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Abundances of elements in solar system. Space Sci Rev
Abstract
The present status of abundance information for elements in meteorites and in the Sun is reviewed, and a new table of abundances of the elements, which should be characteristic of the primitive solar nebula, is compiled and presented. Special attention is called to the elemental abundances in the silicon-to-calcium region, where many of the abundances are rather poorly determined, and where these abundances have an impact on theories of nucleosynthesis of the elements. To each elemental isotope is assigned a mechanism of nucleosynthesis which may have been responsible for production of most of that isotope, and brief comments are made concerning the present status of understanding of the different mechanisms of nucleosynthesis.
... These results present five additional candidates with netexothermic pathways for spectroscopic detection: c-C 3 HCN, c-C 3 HF, ap-c-C 3 HOH, sp-c-C 3 HOH, and c-C 3 HNH 2 . The cyano (McKellar 1940;Adams 1941;Jefferts et al. 1970;Henkel et al. 1988), fluorine (Suess & Urey 1956;Cameron 1973;Jr & York 1981), hydroxy (Weinreb et al. 1963;Heiles 1968;Dickey et al. 1981;Crutcher et al. 1981;Storey et al. 1981), and amino (van Dishoeck et al. 1993;Melosso et al. 2020) radicals exist, although in varying concentrations, in interstellar space, underpinning the detectability of the products of reactions involving them. Figure 2 displays the reaction pathway of the addition of ·CN to c-C 3 H 2 to form c-C 3 HCN. ...
... kcal mol −1 ) upon addition of ·F to c-C 3 H 2 , as well as the large dipole moment of c-C 3 HF, shows promise for the formation and spectroscopic detectability of c-C 3 HF. However, the small interstellar abundances of fluorine, even with atomic (Suess & Urey 1956;Cameron 1973;Jr & York 1981) and small molecule presence (Neufeld et al. 1997), make the probability of collision between the necessary species minimal. The circumstances surrounding the formation of fluorine in space (Woolsey & Haxton 1988;Woolsey & Weaver 1995;Meynet & Arnould 2000;Forestini et al. 1992) result in low concentrations of fluorine in the overall chemical budget of the universe. ...
Five substituted cyclopropenylidene derivatives ( c -C 3 HX, X=CN, OH, F, NH 2 ), all currently undetected in the interstellar medium (ISM), are found herein to have mechanistically viable, gas-phase formation pathways through neutral–neutral additions of ·X onto c -C 3 H 2 . The detection and predicted formation mechanism of c -C 3 HC 2 H introduces a need for the chemistry of c -C 3 H 2 and any possible derivatives to be more fully explored. Chemically accurate CCSD(T)-F12/cc-pVTZ-F12 calculations provide exothermicities of additions of various radical species to c -C 3 H 2 , alongside energies of submerged intermediates that are crossed to result in product formation. Of the novel reaction mechanisms proposed, the addition of the cyano radical is the most exothermic at -16.10 kcal mol ⁻¹ . All five products are found to or are expected to have at least one means of associating barrierlessly to form a submerged intermediate, a requirement for the cold chemistry of the ISM. The energetically allowed additions arise as a result of the strong electrophilicity of the radical species as well as the product stability gained through substituent-ring conjugation.
... Argon is often present in the atmospheres of planets and satellites, for example in the atmospheres of Earth, Mars and Titan. 30,[44][45][46][47][48][49] Molecular nitrogen is the dominant species in the atmosphere of the Earth, but also in the atmosphere of Titan. 13,19,[45][46][47][48][50][51][52] While CO has been detected in comets, [53][54][55] is widely distributed across the ISM; 56,57 and is also present in the atmospheres of various planets and satellites including the Earth, 58 Venus, 59 and Titan. ...
... 30,[44][45][46][47][48][49] Molecular nitrogen is the dominant species in the atmosphere of the Earth, but also in the atmosphere of Titan. 13,19,[45][46][47][48][50][51][52] While CO has been detected in comets, [53][54][55] is widely distributed across the ISM; 56,57 and is also present in the atmospheres of various planets and satellites including the Earth, 58 Venus, 59 and Titan. [60][61][62] To the authors' knowledge, no bimolecular reactions involving CH 2 CN 2+ have previously been reported. ...
The reactivity, energetics and dynamics of bimolecular reactions between CH2CN2+ and three neutral species (Ar, N2 and CO) have been studied using a position sensitive coincidence methodology at centre-of-mass collision energies of 4.3 – 5.0 eV. This is the first study of bimolecular reactions involving CH2CN2+, a species relevant to the ionospheres of planets and satellites, including Titan. All of the collision systems investigated display two collision-induced dissociation (CID) channels, resulting in the formation of C+ + CH2N+ and H+ + HC2N+. Evidence for channels involving further dissociation of the CID product HC2N+, forming H + CCN+, were detected in the N2 and CO systems. Proton-transfer from the dication to the neutral occurs in all three of the systems via a direct mechanism. Additionally, there are product channels resulting from single electron transfer following collisions of CH2CN2+ with both N2 and CO, but interestingly no electron transfer following collisions with Ar. Electronic structure calculations of the lowest energy electronic states of CH2CN2+ reveal six local geometric minima: both doublet and quartet spin states for cyclic, linear (CH2CN), and linear isocyanide (CH2NC) molecular geometries. The lowest energy electronic state was determined to be the doublet state of the cyclic dication. The ready generation of C+ ions by collision-induced dissociation suggests that the cyclic or linear isocyanide dication geometries are present in the [CH2CN]2+ beam.
... Fluorine as a unique halogen is the 13th most abundant element in the world and relatively rare compared to other elements of nearby atomic weight [1,2]. Despite the relatively high abundance of fluorine atom in Earth's crust, four factors, (1) water insolubility of fluorine-rich natural sources including the fluorapatite (Ca 5 (PO 4 ) 3 F), fluorospar (CaF 2 ), and cryolite (Na 3 AlF 6 ), (2) high oxidation potential [3], (3) high hydration energy [4], and (4) high electronegativity, make it unavailable for natural chemical reactions and biological evolution. ...
... A synthetic method for construction of seven-membered cyclic amines 46 bearing chiral tetrasubstituted C-F centers was reported by Du and coworkers which were resulted from reaction of 3-fluorooxindoles 10 and dibenzo[b,f] [1,4] oxazepines 45 catalyzed by the bifunctional Cinchona alkaloid-derived thiourea catalyst 47 (Scheme 13) [61]. The stereogenic centers configurations of products were studied by X-ray crystallographic analysis based on recrystallization from absolute methanol. ...
For its unique role in developing and designing new bioactive materials and healthcare products, fluoro-organic compounds have attracted remarkable interest. Along with ever-increasing demand for a wider availability of fluorine-containing structural units, a large diversity of methods has been introduced to incorporate fluorine atoms specially in a stereoselective fashion. Among them, catalytic Mannich reaction can proceed with a broad variety of reactants and open clear paths for the synthesis of versatile amine synthons in the synthesis of natural product and pharmaceutical molecules. This review provides an overview of the employment of catalytic asymmetric Mannich reactions in the synthesis of fluorine-containing amine compounds and highlights the conceivable distinct mechanisms.
Graphic abstract
... Argon constitutes B1% of the Earth's atmosphere and is also found in the atmospheres of the Moon, Mercury and Mars. [27][28][29][30][31] In the upper reaches of these atmospheres, the formation of the Ar 2+ dication is likely, as recognised by Thissen et al. 14 The bimolecular reactivity of Ar 2+ with a variety of rare gases and simple molecules has been studied previously. [32][33][34][35][36][37][38] Most of the early investigations of Ar 2+ -neutral collisions were carried out at 0.1-20 keV collision energies. ...
... Nitrogen (N 2 ) is the dominant species in the atmospheres of the Earth and Titan, and is present in the atmospheres of other planets and satelites. 14,15,[28][29][30][31][45][46][47] The reactions resulting from collisions of Ar 2+ with N 2 have been the subject of previous investigation. As noted above, at high collision energies (keV), SET and DET pathways were identified, as expected, although these studies did not probe the reactivity at an electronic stateselective level. ...
Collisions between Ar2+ and N2 have been studied using a coincidence technique at a centre-of-mass (CM) collision energy of 5.1 eV. Four reaction channels generating pairs of monocations are observed: Ar+ + N2+, Ar+ + N+, ArN+ + N+ and N+ + N+. The formation of Ar+ + N2+ is the most intense channel, displaying forward scattering but with a marked tail to higher scattering angles. This scattering, and other dynamics data, is indicative of direct electron transfer competing with a 'sticky' collision between the Ar2+ and N2 reactants. Here Ar+ is generated in its ground (2P) state and N2+ is primarily in the low vibrational levels of the C2Σu+ state. A minor channel involving the initial population of higher energy N2+ states, lying above the dissociation asymptote to N+ + N, which fluoresce to stable states of N2+ is also identified. The formation of Ar+ + N+ by dissociative single electron transfer again reveals the involvement of two different pathways for the initial electron transfer (direct or complexation). This reaction pathway predominantly involves excited states of Ar2+ (1D and 1S) populating N2+* in its dissociative C2Σu+, 22Πg and D2Πg states. Formation of ArN+ + N+ proceeds via a direct mechanism. The ArN+ is formed, with significant vibrational excitation, in its ground (X3Σ-) state. Formation of N+ + N+ is also observed as a consequence of double electron transfer forming N22+. The exoergicity of the subsequent N22+ dissociation reveals the population of the A1Πu and D3Πg dication states.
... Using the solar abundances shown in Figure 4 (Cameron 1973), we estimate the amount of bulk rock required to mine the elemental ingredients of the superconductor. For BSCCO superconductors, the rarest element is bismuth (Bi), so its abundance would dictate the bulk rock required. ...
... Kametani et al. 2015). Carbon is included for the case of Carbon nanotubes; the benefit to Relative abundance of chemical elements in the Solar System (Cameron 1973). The x-axis represents atomic number and the y-axis represents abundance of elements for every 10 6 atoms of Si. ...
