78 research outputs found
Late metal-silicate separation on the IAB parent asteroid: Constraints from combined W and Pt isotopes and thermal modelling
The short-lived Hf-W decay system is a powerful chronometer
for constraining the timing of metal-silicate separation and core formation in
planetesimals and planets. Neutron capture effects on W isotopes, however,
significantly hamper the application of this tool. In order to correct for
neutron capture effects, Pt isotopes have emerged as a reliable in-situ neutron
dosimeter. This study applies this method to IAB iron meteorites, in order to
constrain the timing of metal segregation on the IAB parent body. The
W values obtained for the IAB iron meteorites range from -3.61
0.10 to -2.73 0.09. Correlating Pt with
W data yields a pre-neutron capture W of -2.90 0.06. This
corresponds to a metal-silicate separation age of 6.0 0.8 Ma after CAI
for the IAB parent body, and is interpreted to represent a body-wide melting
event. Later, between 10 and 14 Ma after CAI, an impact led to a catastrophic
break-up and subsequent reassembly of the parent body. Thermal models of the
interior evolution that are consistent with these estimates suggest that the
IAB parent body underwent metal-silicate separation as a result of internal
heating by short-lived radionuclides and accreted at around 1.4 0.1 Ma
after CAIs with a radius of greater than 60 km.Comment: 11 pages, 8 figures, 2 tables; open access article under the CC
BY-NC-ND license (see http://creativecommons.org/licenses/by-nc-nd/4.0/
Fatal spirorchiidosis in European pond turtles (Emys orbicularis) in Switzerland
Infections with intravascular digenean trematodes of the Spirorchiidae family (spirorchiidoses) are of great conservation concern both in marine and freshwater turtles due to their pathogenic potential. Between 2014 and 2021, Spirorchis sp. infections associated with granulomatous inflammation and sudden death were detected in European pond turtles (Emys orbicularis) from three conservation breeding facilities in Switzerland. Blood fluke eggs associated with lesions were found in the intestine, spleen, testis, skeletal musculature, heart, kidneys, stomach, pancreas, liver, lung, and meninges from nine pond turtles submitted for necropsy and in the intestinal content from five of these animals. Two novel polymerase chain reactions (PCRs) targeting the 28S ribosomal RNA gene and the ITS2 region and subsequent sequencing revealed 100% nucleotide identity with a Spirorchis sp. previously isolated from an Escambia map turtle (Graptemys ernsti) in the USA. Our findings suggest a spill-over event secondary to direct or indirect contact with invasive North American turtle species in Switzerland. We describe the clinical, haematological, ultrasonographical, endoscopical, parasitological, pathological, and molecular findings associated with spirorchiid blood fluke infections of the Spirorchis genus in E. orbicularis, as well as the biosecurity measures that were developed to prevent the spread of this parasite among breeding and highly endangered free-ranging E. orbicularis populations in Switzerland
Nucleosynthetic osmium isotope anomalies in acid leachates of the Murchison meteorite
We present osmium isotopic results obtained by sequential leaching of the
Murchison meteorite, which reveal the existence of very large internal
anomalies of nucleosynthetic origin. The Os isotopic anomalies are correlated,
and can be explained by the variable contributions of components derived from
the s, r and p-processes of nucleosynthesis. Much of the s-process rich osmium
is released by relatively mild leaching, suggesting the existence of an easily
leachable s-process rich presolar phase, or alternatively, of a chemically
resistant r-process rich phase. The s-process composition of Os released by
mild leaching diverges slightly from that released by aggressive digestion
techniques, perhaps suggesting that the presolar phases attacked by these
differing procedures condensed in different stellar environments. The
correlation between 190Os and 188Os can be used to constrain the s-process
190Os/188Os ratio to be 1.275 pm 0.043. Such a ratio can be reproduced in a
nuclear reaction network for a MACS value for 190Os of ~200 pm 22 mbarn at 30
keV. We also present evidence for extensive internal variation of 184Os
abundances in the Murchison meteorite. This suggests that p process rich
presolar grains (e.g., supernova condensates) may be present in meteorites in
sufficient quantities to influence the Os isotopic compositions of the
