Experimental evidence for the potential impact ejection of viable microorganisms from Mars and Mars-like planets

Bacterial spores (Bacillus subtilis), cyanobacteria (Chroococcidiopsis sp.), and lichen (Xanthoria elegans) embedded in martian analogue rock (gabbro) were exposed to shock pressures between 5 and 50 GPa which is the range of pressures observed in martian meteorites. The survival of Bacillus subtilis and Xanthoria elegans up to 45 GPa and of Chroococcidiopsis sp. up to 10 GPa supports the possibility of transfer of life inside meteoroids between Mars and Earth and it implies the potential for the transfer of life from any Mars-like planet to other habitable planets in the same stellar system.     

Paleomagnetic and rock magnetic study of the Yaxcopoil‐1 impact breccia sequence,Chicxulub impact crater (Mexico)

Abstract— Results of a detailed paleomagnetic and rock magnetic study of samples of the impact breccia sequence cored in the Yaxcopoil‐1 (Yax‐1) borehole between about 800 m and 896 m are presented. The Yax‐1 breccia sequence occurs from 794.63 m to 894.94 m and consists of redeposited melt‐rich, clast‐size sorted, fine‐grained suevites; melt‐rich, no clast‐size sorting, medium‐grained suevites; coarse suevitic melt agglomerates; coarse melt‐rich heterogeneous suevites; brecciated suevites; and coarse carbonate and silicate melt suevites. The low‐field susceptibility ranges from ?0.3 to 4018 times 10^?6 SI, and the NRM intensity ranges from 0.02 mA/m up to 37510 mA/m. In general, the NRM intensity and magnetic susceptibility present wide ranges and are positively correlated, pointing to varying magnetic mineral contents and textures of the melt‐rich breccia sequence. The vectorial composition and magnetic stability of NRM were investigated by both stepwise alternating field and thermal demagnetization. In most cases, characteristic single component magnetizations are observed. Both upward and downward inclinations are present through the sequence, and we interpret the reverse magnetization as the primary component in the breccias. Both the clasts and matrix forming the breccia appear to have been subjected to a wide range of temperature/pressure conditions and show distinct rock magnetic properties. An extended interval of remanence acquisition and secondary partial or total remagnetization may explain the paleomagnetic results.     

Laser argon‐40‐argon‐39 age studies of Dar al Gani 262 lunar meteorite

Abstract— The laser ⁴⁰Ar‐³⁹Ar dating technique has been applied to the Dar al Gani (DaG) 262 lunar meteorite, a polymict highland regolith breccia, to determine the crystallisation age and timing of shock events experienced by this meteorite. Laser stepped‐heating analyses of three dominantly feldspathic fragments (DaG‐1, DaG‐2, and DaG‐3) revealed the presence of trapped Ar, mostly released at intermediate and high temperatures, with an ⁴⁰Ar/³⁶Ar value of ～2.8. Trapped Ar is most likely released from melt glass present as small veins within the fragments. The ⁴⁰Ar‐³⁹Ar ages determined for the three fragments are ～3.0 Ga for DaG‐1 and DaG‐2 and 2.0 Ga for DaG‐3 and probably relate to major impact events. Laser spot analyses were performed on a feldspathic clast, an impact crystalline melt basalt (ICMB), and the matrix in a polished section of DaG 262. The feldspathic and ICMB clasts have low contents of trapped Ar compared with that in the matrix. The feldspathic clast shows a wide range of ages from 3.0 to 1.7 Ga similar to those obtained by stepped heating. The younger age is interpreted as a minimum age for the last major event that assembled this meteorite. The ICMB shows two age clusters at 3.37 and 3.07 Ga, where the older age may be that of the impact event that formed the impact melt. Several cosmic‐ray exposure (CRE) ages were obtained as expected for a polymict regolith breccia. The CRE ages are 106 and 141 Ma for the feldspathic clast and the ICMB, respectively. One of the feldspathic fragments, DaG‐2, shows a range between 200–400 Ma. These CRE ages, which are similar to those determined for returned samples of the lunar regolith, indicate that the different components of DaG 262 experienced preexposure prior to assemblage of the meteorite.     

Analysis of the pipe depth development in small-scale backward erosion piping experiments

Acta Geotechnica - Backward erosion piping is an important failure mechanism for water-retaining structures. It results in the formation of shallow pipes at the interface of a sandy or silty...     

Uranium removal from groundwater using hydroxyapatite

The present work shows that U can be effectively removed from groundwater using permeable reactive barriers with hydroxyapatite (HAP) as reactive material. The main factor influencing the removal processes is the composition of the groundwater, namely the concentration of Ca and carbonate. Sorption of U onto the HAP surface seems to be the dominant removal process with the possibility of remobilisation. Newly formed U-phosphate minerals were detected by ESEM/EDX and XRD in samples with high U content indicating either a dissolution-precipitation mechanism or sorption onto the apatite surface followed by alteration of the structure. The formed U-phosphate minerals are stable under common groundwater conditions and can be remobilised only at high pH-values and high carbonate concentrations.     

