus’ ocean

Glein

Baross

Waite

2015

Geochimica et Cosmochimica Acta

221

188

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Saturn's icy moon, Enceladus, is a geologically active waterworld. The prevailing paradigm is that there is a subsurface ocean that erupts to the surface, which leads to the formation of a plume of vapor and ice above the south pole. The chemical composition of the ocean is just beginning to be understood, but is of profound geochemical and astrobiological interest. Here, we address the most fundamental question about the ocean's chemistry by determining its pH, using a thermodynamic model of carbonate speciation. Observational data from the Cassini spacecraft are used to obtain a chemical model of ocean water on Enceladus, the first such model for another planet/moon that is based on empirical evidence. The abundance of CO2 in the plume gas, as measured by the Ion and Neutral Mass Spectrometer onboard Cassini, is essential to elucidating the pH. The geochemical model indicates that Enceladus' ocean is a Na-Cl-CO3 solution with an alkaline pH of ~11-12. The dominance of aqueous NaCl is a geochemical feature that Enceladus' ocean shares with terrestrial seawater, but the ubiquity of dissolved Na2CO3 suggests that soda lakes are more analogous to the Enceladus ocean. The high pH implies that the hydroxide ion should be relatively abundant, while divalent metals should be present at low concentrations in ocean water owing to buffering by clays and carbonates on the ocean floor. In addition, carboxyl groups in dissolved organic species (such as possible biomolecules) would be negatively charged, whereas amino groups would exist predominately in the neutral form. Knowledge of the pH dramatically improves our understanding of geochemical processes in Enceladus' ocean. In particular, the high pH is interpreted to be a key consequence of serpentinization of chondritic rock, as predicted by prior geochemical reaction path models, although degassing of CO2 from the ocean may also play a 3 role depending on the efficiency of mixing processes in the ocean. Serpentinization inevitably leads to the generation of H2, a geochemical fuel that can support both abiotic and biological synthesis of organic molecules such as those that have been detected in Enceladus' plume.Serpentinization and H2 generation should have occurred on Enceladus, like on the parent bodies of aqueously altered meteorites; but it is unknown whether these critical processes are still taking place, or if Enceladus' rocky core has been completely altered by past hydrothermal activity. The presence of native H2 in the plume would provide strong evidence for contemporary aqueous alteration. The high pH also suggests that the delivery of oxidants from the surface to the ocean has been sporadic, and the rocky core did not experience partial melting and igneous differentiation. On the other hand, the deduced pH is completely compatible with life as we know it; indeed, life on Earth may have begun under similar conditions, and terrestrial serpentinites support thriving microbial communities that are centered on H2 that is provided by water-rock reactions. T...

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Section: Serpentinization Of Chondritic Rocksupporting

confidence: 53%

Section: Serpentinization Of Chondritic Rockmentioning

confidence: 66%

Section: Hydrogen Generation From Iron Oxidationmentioning

confidence: 99%

Section: Serpentinization and The Origin Of Lifementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The pH of Enceladus’ ocean

Glein

Baross

Waite

2015

Geochimica et Cosmochimica Acta

221

188

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Shock wave synthesis of amino acids from solutions of ammonium formate and ammonium bicarbonate

Suzuki

Furukawa

Kobayashi

et al. 2015

Geochem Geophys Geosyst

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The emergence of life's building blocks, such as amino acids and nucleobases, on the prebiotic Earth was a critical step for the beginning of life. Reduced species with low mass, such as ammonia, amines, or carboxylic acids, are potential precursors for these building blocks of life. These precursors may have been provided to the prebiotic ocean by carbonaceous chondrites and chemical reactions related to meteorite impacts on the early Earth. The impact of extraterrestrial objects on Earth occurred more frequently during this period than at present. Such impacts generated shock waves in the ocean, which have the potential to progress chemical reactions to form the building blocks of life from reduced species. To simulate shock-induced reactions in the prebiotic ocean, we conducted shock-recovery experiments on ammonium bicarbonate solution and ammonium formate solution at impact velocities ranging from 0.51 to 0.92 km/s. In the products from the ammonium formate solution, several amino acids (glycine, alanine, ß-alanine, and sarcosine) and aliphatic amines (methylamine, ethylamine, propylamine, and butylamine) were detected, although yields were less than 0.1 mol % of the formic acid reactant. From the ammonium bicarbonate solution, smaller amounts of glycine, methylamine, ethylamine, and propylamine were formed. The impact velocities used in this study represent minimum cases because natural meteorite impacts typically have higher velocities and longer durations. Our results therefore suggest that shock waves could have been involved in forming life's building blocks in the ocean of prebiotic Earth, and potentially in aquifers of other planets, satellites, and asteroids.

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Multiple carriers of Q noble gases in primitive meteorites

Marrocchi

Avice

Estrade

2015

Geophysical Research Letters

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The main carrier of primordial heavy noble gases in chondrites is thought to be an organic phase, known as phase Q, whose precise characterization has resisted decades of investigation. Indirect techniques have revealed that phase Q might be composed of two subphases, one of them associated with sulfide. Here we provide experimental evidence that noble gases trapped within meteoritic sulfides present chemically and thermally driven behavior patterns that are similar to Q gases. We therefore suggest that phase Q is likely composed of two subcomponents: carbonaceous phases and sulfides. In situ decay of iodine at concentration levels consistent with those reported for meteoritic sulfides can reproduce the 129Xe excess observed for Q gases relative to fractionated solar wind. We suggest that the Q‐bearing sulfides formed at high temperature and could have recorded the conditions that prevailed in the chondrule‐forming region(s).

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The Action of Water

Cited by 317 publications

References 104 publications

The pH of Enceladus’ ocean

The pH of Enceladus’ ocean

Shock wave synthesis of amino acids from solutions of ammonium formate and ammonium bicarbonate

Multiple carriers of Q noble gases in primitive meteorites

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