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Kloprogge JT(T, Hartman H. Clays and the Origin of Life: The Experiments. Life (Basel) 2022; 12:life12020259. [PMID: 35207546 PMCID: PMC8880559 DOI: 10.3390/life12020259] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/08/2022] [Accepted: 02/01/2022] [Indexed: 12/15/2022] Open
Abstract
There are three groups of scientists dominating the search for the origin of life: the organic chemists (the Soup), the molecular biologists (RNA world), and the inorganic chemists (metabolism and transient-state metal ions), all of which have experimental adjuncts. It is time for Clays and the Origin of Life to have its experimental adjunct. The clay data coming from Mars and carbonaceous chondrites have necessitated a review of the role that clays played in the origin of life on Earth. The data from Mars have suggested that Fe-clays such as nontronite, ferrous saponites, and several other clays were formed on early Mars when it had sufficient water. This raised the question of the possible role that these clays may have played in the origin of life on Mars. This has put clays front and center in the studies on the origin of life not only on Mars but also here on Earth. One of the major questions is: What was the catalytic role of Fe-clays in the origin and development of metabolism here on Earth? First, there is the recent finding of a chiral amino acid (isovaline) that formed on the surface of a clay mineral on several carbonaceous chondrites. This points to the formation of amino acids on the surface of clay minerals on carbonaceous chondrites from simpler molecules, e.g., CO2, NH3, and HCN. Additionally, there is the catalytic role of small organic molecules, such as dicarboxylic acids and amino acids found on carbonaceous chondrites, in the formation of Fe-clays themselves. Amino acids and nucleotides adsorb on clay surfaces on Earth and subsequently polymerize. All of these observations and more must be subjected to strict experimental analysis. This review provides an overview of what has happened and is now happening in the experimental clay world related to the origin of life. The emphasis is on smectite-group clay minerals, such as montmorillonite and nontronite.
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Affiliation(s)
- Jacob Teunis (Theo) Kloprogge
- School of Earth and Environmental Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
- Department of Chemistry, College of Arts and Sciences, University of the Philippines Visayas, Miagao 5023, Philippines
- Correspondence: (J.T.K.); (H.H.)
| | - Hyman Hartman
- Department of Earth Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
- Correspondence: (J.T.K.); (H.H.)
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González Henao S, Karanauskas V, Drummond SM, Dewitt LR, Maloney CM, Mulu C, Weber JM, Barge LM, Videau P, Gaylor MO. Planetary Minerals Catalyze Conversion of a Polycyclic Aromatic Hydrocarbon to a Prebiotic Quinone: Implications for Origins of Life. ASTROBIOLOGY 2022; 22:197-209. [PMID: 35100015 DOI: 10.1089/ast.2021.0024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in astrochemical environments and are disbursed into planetary environments via meteorites and extraterrestrial infall where they may interact with mineral phases to produce quinones important for origins of life. In this study, we assessed the potential of the phyllosilicates montmorillonite (MONT) and kaolinite (KAO), and the enhanced Mojave Mars Simulant (MMS) to convert the PAH anthracene (ANTH) to the biologically important 9,10-anthraquinone (ANTHQ). All studied mineral substrates mediate conversion over the temperature range assessed (25-500°C). Apparent rate curves for conversion were sigmoidal for MONT and KAO, but quadratic for MMS. Conversion efficiency maxima for ANTHQ were 3.06% ± 0.42%, 1.15% ± 0.13%, and 0.56% ± 0.039% for MONT, KAO, and MMS, respectively. We hypothesized that differential substrate binding and compound loss account for the apparent conversion kinetics observed. Apparent loss rate curves for ANTH and ANTHQ were exponential for all substrates, suggesting a pathway for wide distribution of both compounds in warmer prebiotic environments. These findings improve upon our previously reported ANTHQ conversion efficiency on MONT and provide support for a plausible scenario in which PAH-mineral interactions could have produced prebiotically relevant quinones in early Earth environments.
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Affiliation(s)
| | | | - Samuel M Drummond
- Department of Chemistry, Dakota State University, Madison, South Dakota, USA
| | - Lillian R Dewitt
- Department of Chemistry, Dakota State University, Madison, South Dakota, USA
| | | | - Christina Mulu
- Department of Chemistry, Dakota State University, Madison, South Dakota, USA
| | - Jessica M Weber
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Laura M Barge
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Patrick Videau
- Department of Biology, Southern Oregon University, Ashland, Oregon, USA
| | - Michael O Gaylor
- Department of Chemistry, Dakota State University, Madison, South Dakota, USA
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3
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Abstract
Ceres is the largest object in the main belt and it is also the most water-rich body in the inner solar system besides the Earth. The discoveries made by the Dawn Mission revealed that the composition of Ceres includes organic material, with a component of carbon globally present and also a high quantity of localized aliphatic organics in specific areas. The inferred mineralogy of Ceres indicates the long-term activity of a large body of liquid water that produced the alteration minerals discovered on its surface, including ammonia-bearing minerals. To explain the presence of ammonium in the phyllosilicates, Ceres must have accreted organic matter, ammonia, water and carbon present in the protoplanetary formation region. It is conceivable that Ceres may have also processed and transformed its own original organic matter that could have been modified by the pervasive hydrothermal alteration. The coexistence of phyllosilicates, magnetite, carbonates, salts, organics and a high carbon content point to rock–water alteration playing an important role in promoting widespread carbon occurrence.
