Grotzinger et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

The Curiosity rover discovered fine-grained sedimentary rocks, which are inferred to represent an ancient lake and preserve evidence of an environment that would have been suited to support a martian biosphere founded on chemolithoautotrophy. This aqueous environment was characterized by neutral pH, low salinity, and variable redox states of both iron and sulfur species. Carbon, hydrogen, oxygen, sulfur, nitrogen, and phosphorus were measured directly as key biogenic elements; by inference, phosphorus is assumed to have been available. The environment probably had a minimum duration of hundreds to tens of thousands of years. These results highlight the biological viability of fluvial-lacustrine environments in the post-Noachian history of Mars.

Reference
Grotzinger et al. (2014) A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars. Science vol. 343.
[doi:10.1126/science.1242777]
Reprinted with permission from AAAS

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John P. Grotzinger

Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.

Reference
Grotzinger JP (2014) Introduction: Habitability, Taphonomy, and the Search for Organic Carbon on Mars. Science 343:386-387.
[doi:10.1126/science.1249944]
Reprinted with permission from AAAS

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Humberto Campins and Christine M. Comfort

Department of Physics and Astronomy, University of Central Florida, Orlando, Florida 32816-2385, USA.

Reference
Campins H and Comfort CM (2014) Solar system: Evaporating asteroid. Nature 505:487–488.
[doi:10.1038/505487a]

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Küppers et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

Reference
Küppers et al. (2014) Localized sources of water vapour on the dwarf planet (1) Ceres. Nature 505:525–527.
[doi:10.1038/nature12918]

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R.K. Mishra and J.N. Goswami
Physical Research Laboratory, Navrangpura, Ahmedabad, 380009;India

The short-lived now-extinct nuclide ⁶⁰Fe, present in the early Solar System, is a unique product of stellar nucleosynthesis. Even though the first hint for its presence in the early Solar System was obtained more than two decades back, a robust value for Solar System Initial (SSI) ⁶⁰Fe/⁵⁶Fe is yet to be established. A combined study of ²⁶Al-²⁶Mg and ⁶⁰Fe-⁶⁰Ni isotope systematics in chondrules from unequilibrated ordinary chondrites of low petrologic type, Semarkona (LL3.0), LEW 86134 (L3.0), and Y 791324 (L3.1), has been conducted to infer the value of SSI ⁶⁰Fe/⁵⁶Fe. Seven of the analyzed chondrules host resolved radiogenic excess in both⁶⁰Ni and ²⁶Mg resulting from in situ decay of the short-lived nuclides ⁶⁰Fe and ²⁶Al, respectively. The initial²⁶Al/²⁷Al values for these chondrules range from (6.9± 5.8)× 10^-6 to (3.01±1.78) ×10^-5 that suggest their formation between 2.1 to 0.6 Ma after CAIs. The initial ⁶⁰Fe/⁵⁶Fe at the time of formation of these chondrules ranges from (3.2±1.3) ×10^-7 to (1.12±0.39) ×10^-6 and show a good correlation with their initial ²⁶Al/²⁷Al values suggesting co-injection of the two short-lived nuclides, ⁶⁰Fe and ²⁶Al, into the protosolar cloud from the same stellar source. Considering ²⁶Al as a reliable early Solar System chronometer, this data set yield a SSI⁶⁰Fe/⁵⁶Fe value of (7.0±1.2) ×10^-7, if we adopt a half-life value of 2.6 Ma for ⁶⁰Fe reported in a recent study. Model stellar nucleosynthesis yields suggest that both a high mass (5-6.5 M_⊙) Asymptotic Giant Branch (AGB) star or a supernova (SN) could be the source of ⁶⁰Fe and ²⁶Al present in the early solar system. A high mass (∼25M_⊙) SN appears more plausible because of the much higher probability of its close association with the protosolar molecular cloud than a high mass AGB star. Such a SN can also account for SSI abundance of²⁶Al and its correlated presence with ⁶⁰Fe in chondrules.

Reference
Mishra RK and Goswami JN (2014) Fe-Ni and Al-Mg isotope records in UOC chondrules: Plausible stellar source of 60Fe and other short-lived nuclides in the early Solar System. Geochimica et Cosmochimica Acta 167:956.
[doi:10.1016/j.gca.2014.01.011]

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John W. Valley, Michael J. Spicuzza and Takayuki Ushikubo

WiscSIMS, Department of Geoscience, University of Wisconsin, 1215 W. Dayton St., Madison, WI, 53706, USA

We currently seek a copyright agreement with Springer to display their abstracts.