Mars lacks a substantial magnetic field; as a result, the solar wind ablates the Martian atmosphere, making the surface uninhabitable. Therefore, any terraforming attempt will require an artificial Martian magnetic shield. The fundamental challenge of building an artificial magnetosphere is to condense planetary-scale currents and magnetic fields down to the smallest mass possible. Superconducting electromagnets offer a way to do this. However, the underlying physics of superconductors and electromagnets limits this concentration. Based upon these fundamental limitations, we show that the amount of superconducting material is proportional to $B_c^{-2}a^{-3}$, where $B_c$ is the critical magnetic field for the superconductor and $a$ is the loop radius of a solenoid. Since $B_c$ is set by fundamental physics, the only truly adjustable parameter for the design is the loop radius; a larger loop radius minimizes the amount of superconducting material required. This non-intuitive result means that the "intuitive" strategy of building a compact electromagnet and placing it between Mars and the Sun at the first Lagrange point is unfeasible. Considering reasonable limits on $B_c$, the smallest possible loop radius is $\sim$10 km, and the magnetic shield would have a mass of $\sim 10^{19}$ g. Most high-temperature superconductors are constructed of rare elements; given solar system abundances, building a superconductor with $\sim 10^{19}$ g would require mining a solar system body with several times $10^{25}$ g; this is approximately 10% of Mars. We find that the most feasible design is to encircle Mars with a superconducting wire with a loop radius of $\sim$ 3400 km. The resulting wire diameter can be as small as $\sim$5 cm. With this design, the magnetic shield would have a mass of $\sim 10^{12}$ g and would require mining $\sim 10^{18}$ g, or only 0.1\% of Olympus Mons.
... Argon constitutes B1% of the Earth's atmosphere and is one of the most abundant elements in the universe. 23,24 Argon is also abundant in the atmospheres of the Moon, Mercury and Mars. [25][26][27] In these atmospheres, the formation of the Ar 2+ dication is likely, as recognised by Thissen et al. 12 The bimolecular reactivity of Ar 2+ was one of the first dicationic collision systems to be investigated, as beams of Ar 2+ are relatively easy to generate using electron ionisation. ...
... Oxygen is the third most abundant element in the universe, it is a major component of the atmosphere of the Earth and is also present in the atmosphere of other planets and satellites. 24,25 The reactions between Ar 2+ and O 2 have been studied in experiments over a range of supra-thermal energies. 29,30,[32][33][34] In the earliest work, no chemical bond formation was observed, and the ion yields were explained using models involving varying contributions from SET and DET. ...
The reactivity, energetics and dynamics of the bimolecular reactions between Ar2+ and O2 have been studied using a position sensitive coincidence methodology at a collision energy of 4.4 eV. Four bimolecular reaction channels generating pairs of product ions are observed, forming: Ar+ + O2+, Ar+ + O+, ArO+ + O+ and O+ + O+. The formation of Ar+ + O2+ is a minor channel, involving forward scattering, and generates O2+ in its ground electronic state. This single electron transfer process is expected to by facile by Landau-Zener arguments, but the intensity of this channel is low because the electron transfer pathways involve multi-electron processes. The formation of Ar+ + O+ + O, is the most intense channel following interactions of Ar2+ with O2, in agreement with previous experiments. Many different combinations of Ar2+ and product electronic states contribute to the product flux in this channel. Major dissociation pathways of the nascent O2+* ion involve the ion’s first and second dissociation limits. Unusually, the experimental results clearly show the involvement of a short-lived collision complex [ArO2]2+ in this channel. The formation of O+ and ArO+ involves direct abstraction of O– from O2 by Ar2+. There is scant evidence of the involvement of a collision complex in this bond forming pathway. The ArO+ product appears to be formed in the first excited electronic state (2Π). The formation of O+ + O+ results from dissociative double electron transfer via an O22+ intermediate. The exoergicity of the dissociation of the nascent O22+ intermediate is in good agreement with previous work investigating the unimolecular dissociation of this dication.
... The value of the rate constant calculated in Figure 9 and other parameters calculated for this model are shown in Table 5. The behavior of dependences (43), (44), and (45) in relative units calculated for the obtained parameters are presented in Figure 10. ...
... Minor changes can be explained by the different element abundances. Sharp & Huebner (1990) employed element abundances based on Cameron (1973), wheres FastChem Cond uses the ones from Asplund et al. (2009). Other notable differences are the different sets of gas phase species and condensates as well as the underlying thermochemical data, the fitted equilibrium constants are based on. ...
Cool astrophysical objects, such as (exo)planets, brown dwarfs, or asymptotic giant branch stars, can be strongly affected by condensation. Condensation does not only directly affect the chemical composition of the gas phase by removing elements but the condensed material also influences other chemical and physical processes in these object. This includes, for example, the formation of clouds in planetary atmospheres and brown dwarfs or the dust-driven winds of evolved stars. In this study we introduce FastChem Cond, a new version of the FastChem equilibrium chemistry code that adds a treatment of equilibrium condensation. Determining the equilibrium composition under the impact of condensation is complicated by the fact that the number of condensates that can exist in equilibrium with the gas phase is limited by a phase rule. However, this phase rule does not directly provide information on which condensates are stable. As a major advantage of FastChem Cond is able to automatically select the set stable condensates satisfying the phase rule. Besides the normal equilibrium condensation, FastChem Cond can also be used with the rainout approximation that is commonly employed in atmospheres of brown dwarfs or (exo)planets. FastChem Cond is available as open-source code, released under the GPLv3 licence. In addition to the C++ code, FastChem Cond also offers a Python interface. Together with the code update we also add about 290 liquid and solid condensate species to FastChem.
... We assume that the lunar core is an iron alloy that starts fully liquid with no chemical or thermal stratification. To build our models, we assume that sulfur is the major light element in the core, given its siderophile behavior and cosmochemical abundance (e.g., Pommier 2018;Cameron 1973). Our models also include trace amounts of potassium as a source of radiogenic heating. ...
An internally generated magnetic field once existed on the Moon. This field reached high intensities (∼10–100 μ T, perhaps intermittently) from ∼4.3 to 3.6 Gyr ago and then weakened to ≲5 μ T before dissipating by ∼1.9–0.8 Gyr ago. While the Moon’s metallic core could have generated a magnetic field via a dynamo powered by vigorous convection, models of a core dynamo often fail to explain the observed characteristics of the lunar magnetic field. In particular, the core alone may not contain sufficient thermal, chemical, or radiogenic energy to sustain the high-intensity fields for >100 Myr. A recent study by Scheinberg et al. suggested that a dynamo hosted in electrically conductive, molten silicates in a basal magma ocean (BMO) may have produced a strong early field. However, that study did not fully explore the BMO’s coupled evolution with the core. Here we show that a coupled BMO–core dynamo driven primarily by inner core growth can explain the timing and staged decline of the lunar magnetic field. We compute the thermochemical evolution of the lunar core with a 1D parameterized model tied to extant simulations of mantle evolution and BMO solidification. Our models are most sensitive to four parameters: the abundances of sulfur and potassium in the core, the core’s thermal conductivity, and the present-day heat flow across the core–mantle boundary. Our models best match the Moon’s magnetic history if the bulk core contains ∼6.5–8.5 wt% sulfur, in agreement with seismic structure models.
... expert pilots: Di Nocera, Camilli, and Terenzi, 2007)(see chapter 3). Other related factors such as motivation level (Bandura, 1986;Mayer, 2003;Pintrich, 2000), related to individual interest to perform a given task; confidence to succeed the task; emotion (Damasio, 1995), cognitive performance affected by emotion's valence; decision making (Isen, 1993); stress level, where a high level is usually associated to a reduction in cognitive resources (Kahneman, 1973); anxiety level, which is related to a drop in available cognitive resources, with increasing level (Shackman et al., 2006), vigilance (Galy, Camps, & Mélan, 2004), which refers to the physiological state of our organism, related to circadian rhythm, being generally higher during the day than at night (Mackworth, 1950); fatigue level, which is a consequence of coping with a rise in working load, leading to an increase in experienced cognitive load (Cameron, 1973;Hockey, 1993). CL is also influenced by acts on individuals' self-regulated process (van Merriënboer & Sluijsmans, 2009). ...
This thesis has been conducted to analyze the cognitive load of train travelers in one of the most visited train station in Paris, Île-de-France: Saint-Michel Notre Dame. In order to anticipate the risk associated to overcrowding and security hazard in this megacity, we investigated how travelers' expertise modulates cognitive load during information processing. Through four experiments, we investigated variations in travelers' cognitive load in an ecological context, in both field and a validated virtual experiment. Cognitive load was assessed through physiological, subjective and behavioral aspects. Learning effects associated to cognitive load such as split-attention, instructional design, modality effect, redundancy effect and expertise reversal effect, were also discussed in our empirical studies for optimal cognitive load evaluation in train travelers. Travelers¿ cognitive load was evaluated through different environmental vagary levels, ranging from no vagary to successive vagaries situations. Our empirical studies allowed us to put in light variations in cognitive load between the different levels of expertise in travelers, with a higher cognitive load in novice or occasional travelers than in expert or regular travelers, in no vagary context. An expertise reversal effect, where experts expressed a higher cognitive load than novices, arises with increase in environmental vagary level. Novice travelers, however, showed no significant difference in cognitive load level, with varying environmental vagary level. We discussed how reducing the gap between experts and novices could encourage expert travelers to be more aware of their surrounding environment in moment of no vagary as well as non-optimal situations, to reduce the risk of abrupt rise in cognitive load. This thesis represents a mix between fundamental and applied research, to unravel the mechanism underlying cognitive load variations in a real-life context.
... [4][5][6][7] for earlier work on the optical spectroscopy of dense alkali-metal-noble-gas mixtures). Especially the effect of a high-pressure environment * ockenfels@iap.uni-bonn.de of the lightest noble gas helium acting as a buffer gas on the spectra of other elements is of great interest in astronomy as it is the second-most abundant element and represents 24% of the total baryonic mass in the universe [8]. ...