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Singh SK, Bergantini A, Zhu C, Ferrari M, De Sanctis MC, De Angelis S, Kaiser RI. Origin of ammoniated phyllosilicates on dwarf planet Ceres and asteroids. Nat Commun 2021; 12:2690. [PMID: 33976207 PMCID: PMC8113531 DOI: 10.1038/s41467-021-23011-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 03/23/2021] [Indexed: 11/17/2022] Open
Abstract
The surface mineralogy of dwarf planet Ceres is rich in ammonium (NH4+) bearing phyllosilicates. However, the origin and formation mechanisms of ammoniated phyllosilicates on Ceres’s surface are still elusive. Here we report on laboratory simulation experiments under astrophysical conditions mimicking Ceres’ physical and chemical environments with the goal to better understand the source of ammoniated minerals on Ceres’ surface. We observe that thermally driven proton exchange reactions between phyllosilicates and ammonia (NH3) could trigger at low temperature leading to the genesis of ammoniated-minerals. Our study revealed the thermal (300 K) and radiation stability of ammoniated-phyllosilicates over a timescale of at least some 500 million years. The present experimental investigations corroborate the possibility that Ceres formed at a location where ammonia ices on the surface would have been stable. However, the possibility of Ceres’ origin near to its current location by accreting ammonia-rich material cannot be excluded. The authors here propose a chemical reaction that forms ammoniated phyllosilicates on Ceres. This process could trigger at a very low temperature, suggesting Ceres evolution in a region different from its current location.
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Affiliation(s)
- Santosh K Singh
- Department of Chemistry, University of Hawaii, Honolulu, HI, USA.,W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii, Honolulu, HI, USA
| | - Alexandre Bergantini
- Department of Chemistry, University of Hawaii, Honolulu, HI, USA.,W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii, Honolulu, HI, USA.,Federal Center for Technological Education Celso Suckow da Fonseca, Rio de Janeiro, Brazil
| | - Cheng Zhu
- Department of Chemistry, University of Hawaii, Honolulu, HI, USA.,W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii, Honolulu, HI, USA
| | - Marco Ferrari
- Istituto di Astrofisica e Planetologia Spaziali, INAF, Roma, Italy
| | | | | | - Ralf I Kaiser
- Department of Chemistry, University of Hawaii, Honolulu, HI, USA. .,W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii, Honolulu, HI, USA.
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Raponi A, De Sanctis MC, Giacomo Carrozzo F, Ciarniello M, Rousseau B, Ferrari M, Ammannito E, De Angelis S, Vinogradoff V, Castillo-Rogez JC, Tosi F, Frigeri A, Formisano M, Zambon F, Raymond CA, Russell CT. Organic Material on Ceres: Insights from Visible and Infrared Space Observations. Life (Basel) 2020; 11:life11010009. [PMID: 33374247 PMCID: PMC7823631 DOI: 10.3390/life11010009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 12/08/2020] [Accepted: 12/21/2020] [Indexed: 11/17/2022] Open
Abstract
The NASA/Dawn mission has acquired unprecedented measurements of the surface of the dwarf planet Ceres, the composition of which is a mixture of ultra-carbonaceous material, phyllosilicates, carbonates, organics, Fe-oxides, and volatiles as determined by remote sensing instruments including the VIR imaging spectrometer. We performed a refined analysis merging visible and infrared observations of Ceres’ surface for the first time. The overall shape of the combined spectrum suggests another type of silicate not previously considered, and we confirmed a large abundance of carbon material. More importantly, by analyzing the local spectra of the organic-rich region of the Ernutet crater, we identified a reddening in the visible range, strongly correlated to the aliphatic signature at 3.4 µm. Similar reddening was found in the bright material making up Cerealia Facula in the Occator crater. This implies that organic material might be present in the source of the faculae, where brines and organics are mixed in an environment that may be favorable for prebiotic chemistry.
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Affiliation(s)
- Andrea Raponi
- Istituto Nazionale di Astrofisica–Istituto di Astrofisica e Planetologia Spaziali, 00133 Rome, Italy; (M.C.D.S.); (F.G.C.); (M.C.); (B.R.); (M.F.); (S.D.A.); (F.T.); (A.F.); (M.F.); (F.Z.)