Reference
Valley JW, Spicuzza MJ and Ushikubo T (2014) Correlated δ18O and [Ti] in lunar zircons: a terrestrial perspective for magma temperatures and water content on the Moon. Contributions to Mineralogy and Petrology 167:956.
[doi:10.1007/s00410-013-0956-4]

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Hiroshi Kimura

Graduate School of Science, Kobe University, c/o CPS (Center for Planetary Science), Chuo-ku Minatojima Minamimachi
7-1-48, Kobe 650-0047, Japan

We model dust in comets, protoplanetary disks, and debris disks as aggregates consisting of submicron-sized grains with a silicate core and an organic-rich carbonaceous mantle. By computing the infrared (IR) spectra of the aggregates, we show that the degree of carbonization determines the positions of infrared peaks characteristic of magnesium-rich crystalline silicates. We discuss our results in terms of processing of organic materials by ultraviolet irradiation, ion bombardments, and thermal devolatilization. A comparison between the model IR spectra of the aggregates and the observed spectra of dust in circumstellar disks reveals that at least one third of the organic refractory component has suffered from carbonization in a very short timescale.

Reference
Kimura H (in press) The Organic-Rich Carbonaceous Component of Dust Aggregates in Circumstellar Disks: Effects of Its Carbonization on Infrared Spectral Features of Its Magnesium-Rich Olivine Counterpart. Icarus
[doi:10.1016/j.icarus.2014.01.009]
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Romain Tartèse^a and Mahesh Anand^b

^aPlanetary and Space Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, United Kingdom
^bDepartment of Earth Sciences, The Natural History Museum, Cromwell Road, London, SW7 5BD, United Kingdom

Referes to
Romain Tartèse, Mahesh Anand
Late delivery of chondritic hydrogen into the lunar mantle: Insights from mare basalts
Earth and Planetary Science Letters, Volume 361, 1 January 2013, Pages 480-486

The authors regret for an error which was introduced in an intermediate step involved in calculating the amount of chondritic material added to the lunar interior to account for the estimated H content of the mare basalt source regions (Section 6, lines 12–25). The revised text is as follows:
Assuming a 400 km deep solidified mantle with 25 ppm H and a density of 3300 kg m⁻³ implies that∼1×10¹⁸ kg of H has been added by chondrite-type impactors and efficiently mixed in the upper lunar mantle. Taking the measured H content of ∼5000–15 000 ppm in CI chondrites (Alexander et al., 2012 and Kerridge, 1985), this represents a mass of about 6.2×10¹⁹ to 1.8×10²⁰ kg of CI-type material accreted to the lunar upper mantle. This corresponds to 0.2–0.5 wt.% of the 400 km deep upper mantle considered here. By comparison, HSE abundances in lunar basalts require an amount of ∼1.6×10¹⁹ kgof chondritic material to have been accreted and mixed into the lunar upper mantle (Bottke et al., 2010 and Day et al., 2007), around 8±4 times less than that required for a lunar mantle with 25 ppm H.

Reference
Tartèse R and Anand M (in press) Corrigendum to “Late delivery of chondritic hydrogen into the lunar mantle: Insights from mare basalts” [Earth Planet. Sci. Lett. 361 (2013) 480–486]. Earth and Planetary Science Letters
[doi:10.1016/j.epsl.2014.01.002]
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Sachiko Amari^a, Ernst Zinner^a, Roberto Gallino^b

^aMcDonnell Center for the Space Sciences and the Physics Department, Washington University, St. Louis, MO 63130, USA
^bDipartimento di Fisica, Università di Torino, I-10125 Torino, Italy