Spectroscopy of alkali-metal–buffer-gas mixtures at high pressures from single-digit to several hundred bars in the regime of substantial collisional broadening is relevant in a wide range of fields, ranging from collisional redistribution cooling to laboratory astrophysics. Here we report on spectroscopic measurements of dense rubidium–noble-gas mixtures recorded in a pressure cell equipped with soldered sapphire optical viewports, which allows for the controlled realization of extreme conditions of high temperature and high pressure in a table top laboratory experiment. In the gas cell, we have recorded absorption and emission spectra of rubidium subject to 188 bars of helium buffer-gas pressure at 548-K temperature. The spectra to good accuracy follow a Boltzmann-type Kennard-Stepanov frequency scaling of the ratio of absorption and emission spectral profiles. Further, the long optical path length in the cell allowed us to both record spectra of rubidium-argon mixtures at moderate temperatures and high pressures and observe redistributional laser cooling in this system.
... [56][57][58] Molecular nitrogen (N 2 ) is important in the atmospheres of terrestrial bodies in the solar system, especially the Earth and Titan where it is the dominant species. 21,22,54,55,[59][60][61][62][63] The reactions resulting from dication collisions with argon have been well studied. Single electron-transfer (SET) was observed in collisions with rare gas dications: Ne 2+ , Ar 2+ , Kr 2+ or Xe 2+ . ...
The reactivity, energetics and dynamics of bimolecular reactions between S2+ and three neutral species (Ar, H2 and N2) have been studied using a position-sensitive coincidence methodology at centre-of-mass collision energies below 6 eV. This is the first study of bimolecular reactions involving S2+, a species detected in planetary ionospheres, the interstellar medium, and in anthropogenic manufacturing processes. The reactant dication beam employed consists predominantly of S2+ in the ground 3P state, but some excited states are also present. Most of the observed reactions involve the ground state of S2+, but the dissociative electron transfer reactions appear to exclusively involve excited states of this atomic dication. We observe exclusively single electron-transfer between S2+ and Ar, a process which exhibits strong forward scatting typical of the Landau-Zener style dynamics observed for other dicationic electron transfer reactions. Following collisions between S2+ + H2, non-dissociative and dissociative single electron-transfer reactions were detected. The dynamics here show evidence for the formation of a long-lived collision complex, [SH2]2+, in the dissociative single electron-transfer channel. The formation of SH+ was not observed. In contrast, the collisions of S2+ + N2 result in the formation of SN+ + N+ in addition to the products of single electron-transfer reactions.
... On Earth, 40 Ar is 300 times more abundant than 36 Ar (Lee et al. 2006), and as no signal from 40 ArH + was visible, 36 ArH + seemed an unlikely carrier. Barlow et al. (2013), however, recognized that 36 Ar is the dominant isotope in the ISM (Cameron 1973) and identified the J = 1 → 0 and 2 → 1 rotational lines of 36 ArH + at 617.5 and 1234.6 GHz, respectively, in the Herschel/SPIRE spectra of the Crab Nebula. A citation is only given to the CDMS database, as no laboratory data appeared to exist for 36 ArH + . ...
To date, 241 individual molecular species, composed of 19 different elements, have been detected in the interstellar and circumstellar medium by astronomical observations. These molecules range in size from two atoms to 70 and have been detected across the electromagnetic spectrum from centimeter wavelengths to the ultraviolet. This census presents a summary of the first detection of each molecular species, including the observational facility, wavelength range, transitions, and enabling laboratory spectroscopic work, as well as listing tentative and disputed detections. Tables of molecules detected in interstellar ices, external galaxies, protoplanetary disks, and exoplanetary atmospheres are provided. A number of visual representations of these aggregate data are presented and briefly discussed in context.
... They are nitric oxide (NO), nitrous oxide (N2O), nitroxyl (HNO), nitrous acid (HONO), fulminic acid (HCNO), and hydroxylamine (NH2OH) (Fig. 1). What makes this matter remarkable is the fact that oxygen and nitrogen are, respectively, the second and fourth most abundant chemical elements in the visible Universe (not accounting for unreactive He and Ne) (Cameron 1973). Even though the availability of each element may differ considerably throughout a galaxy (Meyer, Jura & Cardelli 1998), it is safe to assume that both N and O are readily available in any given ISM object. ...
The interstellar chemistry of nitrogen is considerably less understood than the chemistry of other common elements, such as carbon and oxygen. Even though a relatively large number of species containing nitrogen atoms have already been detected in the interstellar medium, only six of them bear a nitrogen-oxygen (N-O) bond. Some astrophysical and primeval Earth models suggest that NO species, such as hydroxylamine (NH 2 OH), are potential precursors of prebiotic amino acids, and even peptides. In this work we have analyzed an apolar ice mixture of N2:CO of astrophysical interest to investigate possible formation mechanisms of NO bearing molecules due to processing of the sample by 64 Ni 24+ 538 MeV ions (8.4 MeV/u) at 14 K. The results show the formation of simple nitrogen oxides (, but no CN-O species of any kind. We have also determined the formation cross-sections of some of the products, as well as the destruction cross-sections of precursors and products. The results presented here are discussed in light of our previous work on the processing of a NH3:CO ice mixture, which have found no NO bearing molecules at all.
... The modern approach to the study of CNO abundances started with Suess and Urey (1956), whose tables of abundances provided fundamental constraints to theories of nucleosynthesis in stars. Cameron (1968), in his pioneering work, measured the abundances of several elements in the solar photosphere, including C, N, and O (see also Cameron, 1973). Lambert (1968) and Lambert (1978) gave a summary of all accessible atomic and molecular signatures of carbon, nitrogen, and oxygen, identifying the best ones to measure abundances. ...
Due to their production sites, as well as to how they are processed and destroyed in stars, the light elements are excellent tools to investigate a number of crucial issues in modern astrophysics: from stellar structure and non-standard processes in stellar interiors to age dating of stars; from pre-main sequence evolution to the star formation histories of young clusters and associations and to multiple populations in globular clusters; from Big Bang nucleosynthesis to the formation and chemical enrichment history of the Milky Way Galaxy, just to cite some relevant examples. In this paper, we focus on lithium, beryllium, and boron and on carbon, nitrogen, and oxygen. LiBeB are rare elements, with negligible abundances with respect to hydrogen; on the contrary, CNO are among the most abundant elements in the Universe. Pioneering observations of light-element surface abundances in stars started almost 70 years ago and huge progress has been achieved since then. Indeed, for different reasons, precise measurements of LiBeB and CNO are difficult, even in our Sun; however, the advent of state-of-the-art ground- and space-based instrumentation has allowed the determination of high-quality abundances in stars of different type, belonging to different Galactic populations. Noticeably, the recent large spectroscopic surveys performed with multifiber spectrographs have yielded detailed and homogeneous information on the abundances of Li and CNO for statistically significant samples of stars; this has allowed us to obtain new results and insights and, at the same time, raise new questions and challenges. A complete understanding of the light-element patterns and evolution in the Universe has not been still achieved. Perspectives for further progress will open up soon thanks to the new generation instrumentation that is under development and will come online in the coming years.
... The modern approach to the study of CNO abundances started with Suess and Urey (1956), whose tables of abundances provided fundamental constraints to theories of nucleosynthesis in stars. Cameron (1968), in his pioneering work, measured the abundances of several elements in the solar photosphere, including C, N, and O (see also Cameron, 1973). Lambert (1968) and Lambert (1978) gave a summary of all accessible atomic and molecular signatures of carbon, nitrogen, and oxygen, identifying the best ones to measure abundances. ...
Due to their production sites, as well as to how they are processed and destroyed in stars, the light elements are excellent tools to investigate a number of crucial issues in modern astrophysics: from stellar structure and non-standard processes at work in stellar interiors to age dating of stars; from pre-main sequence evolution to the star formation histories of young clusters and associations and to multiple populations in globular clusters; from Big Bang nucleosynthesis to the formation and chemical enrichment history of the Milky Way Galaxy and its populations, just to cite some relevant examples. In this paper, we focus on lithium, beryllium, and boron (LiBeB) and on carbon, nitrogen, and oxygen (CNO). LiBeB are rare elements, with negligible abundances with respect to hydrogen; on the contrary, CNO are among the most abundant elements in the Universe, after H and He. Pioneering observations of light-element surface abundances in stars started almost 70 years ago and huge progress has been achieved since then. Indeed, for different reasons, precise measurements of LiBeB and CNO are difficult, even in our Sun; however, the advent of state-of-the-art ground- and space-based instrumentation has allowed the determination of high-quality abundances in stars of different type, belonging to different Galactic populations, from metal-poor halo stars to young stars in the solar vicinity and from massive stars to cool dwarfs and giants. Noticeably, the recent large spectroscopic surveys performed with multifiber spectrographs have yielded detailed and homogeneous information on the abundances of Li and CNO for statistically significant samples of stars; this has allowed us to obtain new results and insights and, at the same time, raise new questions and challenges. A complete understanding of the light-element patterns and evolution in the Universe has not been still achieved. Perspectives for further progress will open up soon thanks to the new generation instrumentation that is under development and will come online in the coming years.
... Inspired by these works, more precise ★ E-mail: ramstojh@usp.br abundance compilations were put together, taking into account not only elements from meteorites, but also from the solar photosphere (e.g., Cameron 1973;Anders & Grevesse 1989;Grevesse & Sauval 1998;Lodders 2003;Asplund et al. 2005;Lodders et al. 2009;Asplund et al. 2009). All these results only confirm that the odd-even effect is real in the Sun, thereby suggesting that the proto-cloud of the Sun has this nucleosynthetic signature. ...
The abundance patterns observed in the Sun and in metal-poor stars show a clear odd-even effect. An important question is whether the odd-even effect in solar-metallicity stars is similar to the Sun, or if there are variations that can tell us about different chemical enrichment histories. In this work, we report for the first time observational evidence of a differential odd-even effect in the solar twin HIP 11915, relative to the solar odd-even abundance pattern. The spectra of this star were obtained with high resolving power (140 000) and signal-to-noise ratio ($\sim$420) using the ESPRESSO spectrograph and the VLT telescope. Thanks to the high spectral quality, we obtained extremely precise stellar parameters ($\sigma(T_{\rm eff})$ = 2 K, $\sigma(\rm{[Fe/H]})$ = 0.003 dex, and $\sigma(\log g)$ = 0.008 dex). We determine the chemical abundance of 20 elements ($Z\leq39$) with high precision ($\sim$0.01 dex), which shows a strong pattern of the odd-even effect even after performing Galactic Chemical Evolution corrections. The odd-even effect is reasonably well-reproduced by a core-collapse supernova of 13 $\rm{M_{\odot}}$ and metallicity Z = 0.001 diluted into a metal-poor gas of 1 $\rm{M_{\odot}}$. Our results indicate that HIP 11915 has an odd-even effect slightly different than the Sun, thus confirming a different supernova enrichment history.