- Correspondence:
| | - Maria Cristina De Sanctis
- Istituto Nazionale di Astrofisica–Istituto di Astrofisica e Planetologia Spaziali, 00133 Rome, Italy; (M.C.D.S.); (F.G.C.); (M.C.); (B.R.); (M.F.); (S.D.A.); (F.T.); (A.F.); (M.F.); (F.Z.)
| | - Filippo Giacomo Carrozzo
- Istituto Nazionale di Astrofisica–Istituto di Astrofisica e Planetologia Spaziali, 00133 Rome, Italy; (M.C.D.S.); (F.G.C.); (M.C.); (B.R.); (M.F.); (S.D.A.); (F.T.); (A.F.); (M.F.); (F.Z.)
| | - Mauro Ciarniello
- Istituto Nazionale di Astrofisica–Istituto di Astrofisica e Planetologia Spaziali, 00133 Rome, Italy; (M.C.D.S.); (F.G.C.); (M.C.); (B.R.); (M.F.); (S.D.A.); (F.T.); (A.F.); (M.F.); (F.Z.)
| | - Batiste Rousseau
- Istituto Nazionale di Astrofisica–Istituto di Astrofisica e Planetologia Spaziali, 00133 Rome, Italy; (M.C.D.S.); (F.G.C.); (M.C.); (B.R.); (M.F.); (S.D.A.); (F.T.); (A.F.); (M.F.); (F.Z.)
| | - Marco Ferrari
- Istituto Nazionale di Astrofisica–Istituto di Astrofisica e Planetologia Spaziali, 00133 Rome, Italy; (M.C.D.S.); (F.G.C.); (M.C.); (B.R.); (M.F.); (S.D.A.); (F.T.); (A.F.); (M.F.); (F.Z.)
| | | | - Simone De Angelis
- Istituto Nazionale di Astrofisica–Istituto di Astrofisica e Planetologia Spaziali, 00133 Rome, Italy; (M.C.D.S.); (F.G.C.); (M.C.); (B.R.); (M.F.); (S.D.A.); (F.T.); (A.F.); (M.F.); (F.Z.)
| | - Vassilissa Vinogradoff
- Physique des Interactions Ioniques et Moléculaires, PIIM, Université d’Aix-Marseille, 13013 Marseille, France;
| | - Julie C. Castillo-Rogez
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA; (J.C.C.-R.); (C.A.R.)
| | - Federico Tosi
- Istituto Nazionale di Astrofisica–Istituto di Astrofisica e Planetologia Spaziali, 00133 Rome, Italy; (M.C.D.S.); (F.G.C.); (M.C.); (B.R.); (M.F.); (S.D.A.); (F.T.); (A.F.); (M.F.); (F.Z.)
| | - Alessandro Frigeri
- Istituto Nazionale di Astrofisica–Istituto di Astrofisica e Planetologia Spaziali, 00133 Rome, Italy; (M.C.D.S.); (F.G.C.); (M.C.); (B.R.); (M.F.); (S.D.A.); (F.T.); (A.F.); (M.F.); (F.Z.)
| | - Michelangelo Formisano
- Istituto Nazionale di Astrofisica–Istituto di Astrofisica e Planetologia Spaziali, 00133 Rome, Italy; (M.C.D.S.); (F.G.C.); (M.C.); (B.R.); (M.F.); (S.D.A.); (F.T.); (A.F.); (M.F.); (F.Z.)
| | - Francesca Zambon
- Istituto Nazionale di Astrofisica–Istituto di Astrofisica e Planetologia Spaziali, 00133 Rome, Italy; (M.C.D.S.); (F.G.C.); (M.C.); (B.R.); (M.F.); (S.D.A.); (F.T.); (A.F.); (M.F.); (F.Z.)
| | - Carol A. Raymond
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA; (J.C.C.-R.); (C.A.R.)
| | - Christopher T. Russell
- Earth Planetary and Space Sciences, University of California, Los Angeles, CA 90095, USA;
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Reflectance Spectroscopy of Ammonium Salts: Implications for Planetary Surface Composition. MINERALS 2020. [DOI: 10.3390/min10100902] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Recent discoveries have demonstrated that the surfaces of Mars, Ceres and other celestial bodies, as well as asteroids and comets, are characterized by the presence of ammonium-bearing minerals. A careful study of remote data compared with the analyses of more accurate laboratory data might allow a better remote characterization of planetary bodies. In this paper, the reflectance spectra of some ammoniated hydrous and anhydrous salts, namely sal-ammoniac NH4Cl, larderellite (NH4)B5O7(OH)2·H2O, mascagnite (NH4)SO4, struvite (NH4)MgPO4·6H2O and tschermigite (NH4)Al(SO4)2·12H2O, were collected at 293 and at 193 K. The aim is to detect how the NH4 vibrational features are affected by the chemical and structural environment. All samples were recovered after cooling cycles and were characterized by X-ray powder diffraction. Reflectance spectra of the studied minerals show absorption features around 1.3, 1.6, 2.06, 2.14, 3.23, 5.8 and 7.27 μm, related to the ammonium group. Between them, the 2ν3 at ~1.56 μm and the ν3 + ν4 at ~2.13 μm are the most affected modes by crystal structure type, with their position being strictly related to both anionic group and the strength of the hydrogen bonds. The reflectance spectra of water-rich samples [struvite (NH4)MgPO4·6(H2O) and tschermigite (NH4)Al(SO4)2·12(H2O)] show only H2O fundamental absorption features in the area from 2 to 2.8 μm and a band from hygroscopic water at 3 μm. Thermal analyses (TA), thermal gravimetry (TG) and differential scanning calorimetry (DSC) allowed to evaluate the dehydration temperatures and the occurring phase transitions and decompositions in the analyzed samples. In almost all samples, endothermic peaks at distinct temperatures were registered associated to loss of water molecules, differently linked to the structures. Moreover, an endothermic peak at 465 K in sal-ammoniac was associated to the phase transition from CsCl to NaCl structure type.