We studied presolar graphite grains from four density fractions, KE3 (1.65 – 1.72 g/cm³), KFA1 (2.05 – 2.10 g/cm³), KFB1 (2.10 – 2.15 g/cm³), and KFC1 (2.15 – 2.20 g/cm³), extracted from the Murchison (CM2) meteorite, with the ion microprobe. One of the most interesting features of presolar graphite is that isotopic features depend on density. There are grains with ¹⁵N and ¹⁸O excesses, Si isotopic anomalies, high ²⁶Al/²⁷Al ratios (∼ 0.1), and Ca and Ti isotopic anomalies, including the initial presence of short-lived ⁴¹Ca and ⁴⁴Ti. These isotopic features are qualitatively explained by nucleosynthesis in core collapse supernovae. We estimate that 76%, 50%, 7% and 1% of the KE3, KFA1, KFB1 and KFC1 grains, respectively, are supernova grains. We performed 3- and 4-zone supernova mixing calculations to reproduce the C, O (¹⁸O/¹⁶O) and Al isotopic ratios of the KE3 grains, using 15M_⊙ model calculations by Rauscher et al. (2002). Isotopic ratios of grains with high ¹²C/¹³C ratios (> 200) can be reproduced, whereas those of grains with ratios ⩽ 200 are hard to explain if we assume that graphite grains form in C-rich conditions.
We compared the distributions of the ¹²C/¹³C ratios of KFB1 and KFC1 grains and their s-process ⁸⁶Kr/⁸²Kr ratios inferred from bulk noble gas analysis to model calculations of asymptotic giant branch (AGB) stars with a range of mass and metallicity. We conclude that KFB1 grains with ¹²C/¹³C > 100 formed in the outflow of low-mass (1.5, 2 and 3M_⊙) low-metallicity (Z = 3 × 10^–3 for 1.5, 2 and 3M_⊙, Z = 6 × 10^–3 for 3M_⊙ only) AGB stars and that KFC1 grains with ¹²C/¹³C > 60 formed in those stars as well as in 5M_⊙ stars of solar and/or half-solar metallicities. Grains with ¹²C/¹³C < 20 in all the fractions seem to have multiple origins. Some of them formed in the ejecta of core-collapse supernovae. J stars and born-again AGB stars are also possible stellar sources.
We calculated the abundances of graphite grains from supernovae and AGB stars in the Murchison meteorite to be 0.24 ppm and 0.44 ppm, respectively, whereas those of SiC grains from supernovae and AGB stars are 0.065 ppm and 5.7 ppm, respectively. In contrast to graphite, AGB stars are a dominant source of SiC grains.
Since different mineral types have different residence times in the interstellar medium, their abundances in meteorites may not reflect original yields in stellar sources. Silicon carbide is mechanically more resistant than graphite and we assume that residence times of SiC are longer than those of graphite. Silicon carbide grains from AGB stars are much more abundant than graphite grains from AGB stars (5.7 ppm vs. 0.44 ppm). We speculate that one of the reasons that SiC grains from AGB stars are much more abundant than graphite grains from AGB stars is that major sources for graphite grains are 3 M_⊙ stars whereas for SiC lower-mass (1.5 – 2M_⊙) stars; lower-mass stars are more abundant. The abundances of supernova graphite grains and supernova SiC grains (0.24 ppm vs. 0.065 ppm) reflect grain formation and destruction in expanding supernova ejecta.

Reference
Amari S, Zinner E and Gallino R (in press) Isotopic study of presolar graphite from the murchison meteorite. Geochimica et Cosmochimica Acta
[doi:10.1016/j.gca.2014.01.006]
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Ertel S et al.¹ (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

¹UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, 38041 Grenoble, France

Context. The dust observed in debris disks is produced through collisions of larger bodies left over from the planet/planetesimal formation process. Spatially resolving these disks permits to constrain their architecture and thus that of the underlying planetary/planetesimal system.
Aims. Our Herschel open time key program DUNES aims at detecting and characterizing debris disks around nearby, sun-like stars. In addition to the statistical analysis of the data, the detailed study of single objects through spatially resolving the disk and detailed modeling of the data is a main goal of the project.
Methods. We obtained the first observations spatially resolving the debris disk around the sun-like star HIP 17439 (HD 23484) using the instruments PACS and SPIRE on board the Herschel Space Observatory. Simultaneous multi-wavelength modeling of these data together with ancillary data from the literature is presented.
Results. A standard single component disk model fails to reproduce the major axis radial profiles at 70  μm, 100  μm, and 160  μm simultaneously. Moreover, the best-fit parameters derived from such a model suggest a very broad disk extending from few au up to few hundreds of au from the star with a nearly constant surface density which seems physically unlikely. However, the constraints from both the data and our limited theoretical investigation are not strong enough to completely rule out this model. An alternative, more plausible, and better fitting model of the system consists of two rings of dust at approx. 30 au and 90 au, respectively, while the constraints on the parameters of this model are weak due to its complexity and intrinsic degeneracies.
Conclusions. The disk is probably composed of at least two components with different spatial locations (but not necessarily detached), while a single, broad disk is possible, but less likely. The two spatially well-separated rings of dust in our best-fit model suggest the presence of at least one high mass planet or several low-mass planets clearing the region between the two rings from planetesimals and dust.

Reference
Ertel S et al. (in press) Potential multi-component structure of the debris disk around HIP 17439 revealed by Herschel/DUNES. Astronomy & Astrophysics 561:A114.
[doi:10.1051/0004-6361/201219945]
Reproduced with permission © ESO

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