... The solar abundances of neutron-capture elements require both the s-process and r-process (e.g., Cameron 1973). Observations of neutron-capture elements in nearby metal-poor stars have revealed both cases of universality, where the elemental abundance patterns of r-process rich stars are almost identical to that in the Sun (Sneden et al. 2008), and of diversity, where some stars show a deficiency of heavy r-process elements at A > ∼ 130, similar to the weak-r process pattern (Honda et al. 2004). ...
To reach a deeper understanding of the origin of elements in the periodic table, we construct Galactic chemical evolution (GCE) models for all stable elements from C (A=12) to U (A=238) from first principles, i.e., using theoretical nucleosynthesis yields and event rates of all chemical enrichment sources. This enables us to predict the origin of elements as a function of time and environment. In the solar neighborhood, we find that stars with initial masses of M>30M_\odot can become failed supernovae if there is a significant contribution from hypernovae (HNe) at M~20-50M_\odot. The contribution to GCE from super asymptotic giant branch (AGB) stars (with M~8-10M_\odot at solar metallicity) is negligible, unless hybrid white dwarfs from low-mass super-AGB stars explode as so-called Type Iax supernovae, or high-mass super-AGB stars explode as electron-capture supernovae (ECSNe). Among neutron-capture elements, the observed abundances of the second (Ba) and third (Pb) peak elements are well reproduced with our updated yields of the slow neutron-capture process (s-process) from AGB stars. The first peak elements, Sr, Y, and Zr, are sufficiently produced by ECSNe together with AGB stars. Neutron star mergers can produce rapid neutron-capture process (r-process) elements up to Th and U, but the timescales are too long to explain observations at low metallicities. The observed evolutionary trends, such as for Eu, can well be explained if ~3% of 25-50 M_\odot hypernovae are magneto-rotational supernovae producing r-process elements. Along with the solar neighborhood, we also predict the evolutionary trends in the halo, bulge, and thick disk for future comparison with galactic archaeology surveys.
... Frequency Remijan et al., in prep.). The [propynethial]/[propynal] abundance ratios reported here are relatively large (<0.1-17) compared to the solar sulfurto-oxygen ratio of ∼0.02 (Cameron 1973). The largest factor contributing to the non-detection is certainly the abundance of propynethial and the associated formation and destruction chemistry. ...
Context. The majority of sulfur-containing molecules detected in the interstellar medium (ISM) are analogs of oxygen-containing compounds. Propynal was detected in the ISM in 1988, hence propynethial, its sulfur derivative, is a good target for an ISM search.
Aims. Our aim is to measure the rotational spectrum of propynethial and use those measurements to search for this species in the ISM. To date, measurements of the rotational spectra of propynethial have been limited to a small number or transitions below 52 GHz. The extrapolation of the prediction to lines in the milimeter-wave domain is inaccurate and does not provide data to permit an unambiguous detection.
Methods. The rotational spectrum was re-investigated up to 630 GHz. Using the new prediction lines of propynethial, as well as the related propynal, a variety of astronomical sources were searched, including star-forming regions and dark clouds.
Conclusions. A total of 3288 transitions were newly assigned and fit together with those from previous studies, reaching quantum numbers up to J = 107 and K a = 24. Watson’s symmetric top Hamiltonian in the I r representation was used for the analysis, because the molecule is very close to the prolate limit. The search for propynethial resulted in a non-detection; upper limits to the column density were derived in each source.
... In total, sulfur-containing species comprise ∼10% of the known molecular inventory of any size, whereas one-third of all molecules are oxygen-containing. Despite the lower interstellar abundance of sulfur relative to oxygen (Cameron 1973), the large disparity between the number of S-and O-bearing species is striking, and may indicate detections of large, sulfur-bearing species in space are simply limited by the lack of precise laboratory rest frequencies. ...
A longstanding problem in astrochemistry is the inability of many current models to account for missing sulfur content. Many relatively simple species that may be good candidates to sequester sulfur have not been measured experimentally at the high spectral resolution necessary to enable radioastronomical identification. On the basis of new laboratory data, we report searches for the rotational lines in the microwave, millimeter, and submillimeter regions of the sulfur-containing hydrocarbon HCCSH. This simple species would appear to be a promising candidate for detection in space owing to the large dipole moment along its b-inertial axis, and because the bimolecular reaction between two highly abundant astronomical fragments (CCH and SH radicals) may be rapid. An inspection of multiple line surveys from the centimeter to the far-infrared toward a range of sources from dark clouds to high-mass star-forming regions, however, resulted in nondetections. An analogous search for the lowest-energy isomer, H_2CCS, is presented for comparison, and also resulted in nondetections. Typical upper limits on the abundance of both species relative to hydrogen are 10^(−9)–10^(−10). We thus conclude that neither isomer is a major reservoir of interstellar sulfur in the range of environments studied. Both species may still be viable candidates for detection in other environments or at higher frequencies, providing laboratory frequencies are available.
... In total, sulfur-containing species comprise ∼10% of the known molecular inventory of any size, whereas one-third of all molecules are oxygen-containing. Despite the lower interstellar abundance of sulfur relative to oxygen (Cameron 1973), the large disparity between the number of S-and O-bearing species is striking, and may indicate detections of large, sulfur-bearing species in space are simply limited by the lack of precise laboratory rest frequencies. ...
A longstanding problem in astrochemistry is the inability of many current models to account for missing sulfur content. Many relatively simple species that may be good candidates to sequester sulfur have not been measured experimentally at the high spectral resolution necessary to enable radioastronomical identification. On the basis of new laboratory data, we report searches for the rotational lines in the microwave, millimeter, and submillimeter regions of the sulfur-containing hydrocarbon HCCSH. This simple species would appear to be a promising candidate for detection in space owing to the large dipole moment along its b-inertial axis, and because the bimolecular reaction between two highly abundant astronomical fragments (CCH and SH radicals) may be rapid. An inspection of multiple line surveys from the centimeter to the far-infrared toward a range of sources from dark clouds to high-mass star-forming regions, however, resulted in nondetections. An analogous search for the lowest-energy isomer, H2CCS, is presented for comparison, and also resulted in nondetections. Typical upper limits on the abundance of both species relative to hydrogen are 1E-9 to 1E-10. We thus conclude that neither isomer is a major reservoir of interstellar sulfur in the range of environments studied. Both species may still be viable candidates for detection in other environments or at higher frequencies, providing laboratory frequencies are available.
... On Earth, 40 Ar is 300 times more abundant than 36 Ar (Lee et al. 2006), and as no signal from 40 ArH + was visible, 36 ArH + seemed to be an unlikely carrier. Barlow et al. (2013), however, recognized that 36 Ar is the dominant isotope in the ISM (Cameron 1973), and identified the J=1→0 and 2 1 rotational lines of 36 ArH + at 617.5 and 1234.6 GHz, respectively, in Herschel/SPIRE spectra of the Crab Nebula. A citation is only given for the CDMS database, as no laboratory data appear to exist for 36 ArH + . ...
To date, 204 individual molecular species, comprised of 16 different elements, have been detected in the interstellar and circumstellar medium by astronomical observations. These molecules range in size from 2 atoms to 70, and have been detected across the electromagnetic spectrum from centimeter wavelengths to the ultraviolet. This census presents a summary of the first detection of each molecular species, including the observational facility, wavelength range, transitions, and enabling laboratory spectroscopic work, as well as listing tentative and disputed detections. Tables of molecules detected in interstellar ices, external galaxies, protoplanetary disks, and exoplanetary atmospheres are provided. A number of visual representations of these aggregate data are presented and briefly discussed in context.
... Das Element Kohlenstoff stellt als vierthäufigstes Element auf der Erde den Grundstoff allen organischen Lebens dar. [49] Kohlenstoff ist durch eine besondere Bindungsvielfalt charakterisiert, die auf der Elektronenkonfiguration [He] 2s 2 2p 2 basiert und dem Element eine stark ausgeprägte Tendenz zu Hybridisierungen verleiht. [50] Kohlenstoff besitzt die Fähigkeit zum Aufbau verschiedenster organischer Moleküle bis hin zu komplexen, mehrdimensionalen Polymeren, was sich auch in den Allotropen (a) Fulleren, (b) Kohlenstoffnanoröhren (engl. ...
Die vorliegende Arbeit befasst sich mit der mechanochemischen Darstellung einer neuen Klasse von multifunktionalen Kohlenstoff-Nanofüllstoffen sowie deren Verwendung für die Herstellung neuartiger Kohlenstoff / Polymer-Hybridmaterialien und polymerer Nanokomposite mit unkonventionellen Eigenschaftskombinationen von Matrixverstärkung, Stabilität, Schadenstoleranz und Flammschutz.