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Burbine TH, Greenwood RC. Exploring the Bimodal Solar System via Sample Return from the Main Asteroid Belt: The Case for Revisiting Ceres. SPACE SCIENCE REVIEWS 2020; 216:59. [PMID: 32624627 PMCID: PMC7319314 DOI: 10.1007/s11214-020-00671-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 04/07/2020] [Indexed: 06/11/2023]
Abstract
Sample return from a main-belt asteroid has not yet been attempted, but appears technologically feasible. While the cost implications are significant, the scientific case for such a mission appears overwhelming. As suggested by the "Grand Tack" model, the structure of the main belt was likely forged during the earliest stages of Solar System evolution in response to migration of the giant planets. Returning samples from the main belt has the potential to test such planet migration models and the related geochemical and isotopic concept of a bimodal Solar System. Isotopic studies demonstrate distinct compositional differences between samples believed to be derived from the outer Solar System (CC or carbonaceous chondrite group) and those that are thought to be derived from the inner Solar System (NC or non-carbonaceous group). These two groups are separated on relevant isotopic variation diagrams by a clear compositional gap. The interface between these two regions appears to be broadly coincident with the present location of the asteroid belt, which contains material derived from both groups. The Hayabusa mission to near-Earth asteroid (NEA) (25143) Itokawa has shown what can be learned from a sample-return mission to an asteroid, even with a very small amount of sample. One scenario for main-belt sample return involves a spacecraft launching a projectile that strikes an object and flying through the debris cloud, which would potentially allow multiple bodies to be sampled if a number of projectiles are used on different asteroids. Another scenario is the more traditional method of landing on an asteroid to obtain the sample. A significant range of main-belt asteroids are available as targets for a sample-return mission and such a mission would represent a first step in mineralogically and isotopically mapping the asteroid belt. We argue that a sample-return mission to the asteroid belt does not necessarily have to return material from both the NC and CC groups to viably test the bimodal Solar System paradigm, as material from the NC group is already abundantly available for study. Instead, there is overwhelming evidence that we have a very incomplete suite of CC-related samples. Based on our analysis, we advocate a dedicated sample-return mission to the dwarf planet (1) Ceres as the best means of further exploring inherent Solar System variation. Ceres is an ice-rich world that may be a displaced trans-Neptunian object. We almost certainly do not have any meteorites that closely resemble material that would be brought back from Ceres. The rich heritage of data acquired by the Dawn mission makes a sample-return mission from Ceres logistically feasible at a realistic cost. No other potential main-belt target is capable of providing as much insight into the early Solar System as Ceres. Such a mission should be given the highest priority by the international scientific community.
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Affiliation(s)
- Thomas H. Burbine
- Department of Astronomy, Mount Holyoke College, South Hadley, MA 01075 USA
| | - Richard C. Greenwood
- Planetary and Space Sciences, School of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
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8
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Hänni N, Gasc S, Etter A, Schuhmann M, Schroeder I, Wampfler SF, Schürch S, Rubin M, Altwegg K. Ammonium Salts as a Source of Small Molecules Observed with High-Resolution Electron-Impact Ionization Mass Spectrometry. J Phys Chem A 2019; 123:5805-5814. [PMID: 31257892 DOI: 10.1021/acs.jpca.9b03534] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recent high-resolution in situ mass spectrometry at comet 67P/Churyumov-Gerasimenko visited by European Space Agency's Rosetta spacecraft raised the question, if sublimating ammonium salts can unequivocally be detected in the cometary coma. In laboratory experiments with the twin model of the space instrument, two prototypic ammonium salts NH4B, namely, ammonium chloride (B = Cl-) and ammonium formate (B = HCOO-) (as well as methodologically relevant isotopologues), were allowed to sublimate in vacuum while mass spectra were collected. High-resolution electron-impact ionization mass spectrometry provides an outstanding experimental tool to investigate the complex physicochemical processes occurring during the sublimation of ammonium salts. Sublimation of ammonium chloride led to the observation of the ammonium cation NH4+ and the chloramide molecule NH2Cl in the neutral gas mode of the instrument. These observations could be jointly interpreted as indirect evidence for the existence of a neutral gaseous parent species (either as the molecular complex NH3···HB or the double-ionic species NH4+···B-). However, the qualitative fragmentation pattern we present for 13C15N-ammonium formate suggests an alternative route of NH4+ production within the ionization region of the instrument, namely, by protonation/hydrogenation. Besides NH4+, other species were observed that were formed in protonation/hydrogenation reactions. Moreover, together with the two major species from the decomposition of the salt, ammonia and formic acid, three minor species also contributed to the fragmentation pattern: HCN/HNC, HOCN/HNCO, and CH3NO. Like chloramide, formamide (CH3NO) also is a secondary species probably formed in a pseudo-intramolecular chemical reaction while ammonia and the respective acid are in a state of association. HCN/HNC and HOCN/HNCO are ternary products coming out of formamide decomposition reactions. We discuss our experimental findings, summarized in a tentative chemical reaction network, in light of the available theoretical literature and highlight their relevance for the interpretation of in situ measurements in space research.
