Physical and Mechanical Properties of Lunar and Planetary Soils

Earth, Moon, and Planets -     

Observing system experiments over the Atlantic Ocean with the REMO ocean data assimilation system (RODAS) into HYCOM

Ocean Dynamics - The Oceanographic Modeling and Observation Network (REMO) focuses on scientific and technological development of operational oceanography in Brazil considering both numerical...     

Supersubstorms during Storms of September 7–8, 2017

Geomagnetism and Aeronomy - The development of two supersubstorms (i.e., very intense substorms with an amplitude of more than 2000 nT) recorded in the main phase of two consecutive strong magnetic...     

Classification issues within ensemble-based simulation: application to surge floods forecasting

The paper proposes a high-level conceptual and technological approach to manage the ensemble-based simulation, taking into account changing states of both simulated system and system of models. The approach includes systematization of ensemble-based modeling and simulation techniques, analysis of simulation results, quality assessments, and detailed analysis of ensemble management procedures using classification operators. The technological basis for such an approach includes ensemble-based simulation techniques using domain-specific software combined within a composite application; data science approaches for analysis of available datasets (simulation data, observations, situation assessments, etc.). Within this work, a set of case studies is addressed to examine the opportunities provided by the developed approach considering ensemble-based simulation of storm surges for flood prediction in St. Petersburg, Russia as an example.     

Relaxation time distribution from time domain induced polarization measurements

We propose an algorithm for inverting time domain induced polarization data to a relaxation time distribution. The algorithm is based on the (Tikhonov) regularized solution of the 1^st kind Fredholm integral equation. We test the algorithm on synthetic data, and show its robustness for a noise level, typical of laboratory time domain measurements. We also show that, for the inversion purpose, the time domain data must be obtained with the different current wavelengths. We then test the algorithm on the experimental data recently obtained on brine-saturated medium-grained quartz sand (average grain diameter of 4 × 10⁻⁴ m), and on sand mixtures. For the medium-grained sand, relaxation time distribution contains a main peak at 25 s. Different amounts (3%, 8% and 12%) of fine-grained quartz sand (average grain diameter of 1.12 × 10⁻⁴ m) were added to the medium-grained quartz sand. For the sand mixture, an additional peak is observed in the relaxation time distributions, in the time range from 1.0 to 2.5 s. The magnitude of the second peak increases with the increase of the fine-grained sand content. Therefore, the experimental data show that peaks in the relaxation time distributions are related to the grain size. On the basis of the known peak location, and of the known grain size value, we obtained the values of the diffusion coefficient, which were found to be of the same order of magnitude as those in the bulk solution.     

Suitability of biogenic carbonate of Lithospermum fruits for C dating

Lithospermum (Boraginaceae) belongs to a small group of plant taxa that accumulate biogenic carbonate in their fruits. In this genus, carbonate incrustations form in the cells of the epidermis and sclerenchyma of the pericarp. Fossil Lithospermum fruits (nutlets) with well-preserved calcified tissues commonly occur in Quaternary sediments and cultural layers. We tested the suitability of biogenic carbonate of Lithospermum fruits for radiocarbon dating using a total of 15 AMS measurement results from four modern and 11 fossil samples. The ¹⁴C data from modern samples suggest that Lithospermum utilises only atmospheric carbon to synthesise calcite in the nutlets. In general, the ages determined through ¹⁴C dating of fossil fruitscorresponded well with the absolute-age intervals for archaeological sites over the last 5000 yr. Biogenic carbonate of Lithospermum fruits, like that of Celtis, represents a new source of chronological information for late Quaternary studies.     

NMR relaxation measurements of biofouling in model and geological porous media

Recently 2D nuclear magnetic resonance (NMR) relaxation techniques have been able to access changes in pore structures through surface and diffusion based relaxation measurements. This research investigates the applicability of these methods for measuring pore and surface changes due to biofilm growth in various model porous systems and natural geological media. Model bead packs of various construction containing 100 μm borosilicate and soda lime glass beads were used to demonstrate how changes in the measured relaxation rates can be used to non-invasively verify and quantify biofilm growth in porous media. However significant challenges are shown to arise when trying to implement the same techniques to verify biofilm growth in a natural geological media.     