Für die Darstellung von mechanochemisch funktionalisiertem Mehrlagengraphen (MG) als Nanofüllstoff wurde ein einfaches und effektives Mahlverfahren entwickelt. Natürlicher Graphit wurde dabei in einer Planetenkugelmühle unter Kohlenstoffdioxid-, Argon- und Ammoniakdruck und im Vakuum sowie in Gegenwart von rotem Phosphor (Prot) vermahlen, um Graphit zu exfolieren und gleichzeitig zu funktionalisieren. Dieser Ansatz erfordert keine Lösungsmittel und Nachbehandlungen, die ansonsten für zahlreiche, konventionelle Syntheseverfahren typisch sind. Insbesondere wurde durch den Einsatz von Mahlbehältern und Mahlgut aus abriebfester Keramik sowohl Metallabrieb als auch die bislang übliche Aufreinigung durch Nachbehandlung mit Säure eliminiert. Die Einflüsse von Verfahrensparametern wie Gasatmosphäre (CO2, Ar, Luft, NH3), Gasdruck bzw. Vakuum, Zusatz von Prot, Variation der Mahldauer (12 h, 18 h, 24 h, 48 h, 72 h) sowie ein- und zweistufige Funktionalisierung auf die Morphologie, Funktionalisierungsgrad, spezifische Oberfläche und elektrische Leitfähigkeit von MG wurden aufgeklärt. Mittels Raman-Spektroskopie wurde ein Zusammenhang zwischen der Exfolierung von Graphit und dem Druck in der Mahlkammer gefunden. Mechanochemisch wurden carboxyl-, hydroxyl- und aminfunktionalisiertes MG sowie mit Polyphosphorsäure und Ammoniumpolyphosphat gepfropfte MG-Nanofüllstoffe zugänglich gemacht. Die erfolgreiche Funktionalisierung wurde mittels FT-IR- und XPS-Spektroskopie nachgewiesen. Durch Schmelzcompoundierung sowie Reaktionsextrusion im Zweischnecken-Extruder gelang es bis zu 40 Gew.-% an MG in technischen Thermoplasten wie Polypropylen (PP) und Acrylnitril-Butadien-Styrol-Copolymeren (ABS) agglomeratfrei zu dispergieren und die so erhaltenen MG / Polymer-Nanokomposite durch Spritzguss zu verarbeiten. Aufgrund der erfolgreiche Funktionalisierung der MG war der sonst übliche Zusatz von Phasenvermittlern und Dispergierhilfsmittel dazu nicht erforderlich. Durch die Charakterisierung der morphologischen (TEM, SEM), thermischen (DSC, DMA) und mechanischen (Zugprüfung, DMA, Schlagpendel) Eigenschaften konnte aufgezeigt werden, dass der Zusatz von MG die Bilanz von Steifigkeit, Festigkeit und Schlagzähigkeit deutlich verbessert. Aminfunktionalisiertes MG konnte durch Reaktionsextrusion kovalent mit maleiniertem Polypropylen über Imdigruppen verknüpft werden. Durch die Pfropfung gelang es den E-Modul der PP / MG-Komposite zu steigern, ohne die bislang üblichen massiven Verluste an Bruchdehnung in Kauf nehmen zu müssen. Bei der Umsetzung von Graphit mit Prot konnte bei Kontakt mit Luft die Bildung von Polyphosphorsäuren und deren kovalente Anbindung an Hydroxylgruppen der MG nachgewiesen werden. Durch den Zusatz von 40 Gew.-% an Polyphosphorsäure bzw. Ammoniumpolyphosphat gepfropftem MG konnte der Brandschutz (V-0 Klassifizierung nach UL-94) des brennbaren PPs erheblich verbessert und das Abtropfen brennender PP-Tröpfchen verhindert werden. Die Einflüsse der Funktionalisierung und Morphologie der MGs auf die morphologischen, thermischen und mechanischen Eigenschaften sowie das Brandverhalten wurden im Rahmen dieser Arbeit aufgeklärt.
... Fluorine was produced via nucleosynthetic processes in stars, which predate the solar system [6]. Specifically, fluorine, with a single mass 19 9 F was produced through neutrino spallation of 20 Ne and cascade reactions of hydrogenehelium burning involving 14 N, 18 F, 18 O, and 15 N [7]. ...
This review (1) presents a summary of the distribution of fluorine in different fluid (surficial, subterranean, metamorphic, and magmatic–hydrothermal–geothermal) and solid (oceanic and continental crust, mantle, and core) domains of the Earth, and various extraterrestrial materials and bodies (meteorites, planets and moons, and the Sun); (2) it provides an estimate of the total fluorine abundance for the Earth and in its dominant reservoirs contributing to the Earth's fluorine endowment; and (3) it discusses key observations that could further improve our understanding of fluorine abundances and geochemical systematics.
The noble gases He and Ar occur as trace components in natural gas. Although their genesis is significantly different from that of hydrocarbon gases, they can provide key information on the accumulation and preservation of natural gas. For this paper, the relative and absolute abundances of He and Ar in lower Paleozoic shale gas samples from different areas of southern China were systematically analyzed, and the relationships between the concentrations of noble gases and the accumulation and expulsion of shale gas were evaluated. The evolution of He and Ar concentrations in shale gas system can be divided into three phases: the early accumulation stage, the hydrocarbon dilution stage and the preservation and enrichment stage. The generation of a large amounts of methane in the shale leads to the lowest relative concentrations of He and Ar in the hydrocarbon dilution stage. After that, the tectonic uplift causes the partial loss of the shale gas, and methane is no longer generated, but He and Ar are still produced. The concentrations of He and Ar present in shale gas are mainly controlled by the conditions of the preservation and enrichment stage. Tectonic uplift is the main reason for the loss of shale gas, and later uplift often results in higher gas content, which also leads to relatively low concentrations of He and Ar. The absolute abundance of residual Aratm and the He/Ar ratio of a shale gas can indirectly reflect the preservation conditions of that shale gas.
The interstellar chemistry of nitrogen is considerably less understood than the chemistry of other common elements, such as carbon and oxygen. Even though a relatively large number of species containing nitrogen atoms have already been detected in the interstellar medium, only six of them bear a nitrogen–oxygen (N–O) bond. Some astrophysical and primeval Earth models suggest that N–O species, such as hydroxylamine (NH2OH), are potential precursors of prebiotic amino acids, and even peptides. In this work, we have analyzed an apolar ice mixture of N2:CO of astrophysical interest to investigate possible formation mechanisms of N–O bearing molecules due to processing of the sample by 64Ni24+ 538 MeV ions (8.4 MeV/u) at 14 K. The results show the formation of simple nitrogen oxides ($\rm {N_{1 - 2}}{O_y})$, but no CN–O species of any kind. We have also determined the formation cross-sections of some of the products, as well as the destruction cross-sections of precursors and products. The results presented here are discussed in light of our previous work on the processing of a NH3:CO ice mixture, which have found no N–O bearing molecules at all.
The dual crisis of climate change and fossil fuel depletion has led to the search for a clean, environmentally sustainable, and globally available fuel which is also able to meet the surging energy demand. Hydrogen is one such element that could fulfill all these criteria. However, the major source of hydrogen generated today globally (approximately 95%) is fossil fuel and carbon oxides, including CO2, a greenhouse gas (GHG) are generated in the process. Other methods of H2 production from renewable sources such as water and biomass, although they are environmentally sustainable, are cost-intensive and/or operate at H2 production efficiencies lower than with methods based on conventional fossil fuel sources (60%–85%). Therefore, development of technologies for capture and storage of the CO2 by-product in the case of fossil fuel generated H2, upgrading the production efficiency of methods employing renewable sources for H2 production, and applying waste biorefinery concepts are the key challenges of the H2 fuel-based circular bioeconomy today. The present chapter gives a brief account of these concepts and their associated challenges.
Hydrogenases are multimeric metalloenzymes that are able to catalyze the reversible reaction of proton reduction to molecular hydrogen. These enzymes have been already used for small-scale hydrogen bioproduction. However, scaling up this process for industrial application requires genetic engineering of hydrogenases to improve their stability, as well as to develop a streamlined strategy for their production. The following article provides information on the structure, classification and applications of hydrogenases.
CO2 degassing of mafic silicate melts is an important part of the terrestrial carbon cycle, at mid-ocean ridges, oceanic hot spots, or in the middle of continents. Deeper CO2-bearing mafic magmas may also exist, such as those suspected in the D″ zone, and certainly existed in the magma ocean of the early Earth. Knowledge of the CO2 solubility in mafic melts at high pressure is therefore important but unknown at present. Results from molecular dynamics simulation (e.g., Guillot and Sator, 2011) predict that CO2 solubility in basalt may be much higher than previously thought at pressures and temperatures relevant to the upper mantle. But some recent models predict low solubility at high pressure (e.g., Eguchi and Dasgupta, 2018). The present study thus experimentally investigates the solubility of CO2 in basalt and andesite in the pressure range 1.5–8.5 GPa at 1820–2130 K in oxidizing conditions. Up to 4 GPa, the quenched samples are essentially vitreous and CO2-saturated. Their CO2 contents are measured using confocal micro-Raman spectroscopy, where we establish an internal calibration line relating CO2 content to the area of the Raman band assigned to the ν1 stretching vibration of carbonate groups. This calibration appears independent from the spectrometer, sample or experimentalist, thus enhancing confidence in this method. At 5 and 8.5 GPa, the quenched samples are found partially crystallized. Their CO2 abundance is estimated at micro-scale from Raman mapping, and at large scale from image analysis and presence/absence of vesicles. Over the 1.5–8.5 GPa pressure range, obtained CO2 concentrations vary between 1.8 and > 13.6 wt%. At 5 GPa and 1873 K, the CO2 content in basalt and andesite are similar. These findings experimentally confirm the ability of mafic melts to accommodate large amounts of CO2 at conditions prevailing in the deep Earth. A consequence is that magmas issued from partial melting of carbonate-bearing silicate rocks may ascend with significant quantities of CO2 of several wt% and more: when reaching shallower depths, they may degas large quantities of CO2. Present estimates of the global carbon flux to the atmosphere may thus be underestimated, and implications to early magma ocean degassing may be considered. Other consequences may concern the genesis of kimberlites and carbonatites. We finally speculate that, if silicate melts exist in the D″ zone, significant amounts of carbon may be stored there, and consequences may arise as to carbon sequestration in the core.
The chemical composition of the shell of a neutron star (SNS) at high temperatures and densities is discussed in this paper. A model for nucleosynthesis is proposed based on the approximation of nuclear statistical equilibrium (NSE). The dependence of the results of the nucleosynthesis on the parameters of the medium in a static approximation is studied. The results of this paper are qualitatively similar to earlier work by other authors. It is shown that the proposed model provides a fair description of the abundance of nuclei even in the static approximation.