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Affiliation(s)
- Nora Hänni
- Physikalisches Institut , University of Bern , Sidlerstrasse 5 , CH-3012 Bern , Switzerland
| | - Sébastien Gasc
- Physikalisches Institut , University of Bern , Sidlerstrasse 5 , CH-3012 Bern , Switzerland
| | - Adrian Etter
- Physikalisches Institut , University of Bern , Sidlerstrasse 5 , CH-3012 Bern , Switzerland
| | - Markus Schuhmann
- Physikalisches Institut , University of Bern , Sidlerstrasse 5 , CH-3012 Bern , Switzerland
| | - Isaac Schroeder
- Physikalisches Institut , University of Bern , Sidlerstrasse 5 , CH-3012 Bern , Switzerland
| | - Susanne F Wampfler
- Center for Space and Habitability , University of Bern , Gesellschaftsstrasse 6 , CH-3012 Bern , Switzerland
| | - Stefan Schürch
- Department of Chemistry and Biochemistry , University of Bern , Freiestrasse 3 , CH-3012 Bern , Switzerland
| | - Martin Rubin
- Physikalisches Institut , University of Bern , Sidlerstrasse 5 , CH-3012 Bern , Switzerland
| | - Kathrin Altwegg
- Physikalisches Institut , University of Bern , Sidlerstrasse 5 , CH-3012 Bern , Switzerland
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9
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Juntunen HL, Leinen LJ, Pitts BK, O'Hanlon SM, Theiling BP, Barge LM, Videau P, Gaylor MO. Investigating the Kinetics of Montmorillonite Clay-Catalyzed Conversion of Anthracene to 9,10-Anthraquinone in the Context of Prebiotic Chemistry. ORIGINS LIFE EVOL B 2018; 48:321-330. [PMID: 30203410 DOI: 10.1007/s11084-018-9562-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Accepted: 08/28/2018] [Indexed: 11/25/2022]
Abstract
Carbonaceous meteorites contributed polycyclic aromatic hydrocarbons (PAHs) to the organic inventory of the primordial Earth where they may have reacted on catalytic clay mineral surfaces to produce quinones capable of functioning as redox species in emergent biomolecular systems. To address the feasibility of this hypothesis, we assessed the kinetics of anthracene (1) conversion to 9,10-anthraquinone (2) in the presence of montmorillonite clay (MONT) over the temperature range 25 to 250 °C. Apparent rates of conversion were concentration independent and displayed a sigmoidal relationship with temperature, and conversion efficiencies ranged from 0.027 to 0.066%. Conversion was not detectable in the absence of MONT or a sufficiently high oxidation potential (in this case, molecular oxygen (O2)). These results suggest a scenario in which meteoritic 1 and MONT interactions could yield biologically important quinones in prebiotic planetary environments.
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Affiliation(s)
- Hope L Juntunen
- Department of Biology, Dakota State University, Madison, SD, 57042, USA
- Department of Chemistry, Dakota State University, Madison, SD, 57042, USA
| | - Lucas J Leinen
- Department of Chemistry, Dakota State University, Madison, SD, 57042, USA
| | - Briann K Pitts
- Department of Biology, Dakota State University, Madison, SD, 57042, USA
| | - Samantha M O'Hanlon
- School of Psychological Science, Oregon State University, Corvallis, OR, 97331, USA
| | | | - Laura M Barge
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA
| | - Patrick Videau
- Department of Biology, Dakota State University, Madison, SD, 57042, USA.
- Department of Biology, Southern Oregon University, Ashland, OR, 97520, USA.
| | - Michael O Gaylor
- Department of Chemistry, Dakota State University, Madison, SD, 57042, USA.
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10
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Abstract
Spectral remote sensing in the visible/near-infrared (VNIR) and mid-IR (MIR) regions has enabled detection and characterisation of multiple clays and clay minerals on Earth and in the Solar System. Remote sensing on Earth poses the greatest challenge due to atmospheric absorptions that interfere with detection of surface minerals. Still, a greater variety of clay minerals have been observed on Earth than other bodies due to extensive aqueous alteration on our planet. Clay minerals have arguably been mapped in more detail on the planet Mars because they are not masked by vegetation on that planet and the atmosphere is less of a hindrance. Fe/Mg-smectite is the most abundant clay mineral on the surface of Mars and is also common in meteorites and comets where clay minerals are detected.
