New active galactic nuclei science cases with interferometry

Infrared (IR) interferometry has made widely recognised contributions to the way we look at the dusty environment of supermassive black holes on parsec scales. It finally provided direct evidence for orientation-dependent unification of active galaxies, however it also showed that the classical “torus” picture is oversimplified. New scientific opportunities for AGN have been suggested, and will soon be carried out, focusing on the dynamical aspects of spectrally and spatially resolved interferometry, as well as the potential to employ interferometry for cosmology. This will open interferometry to new scientific communities.     

Production key figures for planning the mining of manganese nodules

Under the impression of decreasing ore grades and increasing production costs in conventional mining, seafloor minerals came into focus. Having gained a basic understanding of geological settings, there is still a lack of tools to assess and plan future mining projects in the deep-sea. This paper contributes to a mining concept which is inspired by the high-tech farming industry: strip mining. Potential mining fields are identified using image filters in conjunction with hydroacoustic backscatter data and slope angles and are portioned into long, narrow strips. In the framework of the EU-funded Blue Mining project, these methods were applied to a part of the eastern German exploration area, located in the manganese nodule belt of the Clarion Clipperton Zone, Pacific Ocean. Both, the mapping technique and the mining concept presented in this paper can be used in early-stage feasibility studies to derive estimates on production key figures for seafloor manganese nodule mining.     

The reaction of carbonates in contact with laser-generated,superheated silicate melts: Constraining impact metamorphism of carbonate-bearing target rocks

We simulated entrainment of carbonates (calcite, dolomite) in silicate impact melts by 1-bar laser melting of silicate–carbonate composite targets, using sandstone, basalt, calcite marble, limestone, dolomite marble, and iron meteorite as starting materials. We demonstrate that carbonate assimilation by silicate melts of variable composition is extremely fast (seconds to minutes), resulting in contamination of silicate melts with carbonate-derived CaO and MgO and release of CO₂ at the silicate melt–carbonate interface. We identify several processes, i.e., (1) decomposition of carbonates releases CO₂ and produces residual oxides (CaO, MgO); (2) incorporation of residual oxides from proximally dissociating carbonates into silicate melts; (3) rapid back-reactions between residual CaO and CO₂ produce idiomorphic calcite crystallites and porous carbonate quench products; (4) high-temperature reactions between Ca-contaminated silicate melts and carbonates yield typical skarn minerals and residual oxide melts; (5) mixing and mingling between Ca- or Ca,Mg-contaminated and Ca- or Ca,Mg-normal silicate melts; (6) precipitation of Ca- or Ca,Mg-rich silicates from contaminated silicate melts upon quenching. Our experiments reproduce many textural and compositional features of typical impact melts originating from silicate–carbonate targets. They reinforce hypotheses that thermal decomposition of carbonates, rapid back-reactions between decomposition products, and incorporation of residual oxides into silicate impact melts are prevailing processes during impact melting of mixed silicate–carbonate targets. However, by comparing our results with previous studies and thermodynamic considerations on the phase diagrams of calcite and quartz, we envisage that carbonate impact melts are readily produced during adiabatic decompression from high shock pressure, but subsequently decompose due to heat influx from coexisting silicate impact melts or hot breccia components. Under certain circumstances, postshock conditions may favor production and conservation of carbonate impact melts. We conclude that the response of mixed carbonate–silicate targets to impact might involve melting and decomposition of carbonates, the dominant response being governed by a complex variety of factors.     

Scanning sky monitor (SSM) onboard AstroSat

Scanning Sky Monitor (SSM) onboard AstroSat is an Xray sky monitor in the soft X-ray band designed with a large field of view to detect and locate transient X-ray sources and alert the astronomical community about interesting phenomena in the X-ray sky. SSM comprises position sensitive proportional counters with 1D coded mask for imaging. There are three detector units mounted on a platform capable of rotation which helps covering about 50% of the sky in one full rotation. This paper discusses the elaborate details of the instrument and few immediate results from the instrument after launch.     

Seismicity in the block mountains between Halle and Leipzig,Central Germany: centroid moment tensors,ground motion simulation,and felt intensities of two <Emphasis Type="Italic">M</Emphasis> ≈ 3 earthquakes in 2015 and 2017

On April 29, 2017 at 0:56 UTC (2:56 local time), an M_W =?2.8 earthquake struck the metropolitan area between Leipzig and Halle, Germany, near the small town of Markranstädt. The earthquake was felt within 50 km from the epicenter and reached a local intensity of I₀ = IV. Already in 2015 and only 15 km northwest of the epicenter, a M_W =?3.2 earthquake struck the area with a similar large felt radius and I₀ = IV. More than 1.1 million people live in the region, and the unusual occurrence of the two earthquakes led to public attention, because the tectonic activity is unclear and induced earthquakes have occurred in neighboring regions. Historical earthquakes south of Leipzig had estimated magnitudes up to M_W ≈?5 and coincide with NW-SE striking crustal basement faults. We use different seismological methods to analyze the two recent earthquakes and discuss them in the context of the known tectonic structures and historical seismicity. Novel stochastic full waveform simulation and inversion approaches are adapted for the application to weak, local earthquakes, to analyze mechanisms and ground motions and their relation to observed intensities. We find NW-SE striking normal faulting mechanisms for both earthquakes and centroid depths of 26 and 29 km. The earthquakes are located where faults with large vertical offsets of several hundred meters and Hercynian strike have developed since the Mesozoic. We use a stochastic full waveform simulation to explain the local peak ground velocities and calibrate the method to simulate intensities. Since the area is densely populated and has sensitive infrastructure, we simulate scenarios assuming that a 12-km long fault segment between the two recent earthquakes is ruptured and study the impact of rupture parameters on ground motions and expected damage.     