Development and testing of subsurface sampling devices for the Beagle 2 lander

For planetary landing missions, the capability to acquire samples of soil and rock is of high importance whenever complex analyses (e.g. isotopic studies) on these materials are to be carried out, or when samples are to be returned to Earth. Not only surface samples are of relevance, but in recent concepts at least for Mars landing missions also subsurface samples are required. Subsurface material on Mars is believed to have been protected from the inferred oxidants at the immediate surface while also being protected from the UV influx. Therefore, there is considerable hope that in subsurface soil samples on Mars, at least organic matter delivered by meteorites may be detected, and possibly also relics of earlier simple microbial life on the planet. Likewise, samples from the inside of Martian surface rocks promise to have been protected from weathering and for the same reason they are important for organic chemistry studies. In this paper, an overview is given of the development and science of two different subsurface sampling devices for the Beagle 2 lander of ESA's Mars Express mission, being a “Mole” subsurface soil sampler and a small rock coring and sampling mechanism. Besides their sampling function, both the Mole and the Corer/Grinder will provide data on physical properties of Martian soils and rock, respectively, through the way they interact with the sampled materials. Details of the Mole and Corer/Grinder design are presented, along with results of recent tests with prototypes in the laboratory on physically analogous sample materials.     

Convergence of Liapunov series for Huygens–Roche Figures

According to the classical theory of equilibrium figures, surfaces of equal density, potential and pressure concur (let us call them isobars). Isobars can be represented by means of Liapunov power series in small parameter q, up to the first approximation coinciding with the centrifugal to gravitational force ratio at the equator. Liapunov has proved the existence of the universal convergence domain: the above mentioned series converge for all bodies (satisfying a natural condition that the density ρ decreases from the center to the surface) if |q| < q*. Using Liapunov’s algorithm and symbolic manipulation tools, we have found q*= 0.000370916. Evidently, the convergence radius q* may be much greater in common situations. To comfirm it it is reasonable to consider two limiting and one or two intermediate cases for the density behaviour: ρ is a constant, the Dirac’s δ-function, linear function of the distance from the center, etc. And indeed, in the previous paper we find a three orders of magnitude greater value for homogeneous figures. In the present paper we find that in the opposite case of Huygens-Roche figures (a point-mass surrounded by a weightless atmosphere) the convergence radius is unexpectedly large and coincides with the well-known biggest possible value q*= 0.541115598 for such a class of figures. To ascertain it we ought to use numerical calculations, so our main result is demonstrated by means of a computer assisted proof. This revised version was published online in July 2006 with corrections to the Cover Date.     

The compressibility of Fe- and Al-bearing phase D to 30 GPa

High-pressure in situ X-ray diffraction experiment of Fe- and Al-bearing phase D (Mg_0.89Fe_0.14Al_0.25Si_1.56H_2.93O₆) has been carried out to 30.5 GPa at room temperature using multianvil apparatus. Fitting a third-order Birch–Murnaghan equation of state to the P–V data yields values of V ₀ = 86.10 ± 0.05 ų; K ₀ = 136.5 ± 3.3 GPa and K′ = 6.32 ± 0.30. If K′ is fixed at 4.0 K ₀ = 157.0 ± 0.7 GPa, which is 6% smaller than Fe–Al free phase D reported previously. Analysis of axial compressibilities reveals that the c-axis is almost twice as compressible (K _c  = 93.6 ± 1.1 GPa) as the a-axis (K _a  = 173.8 ± 2.2 GPa). Above 25 GPa the c/a ratio becomes pressure independent. No compressibility anomalies related to the structural transitions of H-atoms were observed in the pressure range to 30 GPa. The density reduction of hydrated subducting slab would be significant if the modal amount of phase D exceeds 10%.