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Affiliation(s)
- Janice L Bishop
- SETI Institute, Carl Sagan Center, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
| | | | - John Carter
- Institut d'Astrophysique Spatiale, CNRS/Paris-Sud University, Orsay, France
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11
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Russell CT, Raymond CA, Ammannito E, Buczkowski DL, De Sanctis MC, Hiesinger H, Jaumann R, Konopliv AS, McSween HY, Nathues A, Park RS, Pieters CM, Prettyman TH, McCord TB, McFadden LA, Mottola S, Zuber MT, Joy SP, Polanskey C, Rayman MD, Castillo-Rogez JC, Chi PJ, Combe JP, Ermakov A, Fu RR, Hoffmann M, Jia YD, King SD, Lawrence DJ, Li JY, Marchi S, Preusker F, Roatsch T, Ruesch O, Schenk P, Villarreal MN, Yamashita N. Dawn arrives at Ceres: Exploration of a small, volatile-rich world. Science 2017; 353:1008-1010. [PMID: 27701107 DOI: 10.1126/science.aaf4219] [Citation(s) in RCA: 161] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 07/13/2016] [Indexed: 11/02/2022]
Abstract
On 6 March 2015, Dawn arrived at Ceres to find a dark, desiccated surface punctuated by small, bright areas. Parts of Ceres' surface are heavily cratered, but the largest expected craters are absent. Ceres appears gravitationally relaxed at only the longest wavelengths, implying a mechanically strong lithosphere with a weaker deep interior. Ceres' dry exterior displays hydroxylated silicates, including ammoniated clays of endogenous origin. The possibility of abundant volatiles at depth is supported by geomorphologic features such as flat crater floors with pits, lobate flows of materials, and a singular mountain that appears to be an extrusive cryovolcanic dome. On one occasion, Ceres temporarily interacted with the solar wind, producing a bow shock accelerating electrons to energies of tens of kilovolts.
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Affiliation(s)
- C T Russell
- Earth Planetary and Space Sciences, University of California, Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA.
| | - C A Raymond
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - E Ammannito
- Earth Planetary and Space Sciences, University of California, Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA
| | - D L Buczkowski
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723-6099, USA
| | - M C De Sanctis
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - H Hiesinger
- Institut für Planetologie, 48149 Münster, Germany
| | - R Jaumann
- Deutsches Zentrum fur Luft-und Raumfahrt, Institute of Planetary Research, 12489 Berlin, Germany
| | - A S Konopliv
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - H Y McSween
- Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996-1410, USA
| | - A Nathues
- Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
| | - R S Park
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - C M Pieters
- Brown University, Department of Earth, Environmental, and Planetary Sciences, Providence, RI 02912, USA
| | | | - T B McCord
- The Bear Fight Institute, Winthrop, WA 98862, USA
| | - L A McFadden
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
| | - S Mottola
- Deutsches Zentrum fur Luft-und Raumfahrt, Institute of Planetary Research, 12489 Berlin, Germany
| | - M T Zuber
- Massachussetts Institute of Technology, Cambridge, MA 02139, USA
| | - S P Joy
- Earth Planetary and Space Sciences, University of California, Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA
| | - C Polanskey
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - M D Rayman
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - J C Castillo-Rogez
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - P J Chi
- Earth Planetary and Space Sciences, University of California, Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA
| | - J P Combe
- The Bear Fight Institute, Winthrop, WA 98862, USA
| | - A Ermakov
- Massachussetts Institute of Technology, Cambridge, MA 02139, USA
| | - R R Fu
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10968, USA
| | - M Hoffmann
- Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
| | - Y D Jia
- Earth Planetary and Space Sciences, University of California, Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA
| | - S D King
- Virginia Tech, Geosciences, Blacksburg, VA 24061, USA
| | - D J Lawrence
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723-6099, USA
| | - J-Y Li
- Planetary Science Institute, Tucson, AZ 85719, USA
| | - S Marchi
- Southwest Research Institute, Boulder, CO 80302, USA
| | - F Preusker
- Deutsches Zentrum fur Luft-und Raumfahrt, Institute of Planetary Research, 12489 Berlin, Germany
| | - T Roatsch
- Deutsches Zentrum fur Luft-und Raumfahrt, Institute of Planetary Research, 12489 Berlin, Germany
| | - O Ruesch
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
| | - P Schenk
- Lunar and Planetary Institute, Houston, TX 77058, USA
| | - M N Villarreal
- Earth Planetary and Space Sciences, University of California, Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA
| | - N Yamashita
- Planetary Science Institute, Tucson, AZ 85719, USA
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12
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Hiesinger H, Marchi S, Schmedemann N, Schenk P, Pasckert JH, Neesemann A, O'Brien DP, Kneissl T, Ermakov AI, Fu RR, Bland MT, Nathues A, Platz T, Williams DA, Jaumann R, Castillo-Rogez JC, Ruesch O, Schmidt B, Park RS, Preusker F, Buczkowski DL, Russell CT, Raymond CA. Cratering on Ceres: Implications for its crust and evolution. Science 2016; 353:353/6303/aaf4759. [PMID: 27701089 DOI: 10.1126/science.aaf4759] [Citation(s) in RCA: 125] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Accepted: 07/29/2016] [Indexed: 11/02/2022]
Abstract
Thermochemical models have predicted that Ceres, is to some extent, differentiated and should have an icy crust with few or no impact craters. We present observations by the Dawn spacecraft that reveal a heavily cratered surface, a heterogeneous crater distribution, and an apparent absence of large craters. The morphology of some impact craters is consistent with ice in the subsurface, which might have favored relaxation, yet large unrelaxed craters are also present. Numerous craters exhibit polygonal shapes, terraces, flowlike features, slumping, smooth deposits, and bright spots. Crater morphology and simple-to-complex crater transition diameters indicate that the crust of Ceres is neither purely icy nor rocky. By dating a smooth region associated with the Kerwan crater, we determined absolute model ages (AMAs) of 550 million and 720 million years, depending on the applied chronology model.