leachates.Comment: 40 pages, 9 figures, 2 tables. Accepted for publication in Earth and
Planetary Science Letter
Radiogenic p-isotopes from type Ia supernova, nuclear physics uncertainties, and galactic chemical evolution compared with values in primitive meteorites
The nucleosynthesis of proton-rich isotopes is calculated for multi-dimensional Chandrasekhar-mass models of Type Ia supernovae (SNe Ia) with different metallicities. The predicted abundances of the short-lived radioactive isotopes 92Nb, 97, 98Tc, and 146Sm are given in this framework. The abundance seeds are obtained by calculating s-process nucleosynthesis in the material accreted onto a carbon-oxygen white dwarf from a binary companion. A fine grid of s-seeds at different metallicities and 13C-pocket efficiencies is considered. A galactic chemical evolution model is used to predict the contribution of SN Ia to the solar system p-nuclei composition measured in meteorites. Nuclear physics uncertainties are critical to determine the role of SNe Ia in the production of 92Nb and 146Sm. We find that, if standard Chandrasekhar-mass SNe Ia are at least 50% of all SN Ia, they are strong candidates for reproducing the radiogenic p-process signature observed in meteorites.Peer reviewedFinal Accepted Versio
Abundances of the elements in the solar system
A review of the abundances and condensation temperatures of the elements and
their nuclides in the solar nebula and in chondritic meteorites. Abundances of
the elements in some neighboring stars are also discussed.Comment: 42 pages, 11 tables, 8 figures, chapter, In Landolt- B\"ornstein, New
Series, Vol. VI/4B, Chap. 4.4, J.E. Tr\"umper (ed.), Berlin, Heidelberg, New
York: Springer-Verlag, p. 560-63
High-efficiency p-i-n a-Si:H solar cells with low boron cross-contamination prepared in a large-area single-chamber PECVD reactor
Triple F - a comet nucleus sample return mission
The Triple F (Fresh From the Fridge) mission, a Comet Nucleus Sample Return, has been proposed to ESA's Cosmic Vision program. A sample return from a comet enables us to reach the ultimate goal of cometary research. Since comets are the least processed bodies in the solar system, the proposal goes far beyond cometary science topics (like the explanation of cometary activity) and delivers invaluable information about the formation of the solar system and the interstellar molecular cloud from which it formed. The proposed mission would extract three sample cores of the upper 50cm from three locations on a cometary nucleus and return them cooled to Earth for analysis in the laboratory. The simple mission concept with a touch-and-go sampling by a single spacecraft was proposed as an M-class mission in collaboration with the Russian space agency ROSCOSMOS. © The Author(s) 2008
The Stubenberg meteorite—An LL6 chondrite fragmental breccia recovered soon after precise prediction of the strewn field
On March 6, 2016 at 21:36:51 UT, extended areas of Upper Austria, Bavaria (Germany) and the southwestern part of the Czech Republic were illuminated by a very bright bolide. This bolide was recorded by instruments in the Czech part of the European Fireball Network and it enabled complex and precise description of this event including prediction of the impact area. So far six meteorites totaling 1473 g have been found in the predicted area. The first pieces were recovered on March 12, 2016 on a field close to the village of Stubenberg (Bavaria). Stubenberg is a weakly shocked (S3) fragmental breccia consisting of abundant highly recrystallized rock fragments embedded in a clastic matrix. The texture, the large grain size of plagioclase, and the homogeneous compositions of olivine (Fa31.4) and pyroxene (Fs25.4) clearly indicate that Stubenberg is an LL6 chondrite breccia. This is consistent with the data on O, Ti, and Cr isotopes. Stubenberg does not contain solar wind-implanted noble gases. Data on the bulk chemistry, IR spectroscopy, cosmogenic nuclides, and organic components also indicate similarities to other metamorphosed LL chondrites. Noble gas studies reveal that the meteorite has a cosmic ray exposure (CRE) age of 36 ± 3 Ma and that most of the cosmogenic gases were produced in a meteoroid with a radius of at least 35 cm. This is larger than the size of the meteoroid which entered the Earth's atmosphere, which is constrained to <20 cm from short-lived radionuclide data. In combination, this might suggest a complex exposure history for Stubenberg.PostprintPeer reviewe
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