Combining shock barometry with numerical modeling: insights into complex crater formation – The example of the Siljan impact structure (Sweden)

Siljan, central Sweden, is the largest known impact structure in Europe. It was formed at about 380 Ma, in the late Devonian period. The structure has been heavily eroded to a level originally located underneath the crater floor, and to date, important questions about the original size and morphology of Siljan remain unanswered. Here we present the results of a shock barometry study of quartz-bearing surface and drill core samples combined with numerical modeling using iSALE. The investigated 13 bedrock granitoid samples show that the recorded shock pressure decreases with increasing depth from 15 to 20 GPa near the (present) surface, to 10–15 GPa at 600 m depth. A best-fit model that is consistent with observational constraints relating to the present size of the structure, the location of the downfaulted sediments, and the observed surface and vertical shock barometry profiles is presented. The best-fit model results in a final crater (rim-to-rim) diameter of ~65 km. According to our simulations, the original Siljan impact structure would have been a peak-ring crater. Siljan was formed in a mixed target of Paleozoic sedimentary rocks overlaying crystalline basement. Our modeling suggests that, at the time of impact, the sedimentary sequence was approximately 3 km thick. Since then, there has been around 4 km of erosion of the structure

Combined neutron and x-ray tomography—a versatile and non-destructive tool in planetary geosciences

With several upcoming sample return missions, such as the Mars Sample Return Campaign, non-destructive methods will be key to maximizing their scientific output. In this study, we demonstrate that the combination of neutron and X-ray tomography provides an important tool for the characterization of such valuable samples. These methods allow quantitative analyses of internal sample features and also provide a guide for further destructive analyses with little to no sample treatment, which maintains sample integrity, including minimizing the risk of potential contamination. Here, we present and review the results from four case studies of terrestrial impactites and meteorites along with their analytical setup. Using combined X-ray and neutron tomography, a Ni-Fe silicide spherule, that is, projectile material, was located within a Libyan Desert Glass sample and the distribution of hydrous phases was pinpointed in selected impactite samples from the Chicxulub IODP-ICDP Expedition 364 drill core and the Luizi impact structure, as well as in the Miller Range 03346 Martian meteorite

Rochechouart 2017-Drilling Campaign: First Results

No abstract available

Massive variceal bleeding secondary to splenic vein thrombosis successfully treated with splenic artery embolization: a case report

<p>Abstract</p> <p>Introduction</p> <p>Splenic vein thrombosis results in localized portal hypertension called sinistral portal hypertension, which may also lead to massive upper gastrointestinal bleeding. Symptomatic sinistral portal hypertension is usually best treated by splenectomy, but interventional radiological techniques are safe and effective alternatives in the management of a massive hemorrhage, particularly in cases that have a high surgical risk.</p> <p>Case presentation</p> <p>We describe a 23-year-old Greek man with acute massive gastric variceal bleeding caused by splenic vein thrombosis due to a missing von Leiden factor, which was successfully managed with splenic arterial embolization.</p> <p>Conclusions</p> <p>Interventional radiological techniques are attractive alternatives for patients with a high surgical risk or in cases when the immediate surgical excision of the spleen is technically difficult. Additionally, surgery is not always successful because of the presence of numerous portal collaterals and adhesion. Splenic artery embolization is now emerging as a safe and effective alternative to surgery in the management of massive hemorrhage from gastric varices due to splenic vein thrombosis, which often occurs in patients with hypercoagulability.</p

CIRIR programs: drilling and research opportunities at the Rochechouart Impact Structure

International audienc

Serum Proteins in Liver Cirrhosis: Effects of Shunt Surgery

Peer Reviewe

A Consortium status report: the characterisation of the asteroid Itokawa regolith - a correlated study by X-ray tomography, micro-raman spectroscopy, and high-sensitivity noble gas analysis

