Sampling of Mars analogue materials in a laboratory environment

Acta Geotechnica - Two laboratory test series were performed with the aim of ensuring the proper functionality of the key sampling mechanisms installed aboard the Mars rover ExoMars, currently...     

The effect of DHM resolution in computing the topographic-isostatic harmonic coefficients within the window technique

The window technique was suggested earlier to get rid of the double consideration of the topographic-isostatic masses within the data window in the framework of the remove-restore technique. Within the course of the window technique, one needs to compute the harmonic coefficients of the topographic-isostatic masses for the data window. The paper studies the effect of using Digital Height Models (DHMs) with different resolutions of the computed harmonic coefficients of the topographic-isostatic masses for the data window. Two different test areas, one in Austria and one in Egypt, are considered in this investigation. A set of DHMs with different resolutions is available for both test areas. The harmonic coefficients of the topographic-isostatic masses for the data window are computed for both test areas using the available DHMs with different resolutions. A comparison among the potential degree variances of the different DHMs is carried out. The computation of the window topographic-isostatic gravity anomalies for both data sets is performed using the set of the available DHMs with different resolutions. The results show that using a DHM with the grid size of about 5 km for smooth topography and of about 3 km for rough topography gives practically the same topographic-isostatic gravity anomalies for the data window in a significantly much less CPU time compared to that of using the finest DHM.     

Assessing impacts of invasive phytoplankton: The Baltic Sea case

There is an increasing understanding and requirement to take into account the effects of invasive alien species (IAS) in environmental quality assessments. While IAS are listed amongst the most important factors threatening marine biodiversity, information on their impacts remains unquantified, especially for phytoplankton species. This study attempts to assess the impacts of invasive alien phytoplankton in the Baltic Sea during 1980-2008. A bioinvasion impact assessment method (BPL - biopollution level index) was applied to phytoplankton monitoring data collected from eleven sub-regions of the Baltic Sea. BPL takes into account abundance and distribution range of an alien species and the magnitude of the impact on native communities, habitats and ecosystem functioning. Of the 12 alien/cryptogenic phytoplankton species recorded in the Baltic Sea only one (the dinoflagellate Prorocentrum minimum) was categorized as an IAS, causing a recognizable environmental effect.     

Discrete clay diagenesis in a very low-permeable sequence constrained by an isotopic (K–Ar and Rb–Sr) study

Multimethod analyses of several size fractions of clays were used to reconstruct the diagenetic history of the shallow buried claystones within the Paris Basin. A systematic decrease occurred in K-Ar dates relative to the decrease in size of the clay fractions, signifying higher amounts of newly formed clay material in the finer fractions. We suggest that the authigenic clay minerals occurring in the fine fractions had an Al-montmorillonite composition. By assuming that the isotopic K-Ar and Rb-Sr dates obtained on a bentonite layer in the sedimentary sequence stand for pure, authigenic clay minerals, one may interpret all K-Ar dates as mixtures of one authigenic and two detrital end-members. The results imply that a period of low sea level favoured diagenetic smectite-type clay formation about 10-15 million years after deposition of the sediments. Signatures of limited-scale chemical and isotopic homogenisation mean that the rock volumes affected by the diagenetic modifications had to be quite limited. The study of clay minerals extracted from some stylolites further suggests that any overpressure related to the origin of stylolites had no effect on clay authigenesis.     

Transportation of water,particulate and dissolved organic and inorganic matter between a salt marsh and the Ems-Dollard estuary,The Netherlands

Transport processes were studied in a gully between a salt marsh and an estuary. After storm tides, ebb currents in the gully reached high values. It is concluded that particulate matter (both organic and inorganic) are imported into the marsh. Coarse organic debris is exported during storm tides, but this amount is low when compared with the primary production on the marsh. Exports are shown for dissolved organic carbon, ammonia, phosphate and silica, while nitrate and possibly nitrite are imported. Organic matter derived from in situ production and net import is buried and partly mineralized in the marsh.     

Considerations on a suction drill for lunar surface drilling and sampling: I. Feasibility study

In this paper, we consider a drilling method, which might prove useful both for applications on the Moon and for drilling on Mars, Venus, or other planetary surfaces. It is based on the use of a cold gas flow for pumping fine-grained debris particles out of the borehole, after they have been pulverized by the bore crown. We present a basic design and demonstrate by a hydrodynamic calculation that such a system should work effectively even on an airless body like the Moon, where the driver gas has to be provided from the associated lander or rover, which acts as the bore platform.     

87Sr86Sr in Late Proterozoic carbonates: evidence for a “mantle” event at ∼900 Ma ago

Strontium isotopic measurements were made on Late Proterozoic carbonates from West African Craton. Comparison of samples with acceptable trace element patterns with coeval data from southern Africa and with the published Australian results suggests that the ${}^{87}\text{Sr}{}^{86}\text{Sr}$ ratio of the Late Proterozoic sea water evolved in the following manner about 0.7075 at 1000 ± 50 Ma, 0.7056 to 0.7074 at 900 ± 50 Ma, 0.7068 to 0.7091(0.7106) at 800 ± 50 Ma, 0.7074 to 0.7077 at 700 ± 50 Ma, and 0.7076 to 0.7089(0.7096) at 600 ± 50 Ma ago. The variations are comparable in magnitude and frequency to those described previously for the Phanerozoic. Strontium isotopic values in the radiogenic part of this range suggest that the continental river flux of Sr into Late Proterozoic oceans was of comparable isotopic composition to its present day counterpart (～0.711). Consequently, the non-radiogenic ${}^{87}\text{Sr}{}^{86}\text{Sr}$ value at ～900 ± 50 Ma ago signifies a large flux of “mantle” strontium into the ocean at this time. Because the present time resolution is only about 75 ± 25Ma, additional sampling as well as better stratigraphie resolution and more definite selection criteria are required for construction of a more detailed Late Proterozoic sea water curve.