Evidence for pervasive mud volcanism in Acidalia Planitia, Mars

We have mapped 18,000+ circular mounds in a portion of southern Acidalia Planitia using their sizes, shapes, and responses in Nighttime IR. We estimate that 40,000+ of these features could occur in the area, with a distribution generally corresponding to the southern half of the proposed Acidalia impact basin. The mounds have average diameters of about 1 km and relief up to 180 m and most overlie units mapped as Early Amazonian.High resolution images of mound surfaces show relatively smooth veneers, apron-like extensions onto the plains, moats, and concentric circular crestal structures. Some images show lobate and flow-like features associated with the mounds. Albedo of the mounds is generally higher than that of the surrounding plains. Visible and near-infrared spectra suggest that the mounds and plains have subtle mineralogical differences, with the mounds having enhanced coatings or possibly greater quantities of crystalline ferric oxides.Multiple analogs for these structures were assessed in light of new orbital data and regional mapping. Mud volcanism is the closest terrestrial analogy, though the process in Acidalia would have had distinctly martian attributes. This interpretation is supported by the geologic setting of the Acidalia which sits at the distal end of the Chryse-Acidalia embayment into which large quantities of sediments were deposited through the Hesperian outflow channels. In its distal position, Acidalia would have been a depocenter for accumulation of mud and fluids from outflow sedimentation.Thus, the profusion of mounds in Acidalia is likely to be a consequence of this basin’s unique geologic setting. Basinwide mud eruption may be attributable to overpressure (developed in response to rapid outflow deposition) perhaps aided by regional triggers for fluid expulsion related to events such as tectonic or hydrothermal pulses, destabilization of clathrates, or sublimation of a frozen body of water. Significant release of gas may have been involved, and the extensive mud volcanism could have created long-lived conduits for upwelling groundwaters, providing potential habitats for an in situ microbiota.Mud volcanism transports minimally-altered materials from depth to the surface, and mud volcanoes in Acidalia, therefore, could provide access to samples from deep zones that would otherwise be inaccessible. Since the distal setting of Acidalia also would favor concentration and preservation of potentially-present organic materials, samples brought to the surface by mud volcanism could include biosignatures of possible past or even present life. Accordingly, the mounds of Acidalia may offer a new class of exploration target.     

Relationship between microseisms,geomagnetic activity and ionospheric absorption of radio waves

Summary Relatively good correlation between such remote phenomena as microseisms, geomagnetic activity and ionospheric absorption of radio waves has been observed. These phenomena are probably connected by a considerably increased penetration of energetic particles into the atmosphere under conditions of geomagnetic activity.     

Linking Tarim Basin sea retreat (west China) and Asian aridification in the late Eocene

The Tarim Basin in western China formed the easternmost margin of a shallow epicontinental sea that extended across Eurasia and was well connected to the western Tethys during the Paleogene. Climate modelling studies suggest that the westward retreat of this sea from Central Asia may have been as important as the Tibetan Plateau uplift in forcing aridification and monsoon intensification in the Asian continental interior due to the redistribution of the land‐sea thermal contrast. However, testing of this hypothesis is hindered by poor constraints on the timing and precise palaeogeographic dynamics of the retreat. Here, we present an improved integrated bio‐ and magnetostratigraphic chronological framework of the previously studied marine to continental transition in the southwest Tarim Basin along the Pamir and West Kunlun Shan, allowing us to better constrain its timing, cause and palaeoenvironmental impact. The sea retreat is assigned a latest Lutetian–earliest Bartonian age (ca. 41 Ma; correlation of the last marine sediments to calcareous nannofossil Zone CP14 and correlation of the first continental red beds to the base of magnetochron C18r). Higher up in the continental deposits, a major hiatus includes the Eocene–Oligocene transition (ca. 34 Ma). This suggests the Tarim Basin was hydrologically connected to the Tethyan marine Realm until at least the earliest Oligocene and had not yet been closed by uplift of the Pamir–Kunlun orogenic system. The westward sea retreat at ca. 41 Ma and the disconformity at the Eocene–Oligocene transition are both time‐equivalent with reported Asian aridification steps, suggesting that, consistent with climate modelling results, the sea acted as an important moisture source for the Asian continental interior.     