Mars lacks a substantial magnetic field; as a result, the solar wind ablates the Martian atmosphere, and cosmic rays from solar flares make the surface uninhabitable. Therefore, any terraforming attempt will require an artificial Martian magnetic shield. The fundamental challenge of building an artificial magnetosphere is to condense planetary-scale currents and magnetic fields down to the smallest mass possible. Superconducting electromagnets offer a way to do this. However, the underlying physics of superconductors and electromagnets limits this concentration. Based upon these fundamental limitations, we show that the amount of superconducting material is proportional to $B_{\rm c}^{-2}a^{-3}$ , where B c is the critical magnetic field for the superconductor and a is the loop radius of a solenoid. Since B c is set by fundamental physics, the only truly adjustable parameter for the design is the loop radius; a larger loop radius minimizes the amount of superconducting material required. This non-intuitive result means that the ‘intuitive’ strategy of building a compact electromagnet and placing it between Mars and the Sun at the first Lagrange point is unfeasible. Considering reasonable limits on B c , the smallest possible loop radius is ~10 km, and the magnetic shield would have a mass of ~ 10 ¹⁹ g. Most high-temperature superconductors are constructed of rare elements; given solar system abundances, building a superconductor with ~ 10 ¹⁹ g would require mining a solar system body with several times 10 ²⁵ g; this is approximately 10% of Mars. We find that the most feasible design is to encircle Mars with a superconducting wire with a loop radius of ~3400 km. The resulting wire diameter can be as small as ~5 cm. With this design, the magnetic shield would have a mass of ~ 10 ¹² g and would require mining ~ 10 ¹⁸ g, or only 0.1% of Olympus Mons.
Decarboxylation strategy has been emerging as a powerful tool for the synthesis of fluorine-containing organic compounds that play important roles in various fields such as pharmaceuticals, agrochemicals, and materials science. Considerable progress in decarboxylation has been made over the past decade towards the construction of diverse valuable fluorinated fine chemicals for which the fluorinated part can be brought in two ways. The first way is described as the reaction of non-fluorinated carboxylic acids (and their derivatives) with fluorinating reagents, as well as fluorine-containing building blocks. The second way is dedicated to the exploration and the use of fluorine-containing carboxylic acids (and their derivatives) in decarboxylative transformations. This review aims to provide a comprehensive summary of the development and applications of decarboxylative radical, nucleophilic and cross-coupling strategies in organofluorine chemistry.
The abundance patterns observed in the Sun and in metal-poor stars show a clear odd-even effect. An important question is whether the odd-even effect in solar-metallicity stars is similar to the Sun, or if there are variations that can tell us about different chemical enrichment histories. In this work, we report for the first time observational evidence of a differential odd-even effect in the solar twin HIP 11915, relative to the solar odd-even abundance pattern. The spectra of this star were obtained with high-resolving power (140 000) and signal-to-noise ratio (∼420) using the ESPRESSO spectrograph and the VLT telescope. Thanks to the high spectral quality, we obtained extremely precise stellar parameters (σ(Teff) = 2 K, $\sigma (\rm {[Fe/H]})$ = 0.003 dex, and σ(log g) = 0.008 dex). We determine the chemical abundance of 20 elements (Z ≤ 39) with high precision (∼0.01 dex), which shows a strong pattern of the odd-even effect even after performing galactic chemical evolution corrections. The odd-even effect is reasonably well-reproduced by a core-collapse supernova of 13 $\rm {M_{\odot }}$ and metallicity Z = 0.001 diluted into a metal-poor gas of 1 $\rm {M_{\odot }}$. Our results indicate that HIP 11915 has an odd-even effect slightly different than the Sun, thus confirming a different supernova enrichment history.
Chlorine is a minor element present in obsidians in quantities greater than in average igneous rocks. The chlorine concentration in obsidians is generally low, of the order of tenths of wt %, but it exhibits an appreciable differentiation among geological sources. Despite these characteristics, chlorine has rarely been taken into consideration as a possible indicator of obsidian provenance and it does not appear in the chemical analytical tables accompanying the geochemical characterisation of obsidian samples.
In this work, after an overview of chlorine geochemistry and cycle, we present thirty-one new electron microprobe (EPMA) analyses, including Cl, of geologic obsidians sampled from the four sources of the Central Mediterranean, exploited in prehistoric times (Monte Arci, Palmarola, Lipari and Pantelleria). The results are compared with 175 new EPMA analyses, including Cl, of archaeological obsidians already characterised in previous work and of known provenance. As such it was possible to ascertain that each source has a characteristic chlorine concentration, showing the utility of its use in the studies of obsidian provenance. Furthermore, given that the solubility of chlorine in silicate melts is correlated to its alkali content, in particular sodium, we assessed the efficacy of simple binary graphs Cl vs Na 2 O to better constrain the provenance of the obsidian samples.
The chemistry of fluorinated compounds was essentially established by humans. Yet, fluorinated molecules have been present in our daily lives for a long time, be it as a nonstick coating for pans or as liquid crystals that are used in every smartphone, or as an important component of herbicides, pesticides, and pharmaceuticals. However these compounds are also released into nature and interact with plants and bacteria. Little is known about how nature adapts to increasing exposure to fluorinated molecules. In this chapter we want to shed light on the paths that fluorine takes in the ecosphere. We will discuss what nature does with these molecules and how nature itself produces fluorinated molecules. This is important in the context of the development of sustainable concepts in chemistry in order to conserve resources and tackle climate change.
To reach a deeper understanding of the origin of elements in the periodic table, we construct Galactic chemical evolution (GCE) models for all stable elements from C ( A = 12) to U ( A = 238) from first principles, i.e., using theoretical nucleosynthesis yields and event rates of all chemical enrichment sources. This enables us to predict the origin of elements as a function of time and environment. In the solar neighborhood, we find that stars with initial masses of M > 30 M ⊙ can become failed supernovae if there is a significant contribution from hypernovae (HNe) at M ∼ 20–50 M ⊙ . The contribution to GCE from super-asymptotic giant branch (AGB) stars (with M ∼ 8–10 M ⊙ at solar metallicity) is negligible, unless hybrid white dwarfs from low-mass super-AGB stars explode as so-called Type Iax supernovae, or high-mass super-AGB stars explode as electron-capture supernovae (ECSNe). Among neutron-capture elements, the observed abundances of the second (Ba) and third (Pb) peak elements are well reproduced with our updated yields of the slow neutron-capture process (s-process) from AGB stars. The first peak elements (Sr, Y, Zr) are sufficiently produced by ECSNe together with AGB stars. Neutron star mergers can produce rapid neutron-capture process (r-process) elements up to Th and U, but the timescales are too long to explain observations at low metallicities. The observed evolutionary trends, such as for Eu, can well be explained if ∼3% of 25–50 M ⊙ HNe are magneto-rotational supernovae producing r-process elements. Along with the solar neighborhood, we also predict the evolutionary trends in the halo, bulge, and thick disk for future comparison with Galactic archeology surveys.
Mendeleev’s introduction of the periodic table of elements is one of the most important milestones in the history of chemistry, as it brought order into the known chemical and physical behaviour of the elements. The periodic table can be seen as parallel to the Standard Model in particle physics, in which the elementary particles known today can be ordered according to their intrinsic properties. The underlying fundamental theory to describe the interactions between particles comes from quantum theory or, more specifically, from quantum field theory and its inherent symmetries. In the periodic table, the elements are placed into a certain period and group based on electronic configurations that originate from the Pauli and Aufbau principles for the electrons surrounding a positively charged nucleus. This order enables us to approximately predict the chemical and physical properties of elements. Apparent anomalies can arise from relativistic effects, partial-screening phenomena (of type lanthanide contraction) and the compact size of the first shell of every l-value. Further, ambiguities in electron configurations and the breakdown of assigning a dominant configuration, owing to configuration mixing and dense spectra for the heaviest elements in the periodic table. For the short-lived transactinides, the nuclear stability becomes an important factor in chemical studies. Nuclear stability, decay rates, spectra and reaction cross sections are also important for predicting the astrophysical origin of the elements, including the production of the heavy elements beyond iron in supernova explosions or neutron-star mergers. In this Perspective, we critically analyse the periodic table of elements and the current status of theoretical predictions and origins for the heaviest elements, which combine both quantum chemistry and physics.
Water, methane, and ammonia are commonly considered to be the key components of the interiors of Uranus and Neptune. Modelling the planets’ internal structure, evolution, and dynamo heavily relies on the properties of the complex mixtures with uncertain exact composition in their deep interiors. Therefore, characterising icy mixtures with varying composition at planetary conditions of several hundred gigapascal and a few thousand Kelvin is crucial to improve our understanding of the ice giants. In this work, pure water, a water-ethanol mixture, and a water-ethanol-ammonia “synthetic planetary mixture” (SPM) have been compressed through laser-driven decaying shocks along their principal Hugoniot curves up to 270, 280, and 260 GPa, respectively. Measured temperatures spanned from 4000 to 25000 K, just above the coldest predicted adiabatic Uranus and Neptune profiles (3000–4000 K) but more similar to those predicted by more recent models including a thermal boundary layer (7000–14000 K). The experiments were performed at the GEKKO XII and LULI2000 laser facilities using standard optical diagnostics (Doppler velocimetry and optical pyrometry) to measure the thermodynamic state and the shock-front reflectivity at two different wavelengths. The results show that water and the mixtures undergo a similar compression path under single shock loading in agreement with Density Functional Theory Molecular Dynamics (DFT-MD) calculations using the Linear Mixing Approximation (LMA). On the contrary, their shock-front reflectivities behave differently by what concerns both the onset pressures and the saturation values, with possible impact on planetary dynamos.