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Affiliation(s)
- H Hiesinger
- Institut für Planetologie, Westfälische Wilhelms-Universität, Münster, Germany.
| | - S Marchi
- Southwest Research Institute, Boulder, CO 80302, USA
| | - N Schmedemann
- Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany
| | - P Schenk
- Lunar and Planetary Institute, Houston, TX 77058, USA
| | - J H Pasckert
- Institut für Planetologie, Westfälische Wilhelms-Universität, Münster, Germany
| | - A Neesemann
- Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany
| | - D P O'Brien
- Planetary Science Institute, Tucson, AZ 85719, USA
| | - T Kneissl
- Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany
| | - A I Ermakov
- Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - R R Fu
- Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - M T Bland
- U.S. Geological Survey, Astrogeology Science Center, Flagstaff, AZ 86001, USA
| | - A Nathues
- Max-Planck Institute for Solar System Research, Göttingen, Germany
| | - T Platz
- Max-Planck Institute for Solar System Research, Göttingen, Germany
| | | | - R Jaumann
- German Aerospace Center (DLR), Berlin, Germany. Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany
| | - J C Castillo-Rogez
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - O Ruesch
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
| | - B Schmidt
- Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - R S Park
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - F Preusker
- German Aerospace Center (DLR), Berlin, Germany
| | - D L Buczkowski
- John Hopkins Applied Physics Laboratory, Laurel, MD 20723, USA
| | - C T Russell
- Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095, USA
| | - C A Raymond
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
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13
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Ammannito E, DeSanctis MC, Ciarniello M, Frigeri A, Carrozzo FG, Combe JP, Ehlmann BL, Marchi S, McSween HY, Raponi A, Toplis MJ, Tosi F, Castillo-Rogez JC, Capaccioni F, Capria MT, Fonte S, Giardino M, Jaumann R, Longobardo A, Joy SP, Magni G, McCord TB, McFadden LA, Palomba E, Pieters CM, Polanskey CA, Rayman MD, Raymond CA, Schenk PM, Zambon F, Russell CT. Distribution of phyllosilicates on the surface of Ceres. Science 2016; 353:353/6303/aaf4279. [PMID: 27701086 DOI: 10.1126/science.aaf4279] [Citation(s) in RCA: 146] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 07/29/2016] [Indexed: 11/02/2022]
Abstract
The dwarf planet Ceres is known to host phyllosilicate minerals at its surface, but their distribution and origin have not previously been determined. We used the spectrometer onboard the Dawn spacecraft to map their spatial distribution on the basis of diagnostic absorption features in the visible and near-infrared spectral range (0.25 to 5.0 micrometers). We found that magnesium- and ammonium-bearing minerals are ubiquitous across the surface. Variations in the strength of the absorption features are spatially correlated and indicate considerable variability in the relative abundance of the phyllosilicates, although their composition is fairly uniform. These data, along with the distinctive spectral properties of Ceres relative to other asteroids and carbonaceous meteorites, indicate that the phyllosilicates were formed endogenously by a globally widespread and extensive alteration process.
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Affiliation(s)
- E Ammannito
- Earth Planetary and Space Sciences, University of California-Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA.
