A hydrothermal system associated with the Siljan impact structure, Sweden--implications for the search for fossil life on Mars

The Siljan ring structure (368 +/- 1.1 Ma) is the largest known impact structure in Europe. It isa 65-km-wide, eroded, complex impact structure, displaying several structural units, including a central uplifted region surrounded by a ring-shaped depression. Associated with the impact crater are traces of a post-impact hydrothermal system indicated by precipitated and altered hydrothermal mineral assemblages. Precipitated hydrothermal minerals include quartz veins and breccia fillings associated with granitic rocks at the outer margin of the central uplift, and calcite, fluorite, galena, and sphalerite veins associated with Paleozoic carbonate rocks located outside the central uplift. Two-phase water/gas and oil/gas inclusions in calcite and fluorite display homogenization temperatures between 75 degrees C and 137 degrees C. With an estimated erosional unloading of approximately 1 km, the formation temperatures were probably not more than 10-15 degrees C higher. Fluid inclusion ice-melting temperatures indicate a very low salt content, reducing the probability that the mineralization was precipitated during the Caledonian Orogeny. Our findings suggest that large impacts induce low-temperature hydrothermal systems that may be habitats for thermophilic organisms. Large impact structures on Mars may therefore be suitable targets in the search for fossil thermophilic organisms.     

The Next Big Things for Top-market BizAv OEMs

<正>AS OEM's display their flagship ultra-longrange, purpose-built business jetsspecifically Bombardier's Global 7500,Gulfstream's G650ER, and Dassault's Falcon 8X-this week at EBACE 2019, speculation stoked by the manufacturers themselves abounds on what comes next.When Gulfstream's flagship G650 entered service in December 2012, the Savannah airframer decisively seized the mantle of largest dedicated business jet. That was reinforced when the 7,500-nm-range G650ER variant joined its line     

Putative fossilized fungi from the lithified volcaniclastic apron of Gran Canaria, Spain

We report the discovery of fossilized filamentous structures in samples of the lithified, volcaniclastic apron of Gran Canaria, which were obtained during Leg 157 of the Ocean Drilling Program (ODP). These filamentous structures are 2-15 μm in diameter and several hundred micrometers in length and are composed of Si, Al, Fe, Ca, Mg, Na, Ti, and C. Chitin was detected in the filamentous structures by staining with wheat germ agglutinin dye conjugated with fluorescein isothiocyanate (WGA-FITC), which suggests that they are fossilized fungal hyphae. The further elucidation of typical filamentous fungal morphological features, such as septa, hyphal bridges, and anastomosis and their respective sizes, support this interpretation. Characteristic structures that we interpreted as fossilized spores were also observed in association with the putative hyphae. The fungal hyphae were found in pyroxene phenocrysts and in siderite pseudomorphs of a basalt breccia. The fungal colonization of the basalt clasts occurred after the brecciation but prior to the final emplacement and lithification of the sediment at ～16-14 Ma. The siderite appears to have been partially dissolved by the presence of fungal hyphae, and the fungi preferentially colonized Fe-rich carbonates over Fe-poor carbonates (aragonite). Our findings indicate that fungi may be an important geobiological agent in subseafloor environments and an important component of the deep subseafloor biosphere, and that hydrothermal environments associated with volcanism can support a diverse ecosystem, including eukaryotes.     

Micromission spacecraft: a low-cost, high-capability platform for space science missions

The Ball Micromission Spacecraft (MSC) is a multi-purpose platform capable of supporting science missions at distances from the Sun ranging from 0.7 to 1.7 AU. In the baseline scenario, MSC is launched as a secondary payload on an Ariane 5 rocket from Kourou, French Guiana, to GTO using the Ariane 5 structure for auxiliary payloads (ASAP5). The maximum launch wet mass is 242 Kg and can include up to 45 Kg of payload depending on AV needs. The on-board propulsion system is used for maneuvering in the Earth-Moon system and injecting the spacecraft into its final orbit or trajectory. For Mars missions, MSC enables orbiting Mars for science payloads and/or communications and navigation assets, or for precision Mars fly-bys to drop up to six probes. The micromissions spacecraft bus can be used for science targets other than Mars, including the Moon, Earth, Venus, Earth-Sun Lagrange points, or other small bodies. This paper summarizes the current spacecraft concept and describes the multimission spacecraft bus implementation in more detail.     

Gravitational-collapse supernovae

The gravitational collapse of the core of a massive star releases ample energy for a supernova explosion. The mechanisms by which this energy can be imparted to the outer parts of the stars to actually yield an explosion is outlined, and some of the related physical processes are examined. In particular the generation of entropy and the loss of neutrinos during the collapse of the core and the generation of lepton-driven buoyancy instabilities are discussed in some detail.     

A solar extreme ultraviolet telescope and spectrograph for Shuttle/Spacelab

An instrument for advanced studies of the solar corona is described. Its optical system provides nearly stigmatic imaging of selected portions of the Sun over the spectral range from 22.5 to 44.0 nm. Both spectroheliograms and emission line profiles of coronal features will be obtained over a wide range of coronal temperatures.Proceedings of the Conference Solar Physics from Space, held at the Swiss Federal Institute of Technology Zurich (ETHZ), 11–14 November 1980.This paper was presented at the conference by U. Feldman.     

双膜热流计的研究及其应用

 本文对用于测量涡轮叶片和涡轮外环换热的高频双膜热流计进行了理论分析,并给出了对双膜热流计的校验方法,阐明了双膜热流计的设计及其应用。