Both the fundamental constants that describe the laws of physics and the cosmological parameters that determine the properties of our universe must fall within a range of values in order for the cosmos to develop astrophysical structures and ultimately support life. This paper reviews the current constraints on these quantities. The discussion starts with an assessment of the parameters that are allowed to vary. The standard model of particle physics contains both coupling constants (α,α s ,α w ) and particle masses (m u ,m d ,m e ), and the allowed ranges of these parameters are discussed first. We then consider cosmological parameters, including the total energy density of the universe (Ω), the contribution from vacuum energy (ρ Λ ), the baryon-to-photon ratio (η), the dark matter contribution (δ), and the amplitude of primordial density fluctuations (Q). These quantities are constrained by the requirements that the universe lives for a sufficiently long time, emerges from the epoch of Big Bang Nucleosynthesis with an acceptable chemical composition, and can successfully produce large scale structures such as galaxies. On smaller scales, stars and planets must be able to form and function. The stars must be sufficiently long-lived, have high enough surface temperatures, and have smaller masses than their host galaxies. The planets must be massive enough to hold onto an atmosphere, yet small enough to remain non-degenerate, and contain enough particles to support a biosphere of sufficient complexity. These requirements place constraints on the gravitational structure constant (α G ), the fine structure constant (α), and composite parameters (C ⋆ ) that specify nuclear reaction rates. We then consider specific instances of possible fine-tuning in stellar nucleosynthesis, including the triple alpha reaction that produces carbon, the case of unstable deuterium, and the possibility of stable diprotons. For all of the issues outlined above, viable universes exist over a range of parameter space, which is delineated herein. Finally, for universes with significantly different parameters, new types of astrophysical processes can generate energy and thereby support habitability.
Saturn formed beyond the snow line in the primordial solar nebula, and that made it possible for it to accrete a large mass. Disk instability and core accretion models have been proposed for Saturn’s formation, but core accretion is favored on the basis of its volatile abundances, internal structure, hydrodynamic models, chemical characteristics of protoplanetary disk, etc. The observed frequency, properties, and models of exoplanets provide additional supporting evidence for core accretion. The heavy elements with mass greater than 4He make up the core of Saturn, but are presently poorly constrained, except for carbon. The C/H ratio is super-solar, and twice that in Jupiter. The enrichment of carbon and other heavy elements in Saturn and Jupiter requires special delivery mechanisms for volatiles to these planets. In this chapter we will review our current understanding of the origin and evolution of Saturn and its atmosphere, using a multi-faceted approach that combines diverse sets of observations on volatile composition and abundances, relevant properties of the moons and rings, comparison with the other gas giant planet, Jupiter, and analogies to the extrasolar giant planets, as well as pertinent theoretical models.
Motivated by the possible existence of other universes, this paper considers the evolution of massive stars with different values for the fundamental constants. We focus on variations in the triple alpha resonance energy and study its effects on the resulting abundances of ¹²C, ¹⁶O, and larger nuclei. In our universe, the 0⁺ energy level of carbon supports a resonant nuclear reaction that dominates carbon synthesis in stellar cores and accounts for the observed cosmic abundances. Here we define ΔER to be the change in this resonant energy level, and show how different values affect the cosmic abundances of the intermediate alpha elements. Using the state of the art computational package MESA, we carry out stellar evolution calculations for massive stars in the range M* = 15−40M⊙, and for a wide range of resonance energies. We also include both solar and low metallicity initial conditions. For negative ΔER, carbon yields are increased relative to standard stellar models, and such universes remain viable as long as the production of carbon nuclei remains energetically favorable, and stars remain stable, down to ΔER≈−300 keV. For positive ΔER, carbon yields decrease, but significant abundances can be produced for resonance energy increments up to ΔER≈+500 keV. Oxygen yields tend to be anti-correlated with those of carbon, and the allowed range in ΔER is somewhat smaller. We also present yields for neon, magnesium, and silicon. With updated stellar evolution models and a more comprehensive survey of parameter space, these results indicate that the range of viable universes is larger than suggested by earlier studies.
The article gives a concise overview of solar dynamical processes and their impacts on the space weather. This article is based on the observational and theoretical developments made during last few decades. The article begins with a brief discussion of the Sun and the solar interior, from the core to the solar corona. We discuss the solar magnetic field and provide some basic understanding of the solar dynamo model. The solar dynamical processes, the transient as well as the gradual, are the manifestations of the Sun’s magnetic field. Magnetic reconnection, as well as submergence and emergence of magnetic flux tubes, plays an important role in the solar activities. This article tries to cover a range of dynamical processes, including sunspots, solar prominences and bright points. We also discussed various models of the dynamical processes along with their properties and effect on other activities occurring on the Sun.
New methods for preparation of tailor-made fluorine-containing compounds are in extremely high demand in nearly every sector of chemical industry. The asymmetric construction of quaternary C-F stereogenic centers is the most synthetically challenging and, consequently, the least developed area of research. As a reflection of this apparent methodological deficit, pharmaceutical drugs featuring C-F stereogenic centers constitute less than 1% of all fluorine-containing medicines currently on the market or in clinical development. Here we provide a comprehensive review of current research activity in this area, including such general directions as asymmetric electrophilic fluorination via organocatalytic and transition-metal catalyzed reactions, asymmetric elaboration of fluorine-containing substrates via alkylations, Mannich, Michael, and aldol additions, cross-coupling reactions, and biocatalytic approaches.
Die in der ersten Mitteilung ¹ durch die Anwendung plausibler Häufigkeitsregeln vorgenommenen Ausgleichungen der Goldschmidtschen Werte² für die kosmischen Häufigkeiten der Elemente zeigen, daß der durchschnittliche Gehalt der Meteoriten an Se, Te, Ga, In, Tl, Zn, Cd, Hg und Re bedeutend geringer ist als der kosmischen Häufigkeit dieser Elemente entsprechen würde. Die neue Häufigkeitsverteilung läßt die häufig-keitsmäßige Bevorzugung der Kerne mit bestimmten Protonen-und Neutronenzahlen besonders deutlich erkennen. Eine ähnliche, wenn auch weit weniger augenfällige Bevorzugung scheint auch bei bestimmten Neutronenüberschußwerten vorzuliegen.
From observations of the nu 2 parallel band of mono-deuterated methane (CH3D) in the Jovian atmosphere, we have deduced a CH3D abundance and mixing ratio and a value for the D/H ratio in this planet, with due regard to the problems of Jovian atmospheric structure and deuterium fractionation. We find the D/H ratio to be significantly less than the terrestrial value and discuss some of the implications to the early history of the solar system. This observation marks the first-ever detection of deuterium by any astronomical technique.
Gas rich meteorites and lunar materials solar rare gases component observed and predicted relative abundance agreement indicating absence of fractionation in solar nebula formation
Measurement of the charge composition for several of the multicharged nuclei and the energy spectra for hydrogen, helium, and medium (6 less than or equal to Z less than or equal to 9) nuclei in the Apr. 12, 1969, solar-particle event. The energy/nucleon spectral shape of the medium nuclei was again the same as that of the helium nuclei, and the ratio of these two species was consistent with the present best average of 58 plus or minus 5. By combining the results obtained here with previous work, improved estimates of the Ne/O and Mg/O values of 0.16 plus or minus 0.03 and 0.056 plus or minus 0.014, respectively, were obtained. Silicon and sulfur abundances relative to O were determined to be 0.208 plus or minus 0.008 plus or minus 0.006, respectively, and 85% confidence upper limits for Ar and Ca relative to O of 0.017 and 0.010 were obtained. Previously, these last four nuclei had only been listed as a group.
This volume is intended to bring together in one convenient source the
extensive information about the abundances of the elements in meteoritic samples
and to give some indication of the relative quality of this data. There is one
chapter for each element which can be found in meteorites. (WDM)
The abundance of boron is of considerable interest, but is difficult to
determine. Boron undergoes thermonuclear destruction in stellar
interiors, and hence is not a normal product of stellar nucleosynthesis.
Thus its abundance is low, and until now it has seemed possible to
understand its production in nature as a consequence of cosmic ray
bombardment of the interstellar medium1. We point out here
that the cosmic abundance of boron has been greatly underestimated, and
that the upward revision of its abundance has important consequences in
several areas of astrophysics.
Five lines of evidence suggest that Cl chondrites closely approximate the condensable fraction of primordial solar-system matter: continuity of isotopic and elemental abundance trends, agreement with solar and cosmic-ray abundances, fractionation patterns among chondrites, and absence of chondrules. Maximum differences between Cl abundances and true solar-system abundances are estimated as factors of 2–5 for individual elements and a factor of 1.5 or less for groups of 10 or more elements.
A review of the sources of analytical data for the chondritic meteorites is given, and the latest data, particularly for the minor elements, are tabulated. Though the composition of the chondrites is remarkably constant as compared with terrestrial rocks, important variations in the concentrations of certain major and minor constituents occur, which make it impossible to conclude that any one type of chondrite could have been produced from another by simple physical processes. This is true for the carbonaceous, enstatitic, and the high- and low-iron-group chondrites. The origin of these chondrites is discussed mostly with reference to the author’s suggestions about the origin of the solar system. Only very complicated processes can account for the detailed characteristics of these objects. The possibility that the carbonaceous chondrites and particularly Wiik's type 1 of this group are the primitive material from which the meteorites and planets originated is considered, and it is concluded that these objects as a group cannot be such material (a conclusion reached by the author some ten years ago). The case for the type 1 carbonaceous chondrites' being this material is better, but serious arguments against this conclusion can be advanced; it is concluded that even this material has undergone some extensive chemical processing.
Some energy levels of Sr 87 shows hyperfine splitting which broadens strontium lines in the solar spectrum. By analysis of two faint photospheric Sr i lines of Multiplet No. 3 an upper limit of the relative Sr 87 content (Sr 87/Sr) of 1/4 has been found. The terrestrial value is 0.07–0.075.
The solar abundance of strontium found from the two lines is log ɛ
Sr = 2.90 in the log ɛ
H = 12.00 scale. Using the solar rubidium abundance recently determined by the author (Hauge, 1972), one obtains ɛ
Rb/ɛ
Sr = 0.5±0.1. This value is larger than found even in chondrites showing high rubidium content.