Application of a square wave potentiometry technique for electroreductive sulfur removal from a thiophenic model fuel

Thiophene-containing solutions were electroreductively desulfurized by a dynamic method. Initially, cyclic voltammetry was utilized to study thiophene electroadsorption from aqueous solution onto a platinum electrode surface and also to investigate the thiophene electroreductive behavior. Then, the solution was desulfurized via a square wave potentiometry method. The objective of this study was to find the optimal conditions. In this regard, the best adsorption potential, electroreduction potential, and square wave frequency were found to be ?0.54 V, ?0.95 V, and 1 Hz, respectively. Finally, a model fuel (containing 294 part per millions thiophene) was desulfurized by the square wave potentiometry method. Gas chromatography and Fourier transform infrared spectroscopy were used to examine the feed and product solutions. Gas chromatographic measurements revealed that sulfur content decreased to 55 part per millions. Based on the acquired results, electroreductive desulfurization could be designated as an efficient superseded for the commercial hydrodesulfurization process. However, more studies must perform to overcome technical limitations of electroreductive desulfurization technique and to guarantee its reliability.     

Spatial distribution of solar flares in 23rd solar cycle

H-alpha flares accompanied by the X-radiation f ?? 10^?6 wm^?2 in power are examined; 2331 flares were registered during the first half of the 23rd solar cycle (1997?C2000). The specific power of the X-radiation of the flares monotonically doubles from the minimum to the maximum of the sunspot. An increase in the number of flares in each solar rotation is nonmonotonic and disproportional to the relative number of sunspots. Several longitudinal intervals with increased flare activity can be distinguished in the entire time interval of five to ten rotations. The longitudinal distributions of flares and boundaries of the sector structures of a large-scale magnetic field differ considerably. This confirms the existence of two types of zero lines; the first type is determined by active regions, and the second one is determined by large-scale structures with weak magnetic fields. The flares concentrate near Hale??s zero lines of the first type.     

Investigation on strength and stability of jointed rock mass using three‐dimensional numerical manifold method

This paper proposes a numerical model for jointed rock masses within the 3‐D numerical manifold method (NMM) framework equipped with a customized contact algorithm. The strength of rock sample containing a few sets of discontinuities is first investigated. The results of models with simple geometries are compared with the available analytical solutions to verify the developed computer code, whereas models with complex geometries are simulated to better understand the fundamental behavior and failure mechanism of jointed rock mass. Furthermore, the stability of jointed rock mass in an underground excavation is studied, where rock failure process is determined by the 3‐D NMM simulation. The simulation results provide valuable guidance on excavation process design and stabilization design in rock engineering practice. Copyright © 2012 John Wiley & Sons, Ltd.     

Tectonic setting of the Azores Plateau deduced from a OBS survey

The studies of Azores seismicity generally show shocks with either normal faulting or right-lateral strike-slip along the ESE direction, compatible with a eastward relative motion of the Eurasian (EU) relative to the African (AF) plate. However, the 1 January 1980 earthquake was interpreted as a clear left-lateral strike-slip shock along the N150E direction. This pattern is difficult to explain in terms of the relative motion between the EU, AF and North American (NA) plates: all available models for the present day movement of this triple junction fail to explain the regional variability in the stress conditions of the area. Here we present data from a 34-day long Ocean Bottom Seismograph array deployment. We show that the seismicity is distributed along a band aligned with the island chain itself, and is concentrated along several faults with an approximate N150E strike, cutting the Azores plateau in all the area covered by the OBS network. The combination of these new results with other geophysical data permits us to conclude that the tectonic setting of the Azores plateau is characterised by the existence of two sets of faults, in the N120E and N150E directions, defining several crustal blocks, whose relative motion accommodates the interaction of the three megaplates. The deformation of these tectonic blocks is probably driven by the shear between the EU and AF plates. This model explains well the spatial variability of the stress conditions in the Azores domain, the combination of dextral and sinistral strike slip mechanisms and the observed seismotectonics of the Azores islands.