Precious samples from S-type as-teroid 25143 Itokawa have been sampled by the JAXA (Japanese Space Agency) Hayabusa mission in 2005 and returned to Earth in 2010. Itokawa is, succeeding the Moon and comet Wild 2, the third planetary body successfully probed by a sample return mission. The initial studies revealed that Itokawa consists mostly of type LL5-6 material. It experienced severe surface alteration due to space weathering, as docu-mented by surficial, nanosize S-and Fe-bearing phases in some grains. Noble gas studies indicate that Itokawa experiences a surprisingly intense surface loss at a rate of tens of cm/Ma, implying that Itokawa (largest dimension ~540 m) will be destroyed quickly. We received material through JAXA in Sept. 2012 and aim to analyze noble gases in Itokawa samples with high sensitivity, including Kr and Xe, which could not be studied previously, because of the low concentrations. We will combine the noble gas studies with scanning microRaman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and synchro-tron radiation X-ray tomographic microscopy (SRXTM). These provide non-destructive characteri-zations of grain density, mineralogy, structure, and potential space weathering, which are essential to as-sess gas concentrations of potentially present cosmogenic, solar, trapped and radiogenic compo-nents. Here, we summarize the work of our consortium performed so far. Further studies will be presented at the meeting

The mass, morphology, and internal structures of three particles from the HAYABUSA sample return mission, analyzed with Synchrotron radiation X-ray tomographic microscopy.

The Hayabusa sample return mission, launched in 2003 by the Japan Aerospace Exploration Agency (JAXA), was the first ever space mission to sample material from an asteroid: the S-type, near-Earth asteroid (25143) Itokawa. More than 1500 particles, varying in size from <1 μm to 180 μm, were recovered from the uppermost regolith layer of the asteroid. The main aim of this study is to determine a precise mass for three of these particles. The mass will then be used in a forthcoming study where the concentration of solar wind derived, trapped, and cosmogenic noble gases of the individual particles will be measured. Due to the small particle size (75-145 μm), a normal weighing procedure on a micro- balance would result in large errors (up to 100%) in the mass and thus also in the noble gas concentrations, as well as the cosmic-ray-exposure (CRE) ages derived from cosmogenic noble gases. A precise mass, combined with the detection limit of the noble gas spectrometer used, allows the determination of the minimum cosmic-ray-exposure age that could still be resolved. The mass is measured by determining the volume of the constituent mineral phases (with known densities), using synchrotron radiation X-ray tomographic microscopy (SRXTM). This also allows non-destructive studies of the morphology and internal structure of the particles. While Hayabusa particles have been studied with SRXTM before, none of the particles from this study have so far been analyzed

A 3-D study of mineral inclusions in chromite from ordinary chondrites using synchrotron radiation X-ray tomographic microscopy-Method and applications

Abstract– A method is described for imaging in 3-D the interiors of meteoritic chromite grains and their inclusions using synchrotron radiation X-ray tomographic microscopy. In ordinary chondrites, chromite is the only common mineral that survives long-term weathering on Earth. Information about the silicate matrix of the original meteorite, however, can be derived from mineral inclusions preserved in the protecting chromite. The inclusions are crucial in the classification of fossil meteorites as well as sediment-dispersed chromite grains from decomposed meteorites and larger impacts, as these are used for characterizing the past influx of material to Earth, but have previously been difficult to locate. The method is non-destructive and time efficient for locating inclusions. The method allowed quantitative and morphological studies of both host chromite grains and inclusions in three dimensions. The study of 385 chromite grains from eight chondrites (H4–6, L4–6, LL4, LL6) reveals that inclusions are abundant and equally common in all samples. Almost two-thirds of all chromite grains contain inclusions, regardless of group and type. The study also shows that the size of the inclusions and the host chromite grains, as well as the number of inclusions, within the host chromite grains vary with petrographic type. Thus, the petrographic type of the host of a suite of chromite grains can be determined based solely on inclusion content. The study also revealed that the amount of fractures in the host chromite can be correlated to previously assigned shock stages for the various chondrites. The study has thus shown that the features and inclusions of fossil chromite grains can give similar information about a former host meteorite as do studies of an unweathered whole meteorite, meaning that this technique is essential in the studies of ancient meteorite flux to Earth