Shakemaps uncertainties and their effects in the post-seismic actions for the 2012 Emilia (Italy) earthquakes

The May 20, 2012, Emilia Ml 5.9 earthquake was followed by some major aftershocks, well recorded by a large number of temporary stations that were installed to monitor the sequence. These additional recordings allowed us a thorough testing of the performance of the ShakeMap—a procedure designed to provide rapid information on the experienced ground motion. We found that the shakemaps for the May 29, 2012, Ml 5.8 earthquake, obtained using the permanent stations only, underestimate significantly the ground motion computed with the highest station density, especially for PSA at long periods (T \(=\) 3.0 s). This low-frequency motion is controlled primarily by the surface waves recorded in the Po plain: the observed site effects are likely not accounted properly by the site correction coefficient based on Vs30 as implemented in the ShakeMap procedure. The shakemaps determined during the seismic sequence have been included in an Italian national law that was passed after the 2012 earthquake. According to this law, the factories safety verifications were bound to the comparison between the shakemaps and the design acceleration required by the current national seismic code. We then decide to appraise the impact of the shakemap accuracy on the law provisions. Following the law recommendations, we have estimated the possible errors resulting from the incomplete evaluation of the ground shaking: our results show that, if the complete dataset were available at the time of the law approval, the number of buildings for which the safety check was required would have been significantly smaller.     

Subsidence Modeling Validation Through Back Analysis for an Italian Gas Storage Field

The multi-disciplinary work described in the paper was aimed at analyzing and predicting the cyclical ground surface movements induced by underground gas storage (UGS) activities in a depleted gas field located in the Po Plain (Italy). The field has been operated as a storage facility for nearly three decades. Currently, the possibility of delta-pressuring the reservoir (i.e. to increase the maximum operating pressure above the initial reservoir pressure) to enhance the storage performance is being considered. Significant information was collected over time: 2/3D seismic surveys, geological and sedimentological studies, 60+ logged wells, geotechnical lab tests and 50+ years of production history and monitoring were available for the development of a fully integrated static–dynamic–geomechanical analysis. The mechanical aspects of the study are the focus of this paper. The data coming from different sources at different scales were analysed and integrated to set up and characterize a 3D finite element method mechanical model to calculate the surface movements induced by UGS activity by adopting an elasto-plastic constitutive law. The model was then calibrated via a back analysis approach, i.e. the model parameters were fine-tuned so that the simulated subsidence/uplift would compare satisfactorily with the ground movements collected over nearly 10 years of monitoring via interferometric synthetic aperture radar analysis in the region under investigation. Eventually, the calibrated model was used as a forecasting tool for subsidence evaluation under different future storage strategies, including delta-pressuring conditions. Results proved that no significant subsidence is expected even if the maximum operating pressure reached 120 % of the initial formation pressure.     

Changes in ostracod assemblages and morphologies during lake‐level variations of Lago Cardiel (49°S), Patagonia,Argentina, over the last 15.6 ka

Changes in the ostracod assemblages from two sediment cores collected from Lago Cardiel in southeastern Patagonia (49°S) reflect the main regional abrupt climatic changes over the last 15.6 cal. ka BP. Shifts in species abundance and switches in dominances suggest that these were mainly driven by variable salinity. During the Late Pleistocene, Limnocythere rionegroensis was abundant and dominant, indicating waters with high salinity and prevalence of evaporative processes. Between 12.6 and 10.8 cal. ka BP, Lago Cardiel expanded markedly and reached an Early Holocene highstand of +55 m above present lake level. A major change in ostracod assemblage in which Limnocythere patagonica appears as the dominant species in parallel with the disappearance of L. rionegroensis and Eucypris aff. cecryphalium mirrored this transitional period between the cold and dry Late Pleistocene and the humid and warm Early Holocene. Over the last 4 cal. ka BP, L. rionegroensis returned to the species assemblage and Riocypris whatleyi increased its abundance pointing towards increasing salinities. The variations in size, shape and ornamentation of L. rionegroensis and R. whatleyi fossil valves were examined using geometric morphometric techniques and further compared to those of modern Patagonian sites. Limnocythere rionegroensis specimens displayed high morphological variability during the evolution of Lago Cardiel. More specifically, the switch in reproductive mode – from sexual to parthenogenetic– and the increase in valve ornamentation around 12.7 cal. ka BP suggest that these changes were promoted by the hydrological alteration that occurred in the Late Pleistocene. This exercise provides a robust range of morphological variation for these proxies, which will be useful in further taxonomic and palaeoenvironmental studies adding more information about different factors influencing the observed morphological trends.     

Compensating for estimation smoothing in kriging

Smoothing is a characteristic inherent to all minimum mean-square-error spatial estimators such as kriging. Cross-validation can be used to detect and model such smoothing. Inversion of the model produces a new estimator—compensated kriging. A numerical comparison based on an exhaustive permeability sampling of a 4-ft² slab of Berea Sandstone shows that the estimation surface generated by compensated kriging has properties intermediate between those generated by ordinary kriging and stochastic realizations resulting from simulated annealing and sequential Gaussian simulation. The frequency distribution is well reproduced by the compensated kriging surface, which also approximates the experimental semivariogram well—better than ordinary kriging, but not as well as stochastic realizations. Compensated kriging produces surfaces that are more accurate than stochastic realizations, but not as accurate as ordinary kriging.