| | - M C DeSanctis
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - M Ciarniello
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - A Frigeri
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - F G Carrozzo
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - J-Ph Combe
- The Bear Fight Institute, Winthrop, WA 98862, USA
| | - B L Ehlmann
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - S Marchi
- Southwest Research Institute, Boulder, CO 80302, USA
| | - H Y McSween
- Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996-1410, USA
| | - A Raponi
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - M J Toplis
- Institut de Recherche en Astrophysique et Planétologie (UMR 5277), Université de Toulouse, F-31400 Toulouse, France
| | - F Tosi
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - J C Castillo-Rogez
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - F Capaccioni
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - M T Capria
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - S Fonte
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - M Giardino
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - R Jaumann
- Institute of Planetary Research, Deutsches Zentrum für Luft- und Raumfahrt, 12489 Berlin, Germany
| | - A Longobardo
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - S P Joy
- Earth Planetary and Space Sciences, University of California-Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA
| | - G Magni
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - T B McCord
- The Bear Fight Institute, Winthrop, WA 98862, USA
| | - L A McFadden
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
| | - E Palomba
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - C M Pieters
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02912, USA
| | - C A Polanskey
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - M D Rayman
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - C A Raymond
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - P M Schenk
- Lunar and Planetary Institute, Houston, TX 77058, USA
| | - F Zambon
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, 00133 Roma, Italy
| | - C T Russell
- Earth Planetary and Space Sciences, University of California-Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA
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14
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Bright carbonate deposits as evidence of aqueous alteration on (1) Ceres. Nature 2016; 536:54-7. [PMID: 27362221 DOI: 10.1038/nature18290] [Citation(s) in RCA: 212] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 04/25/2016] [Indexed: 11/09/2022]
Abstract
The typically dark surface of the dwarf planet Ceres is punctuated by areas of much higher albedo, most prominently in the Occator crater. These small bright areas have been tentatively interpreted as containing a large amount of hydrated magnesium sulfate, in contrast to the average surface, which is a mixture of low-albedo materials and magnesium phyllosilicates, ammoniated phyllosilicates and carbonates. Here we report high spatial and spectral resolution near-infrared observations of the bright areas in the Occator crater on Ceres. Spectra of these bright areas are consistent with a large amount of sodium carbonate, constituting the most concentrated known extraterrestrial occurrence of carbonate on kilometre-wide scales in the Solar System. The carbonates are mixed with a dark component and small amounts of phyllosilicates, as well as ammonium carbonate or ammonium chloride. Some of these compounds have also been detected in the plume of Saturn’s sixth-largest moon Enceladus. The compounds are endogenous and we propose that they are the solid residue of crystallization of brines and entrained altered solids that reached the surface from below. The heat source may have been transient (triggered by impact heating). Alternatively, internal temperatures may be above the eutectic temperature of subsurface brines, in which case fluids may exist at depth on Ceres today.
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15
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Mysterious bright spots on Ceres are probably salt. Nature 2015. [DOI: 10.1038/nature.2015.18980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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16
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Ammoniated phyllosilicates with a likely outer Solar System origin on (1) Ceres. Nature 2015; 528:241-4. [DOI: 10.1038/nature16172] [Citation(s) in RCA: 239] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Accepted: 10/29/2015] [Indexed: 11/08/2022]
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17
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Localized sources of water vapour on the dwarf planet (1) Ceres. Nature 2014; 505:525-7. [PMID: 24451541 DOI: 10.1038/nature12918] [Citation(s) in RCA: 229] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Accepted: 11/26/2013] [Indexed: 11/08/2022]
Abstract
The 'snowline' conventionally divides Solar System objects into dry bodies, ranging out to the main asteroid belt, and icy bodies beyond the belt. Models suggest that some of the icy bodies may have migrated into the asteroid belt. Recent observations indicate the presence of water ice on the surface of some asteroids, with sublimation a potential reason for the dust activity observed on others. Hydrated minerals have been found on the surface of the largest object in the asteroid belt, the dwarf planet (1) Ceres, which is thought to be differentiated into a silicate core with an icy mantle. The presence of water vapour around Ceres was suggested by a marginal detection of the photodissociation product of water, hydroxyl (ref. 12), but could not be confirmed by later, more sensitive observations. Here we report the detection of water vapour around Ceres, with at least 10(26) molecules being produced per second, originating from localized sources that seem to be linked to mid-latitude regions on the surface. The water evaporation could be due to comet-like sublimation or to cryo-volcanism, in which volcanoes erupt volatiles such as water instead of molten rocks.
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18
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19
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Thomas PC, Parker JW, McFadden LA, Russell CT, Stern SA, Sykes MV, Young EF. Differentiation of the asteroid Ceres as revealed by its shape. Nature 2005; 437:224-6. [PMID: 16148926 DOI: 10.1038/nature03938] [Citation(s) in RCA: 239] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2005] [Accepted: 06/10/2005] [Indexed: 11/08/2022]
Abstract
The accretion of bodies in the asteroid belt was halted nearly 4.6 billion years ago by the gravitational influence of the newly formed giant planet Jupiter. The asteroid belt therefore preserves a record of both this earliest epoch of Solar System formation and variation of conditions within the solar nebula. Spectral features in reflected sunlight indicate that some asteroids have experienced sufficient thermal evolution to differentiate into layered structures. The second most massive asteroid--4 Vesta--has differentiated to a crust, mantle and core. 1 Ceres, the largest and most massive asteroid, has in contrast been presumed to be homogeneous, in part because of its low density, low albedo and relatively featureless visible reflectance spectrum, similar to carbonaceous meteorites that have suffered minimal thermal processing. Here we show that Ceres has a shape and smoothness indicative of a gravitationally relaxed object. Its shape is significantly less flattened than that expected for a homogeneous object, but is consistent with a central mass concentration indicative of differentiation. Possible interior configurations include water-ice-rich mantles over a rocky core.
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Affiliation(s)
- P C Thomas
- Center for Radiophysics and Space Research, Cornell University, Ithaca, New York 14853, USA.
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20
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21
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Engel S, Lunine JI, Norton DL. Silicate interactions with ammonia-water fluids on early Titan. ACTA ACUST UNITED AC 1994. [DOI: 10.1029/93je03433] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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