Zirconium and hafnium have been determined in 28 chondrites and 7 achondritea by the use of thermal and 14 MeV neutron activation analyses. The distribution pattern of these elements in the three major classes of chondrites showed that the order of atomic abundances for both elements relative to silicon (Si = 10 6 atoms) was: carbonaceous chondrites > ordinary chondrites > enstatite chondrites. Average atomic abundances of 13 atoms Zr (Si = 10 6 atoms) and 0.19 atom Hf (Si = 10 6 atoms) were established for the chondrites. The calcium-rich achondrites were observed to be enriched in these elements relative to the chondrites while an opposite trend was noted for the calcium-poor achondrites. The average Zr/Hf ratio on a weight basis for all the stony meteorites analyzed in this work was 43, a value which is in good agreement with that reported in the literature for the earth's crust. Based on this ratio, no significant fractionation of these elements between the earth and meteorites is implied.
Notes for a series of lectures on stellar evolution, nuclear astrophysics, and nucleogenesis are presented. Topics covered include galaxy development, nuclear and thermonuclear reactions (particularly heavy-ion, helium, and hydrogen reactions), reaction rates, stellar evolution, abundances of elements and nuclides, stellar evolution, supernova explosions, neutron capture, physical conditions in stellar interiors, and the Hertzsprung-Russell diagrams. The lectures were intended to look at the development of different kinds of stars, the nuclear reactions which can go on in their interiors and the bearing of these considerations on the chemical composition of the universe and origin of the elements.
The present working values of the solar abundances of 65 chemical elements are listed. The abundance of some elements is based on one line only, and the results may be erroneous. A separate list is given showing isotope ratios of eight elements that have been investigated so far. (Author)
The origin of deuterium has always been a problem for theories of
stellar nucleosynthesis, A general solution is proposed and shown to be
applicable under several astrophysical circumstances in the light of new
observations of the Galactic abundance of deuterium.
Low noise, high resolution spectral scans have been obtained for the resonance lines of silver λ3280.7 and λ3382.9, observed at the centre of the solar disk. A double pass-monochromator is used in conjunction with the Snow telescope at Mount Wilson; the transparency of the sky is monitored during the observations in order to achieve required accuracy. The data are analyzed by the method of spectral synthesis wherein we employ a model atmosphere resembling Elste's (1968) model and checked by limb-darkening observations. The present kinematical model adopts a macroturbulent velocity of 2.2 km s−1 and no microturbulence. With this model line profiles can be reproduced without invoking implausibly large collisional damping constants.
The silver abundance turns out to be {Ag}=log[N(Ag)/N(H)]+12;=0.85, a factor of four under the value found from the Type I carbonaceous chondrites.
By multiplying by certain factors of correctionGoldschmidt's orUnsld's values for the relative abundance of the elements, a general and coherent picture of the abundance of nuclei can be derived showing that simple rules hold for the abundance of the different types of nuclei. From the fact, that these factors of correction are small and within the limits of error for the majority of the elements, it is to be concluded that the values given by these authors are not far from representing the relative amounts in which the elements originally have been formed. For a small number of elements a comparatively large correction ofGoldschmidt's values is needed, but these elements do nearly all belong to the same geochemical group, viz. that of the calcophile elements. Revised abundance values are tabled, including those for the rare gases. Two plots illustrate the general picture of nuclear abundance. Reference is made to the significance of this picture as a lead towards better theoretical understanding of the structure of the nuclei, and of the formation of the elements.
The Rb i resonance lines at 7800 and 7947 in the photospheric spectrum of the Sun have profiles which are influenced by the isotopic composition of rubidium. High resolution spectra obtained with the McMath Solar Telescope at Kitt Peak National Observatory have been studied. A solar isotopic composition Rb87/Rb = 0.270.04 was found using spectra of the Rb i line at 7800 obtained with the spectrograph slit in positions close to the solar limb. The other Rb i line was abandoned since it was seriously blended with a water vapour line and some additional faint unknown lines.
From 13 scans obtained with a double-band pass spectrograph at the Snow telescope at Mount Wilson, interpreted by the method of spectral synthesis, the abundance of gold turns out to be log [N(Au)/N(H)] + 12 = 0.70, assuming loggf = – 0.57.
A neutron activation analysis technique was used to determine Au, Re, Co, Mo, As, Sb, Ga, Se, Te, Hg, Zn, Bi and Tl in 11 carbonaceous chondrites, 12 unequilibrated ordinary chondrites (UOC), and 4 equilibrated ordinary chondrites. The first 6 elements are ‘undepleted’, the next 3 ‘normally-depleted’ and the last 4 ‘strongly-depleted’. Except for Hg, ‘depleted-element’ abundances in carbonaceous chondrites lead to mean relative ratios of C1:C2:C3 = 1.00:0.53:0.29, i.e. those predicted by a two-component (mixing of high-temperature and low-temperature fractions) model. The last 4 nominally ‘undepleted’ elements are somewhat depleted in ordinary chondrites, As and Sb showing partial depletion in C3 and the latter in C2 chondrites as well. This requires a modification of the two-component model to indicate that deposition of elements during condensation of high temperature material was not an all-or-nothing process.Apart from Bi and Tl, the elements studied have similar abundances in unequilibrated and equilibrated ordinary chondrites and only the former are unquestionably correlated with the degree of disequilibrium in silicate minerals. Only some ‘strongly-depleted’ elements exhibit at least one of the following—proportional depletion in UOC, progressive depletion in petrographic grades 3–6 ordinary chondrites and enrichment in the gas-containing dark portion of gas-rich, light-dark meteorites—indicating that such depletion does not ensure that an element will exhibit these trends. Partly or completely siderophile As, Au, Co, Ga, Mo, Re and Sb vary with chemical type in the same manner in both unequilibrated and equilibrated ordinary chondrites and doubtless reflect a process involving fractionation of metallic iron.
Seventeen trace elements (Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Rb, Re, Sb, Se, Te, Tl, U and Zn) were measured by neutron activation analysis in 8 C1 samples (1 Alais, 3 Ivuna, 4 Orgueil) and in 3 C2 samples (one each of Mighei, Murchison, Murray). The results show far less scatter than earlier literature data. The standard deviation of a single measurement from the mean of 8 C1 samples lies between 2 and 14 per cent, except for the following 4 elements: Au ±18 per cent, Ag ±22 per cent, Rb ±19 per cent and Br ±33 per cent. The first two probably reflect contamination and sample heterogeneity, the last two, analytical error. Apparently C1 chondrites have a far more uniform composition than some authors have claimed.The new data suggest significant revisions in cosmic abundance for the following elements (old values in parentheses): Zn 1250 (1500), Cd 1.51 (2.12), Ir 0.72 (0.43) atoms/106 Si atoms. The Br value is also lower, 6.8 vs 20.6, but may be affected by analytical error.Relative to C1 chondrites, the C2 chondrites Mighei, Murchison and Murray are depleted in volatile elements by a factor of 0.508 ± 0.038, much more constant than indicated by oldor data. Ordinary chondrites also show a more uniform depletion relative to the new C1 data. The mean depletion factor of Sb, F, Cu, Ga, Ge, Sn, S, Se, Te and Ag is 0.227 ± 0.027 in H-chondrites. This constancy further strengthens the case for the two-component model of chondrite formation.
Data are presented from stepwise heating experiments and total extractions on five meteorites: Kapoeta, Fayetteville, Holman Island, Cee Vee and Pultusk. These data reveal the presence of four isotopically distinct trapped neon components. A comparison of trapped neon with trapped helium and argon in bulk analyses indicates the existence of correlated helium, neon and argon isotopic structures. The major trapped components in gas-rich meteorites and the LFB (lunar fines and breccia) are found to have the following isotopic compositions Component B 3.9 ± 0.3 12.52 ± 0.18 0.0335 ± 0.0015 5.37 ± 0.12 Component C 4.1 ± 1.0 10.6 ± 0.3 0.042 ± 0.003 4.1 ± 0.8 Component D 1.5 ± 1.0 14.5 ± 1.0 − 6 ± 1 Component B is attributed primarily to direct implantation of rare gas ions by the present day solar wind. Component C is identified with directly implanted low energy (1–10 Mev/n) solar flare rare gases. Component D is associated with rare gas ions implanted in meteoritic material by the primitive, pre-main sequence, solar wind. A fourth component, observed only in Kapoeta and the LFB, is tentatively attributed to parent body ‘atmospheric’ ions implanted in surface material by a solar wind induced electric field.
Chainpur and similar, apparently primitive, chondritic meteorites may be precursors of ordinary chondrites; a variety of evidence
supports this working hypothesis. In general, carbonaceous chondrites seem to be related collaterally to this genetic sequence
rather than being direct ancestors of ordinary chondrites. Metamorphic processes may be responsible for fractionations of
elements such as indium and iodine, and type-II carbonaceous chondrites seem to be more primitive than types I or IIIA.
Abundances of Na, Al, Sc, Cr, Mn, Fe, Co and Cu have been measured by instrumental neutron activation analyses of 103 chondrites and 17 achondrites. In many cases, analyses were made of replicate samples from the same meteorite. Various sources of error in the method, including sampling errors, are discussed in detail. Examination of the patterns of coherence of the elements we have determined suggests that we can perceive effects of fractionation during condensation from the solar nebula of matter parental to chondrites. Such effects seem to be exhibited both in the abundances of lithophilic elements, perhaps being related to varied temperatures of accretion and in the abundances of those elements which would be affected by metal‐silicate fractionation in the solar nebula.
Atomic abundances relative to Si vary little in carbonaceous chondrites, suggesting that efficient mixing processes operated on these meteorites prior to or during their formation. We suggest that at present, no single class of carbonaceous chondrites is clearly more primitive than another. Carbonaceous and unequilibrated ordinary chondrites may represent aggregates of material accreted from the solar nebula at relatively low temperatures, as many recent discussions of these meteorites would suggest. Our data support a model of equilibration and minor mobilization of non‐volatile elements within small domains of chondrites after accretion. Such a model would be consistent with the petrologic types of Van Schmus and Wood (1967).
Achondrites do not exhibit simple regularities in lithophilic elemental abundances as do chondrites. Models for the origins of achondrites surely must include effects of magmatic fractionation, but we do not at present have enough information to assess the plausibility of such models.
Reported at the meeting of the Division of Planetary Sciences
- J T Trauger
- F L Roesler
- N P Carleton
- W A Traub