The development of radio astronomy

Following the detection of extraterrestrial radio waves in 1932 by Karl Jansky, radio astronomy developed quickly after World War II. It established itself soon as a new branch of astronomy with today's outstanding record in the detection of new phenomena in space. These have been honoured by a number of Nobel prizes. Radio astronomy largely depends on technical developments in receiver technology, antenna systems, electronics and computing power. Ever shorter wavelengths down to the submm‐wavelength range became accessible, resulting in new exciting discoveries. However, now and in future care must be taken, in particular for the lower frequency range, of harmful man‐made interferences, which might mask the weak signals from space. New international facilities with orders‐of‐magnitude higher sensitivity like ALMA and SKA are planned or under construction. Space‐borne observatories like PLANCK will detect weak fluctuations of the cosmic microwave background, which will constrain cosmological models with an unprecedented accuracy.     

Statistical analysis of the 2012–2013 Torreperogil–Sabiote seismic series,Spain

The study of earthquake swarms and their characteristics can improve our understanding of the transient processes that provoke seismic crises. The spatio-temporal process of the energy release is often linked with changes of statistical properties, and thus, seismicity parameters can help to reveal the underlying mechanism in time and space domains. Here, we study the Torreperogil–Sabiote 2012–2013 seismic series (southern Spain), which was relatively long lasting, and it was composed by more than 2000 events. The largest event was a magnitude 3.9 event which occurred on February 5, 2013. It caused slight damages, but it cannot explain the occurrence of the whole seismic crises which was not a typical mainshock–aftershock sequence. To shed some light on this swarm occurrence, we analyze the change of statistical properties during the evolution of the sequence, in particular, related to the magnitude and interevent time distributions. Furthermore, we fit a modified version of the epidemic type aftershock sequence (ETAS) model in order to investigate changes of the background rates and the trigger potential. Our results indicate that the sequence was driven by an aseismic transient stressing rate and that the system passes after the swarm occurrence to a new forcing regime with more typical tectonic characteristics.     

An evaluation and implementation of the regional coupled ice-ocean model of the Baltic Sea

Ocean Dynamics - A three-dimensional, regional coupled ice-ocean model based on the open-source Community Earth System Model has been developed and implemented for the Baltic Sea. The model...     

Architecture of tunnel valleys in the southeastern North Sea: new insights from high-resolution seismic imaging

Tunnel valleys are assumed to form near the margin of ice sheets. Hence, they can be used to reconstruct the dynamics of former ice margins. The detailed formation and infill of tunnel valleys, however, are still not well understood. Here, we present a dense grid of high-resolution 2D multi-channel reflection seismic data from the German sector of the southeastern North Sea imaging tunnel valleys in very great detail. Three tunnel valley systems were traced over distances ranging between 11 and 21 km. All tunnel valleys are completely filled and buried. They differ in incision depth, incision width and number of incisions. The tunnel valleys cut 130–380 m deep into Neogene, Palaeogene and Cretaceous sediments; they show a lower V-shaped and an upper U-shaped morphology. For individual tunnel valleys, the overall incision direction ranges from east–west to northeast–southwest. Two tunnel valleys intersect at an oblique angle without reuse of the thalweg. These valleys incise into a pre-existing glaciotectonic complex consisting of thrust sheets in the northwest of the study area. The analysis of the glaciotectonic complex and the tunnel valleys leads us to assume that we identified several marginal positions of (pre-)Elsterian ice lobes in the southeastern North Sea.     

New records of Ediacaran Acraman ejecta in drillholes from the Stuart Shelf and Officer Basin,South Australia

Abstract— New occurrences of the Acraman impact ejecta layer were recently discovered in two South Australian drillholes, SCYW‐79 1a (Stuart Shelf) and Munta 1 (Officer Basin) using lithostratigraphy, acritarch biostratigraphy, carbon isotope stratigraphy, and biomarker anomalies to predict the stratigraphic position. The ejecta layer is conspicuous because it consists of pink, sandsized, angular fragments of volcanic rock distributed along the bedding plane surface of green marine siltstone. In SCYW‐79 1a it forms a layer 5 mm thick; in Munta 1 the ejecta layer is thin and discontinuous because of its distance (?550 km) from the impact structure. Palynological, biomarker, and carbon isotope anomalies can now be shown to coincide with the ejecta layer in SCYW‐79 1a and Munta 1 suggesting the Acraman impact event may have had far reaching influences on the rapidly evolving Ediacaran biological and geochemical cycles.