Sand and Dust on Mars

Mars is a planet of high scientific interest. Various studies are currently being made that involve vehicles that have landed on Mars. Because Mars is known to experience frequent wind storms, mission planners and engineers require knowledge of the physical and chemical properties of Martian windblown sand and dust, and the processes involved in the origin and evolution of sand and dust storms

Temperature effects on the 15-85-micron spectra of olivines and pyroxenes

Far-infrared spectra of laboratory silicates are normally obtained at room temperature even though the grains responsible for astronomical silicate emission bands seen at wavelengths >20 micron are likely to be at temperatures below ~150 K. In order to investigate the effect of temperature on silicate spectra, we have obtained absorption spectra of powdered forsterite and olivine, along with two orthoenstatites and diopside clinopyroxene, at 3.5+-0.5 K and at room temperature (295+-2K). To determine the changes in the spectra the resolution must be increased from 1 to 0.25 cm^-1 at both temperatures since a reduction in temperature reduces the phonon density, thereby reducing the width of the infrared peaks. Several bands observed at 295 K split at 3.5 K. At 3.5 K the widths of isolated single bands in olivine, enstatites and diopside are ~ 90% of their 295 K-widths. However, in forsterite the 3.5-K-widths of the 31-, 49- and 69-micron bands are, respectively, 90%, 45% and 31% of their 295 K widths. Due to an increase in phonon energy as the lattice contracts, 3.5-K-singlet peaks occur at shorter wavelengths than do the corresponding 295-K peaks; the magnitude of the wavelength shift increases from \~ 0-0.2 micron at 25 micron to ~0.9 micron at 80 micron. Changes in the relative absorbances of spectral peaks are also observed. The temperature dependence of lambda_pk and bandwidth shows promise as a means to deduce characteristic temperatures of mineralogically distinct grain populations. In addition, the observed changes in band strength with temperature will affect estimates of grain masses and relative mineral abundances inferred using room-temperature laboratory data.Comment: 11 pages, 7 figures including figures 3a and 3b. includes latex and eps files. Accepted by MNRAS on 15th March 200

Effects of UV-organic interaction and Martian conditions on the survivability of organics

This work was funded by the Leverhulme Trust (RPG-2015-071). Dr. C. Cousins also wishes to acknowledge funding from the Royal Society of Edinburgh. This work was financed by FEDER - Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020 - Operacional Programme for Competitiveness and Internationalisation (POCI), and by Portuguese funds through FCT - Fundação para a Ciência e a Tecnologia in the framework of the project POCI-01-0145-FEDER-029932 (PTDC/FIS-AST/29932/2017).Exogenous organic molecules are delivered to the surface of Mars annually, yet their fate is largely unknown. Likewise, the survivability of putative organic biomarkers directly implicates current Mars surface exploration ambitions. Among these, amino acids are valuable target molecules due to their abiogenic and biological origins. We present the fundamental, but not previously considered, factors that affect the fate of amino acids embedded in Mars mineral analogues when exposed to ionising radiation. Using existing experimental datasets, we show that the attenuation coefficient at 200 nm for amino acids is an effective parameter for quantifying organic survivability, especially when mineral shielding is limited or absent. Conversely, the dielectric constant of a material is a potential key parameter regarding mineral shielding, as it accounts for iron content, and the physical properties of the material (pore size, surface area or water content). Finally, we combine Martian climatic parameters (surface temperature and atmospheric opacity) to show that the relative UV environment varies significantly on Mars as a function of latitude, providing a reference point for future Mars simulation studies.PostprintPeer reviewe

Effects of humidity on sand and dust storm attenuation predictions based on 14 GHz measurement

Several models were proposed to predict the attenuation of microwave signals due to sand and dust storms. Those models were developed based on theoretical assumptions like Rayleigh approximation, Mie equations or numerical methods. This paper presents a comparison between attenuation predicted by three different theoretical models with measured attenuation at 14 GHz. Dielectric constant of dust particles is one of the important parameter in prediction models. This constant is estimated from measured dust samples and is utilized for predictions. All models are found largely underestimating the measurement. Humidity is also monitored and has been observed higher during dust storm. Hence dielectric constants are re-estimated with relative humidity conditions using available conversion model. The prediction has a great impact of humidity and predicted attenuations are found much higher in humid than dry dust condition. However, all models underestimate the measurement even considering 100% of relative humidity. Hence it is recommended to investigate the models by considering humidity and other environmental factors that change during dust storm

Modelling the local and global cloud formation on HD 189733b

Context. Observations suggest that exoplanets such as HD 189733b form clouds in their atmospheres which have a strong feedback onto their thermodynamical and chemical structure, and overall appearance. Aims. Inspired by mineral cloud modelling efforts for Brown Dwarf atmospheres, we present the first spatially varying kinetic cloud model structures for HD 189733b. Methods. We apply a 2-model approach using results from a 3D global radiation-hydrodynamic simulation of the atmosphere as input for a detailed, kinetic cloud formation model. Sampling the 3D global atmosphere structure with 1D trajectories allows us to model the spatially varying cloud structure on HD 189733b. The resulting cloud properties enable the calculation of the scattering and absorption properties of the clouds. Results. We present local and global cloud structure and property maps for HD 189733b. The calculated cloud properties show variations in composition, size and number density of cloud particles which are strongest between the dayside and nightside. Cloud particles are mainly composed of a mix of materials with silicates being the main component. Cloud properties, and hence the local gas composition, change dramatically where temperature inversions occur locally. The cloud opacity is dominated by absorption in the upper atmosphere and scattering at higher pressures in the model. The calculated 8{\mu}m single scattering Albedo of the cloud particles are consistent with Spitzer bright regions. The cloud particles scattering properties suggest that they would sparkle/reflect a midnight blue colour at optical wavelengths.Comment: Accepted for publication (A&A) - 21/05/2015 (Low Resolution Maps

Microwave roasting of pyrite tailings and pyrite ash for sponge iron production

Iron ores containing ferrous minerals and sulphide minerals are specifically as several times active in microwave. Pyrolysis of the coal usually requires iron minerals for activation step to both absorption microwave from the matrix of the sulphides and conduct the heat to coal for pyrolysis. In this investigation, the copper pyrite and coal pyrite was microwave roasted to oxidize both the sulphides and even the pyrolysis of coal for reduction iron oxide. The effects were investigated by gravimetric and infrared analysis and the microwave absorption characteristics were quantified by determining the permittivities. The microwave heating behaviour studies showed that the sample temperature increased with increasing incident microwave power, processing time and sample mass. Due to the activity of the iron ore to the microwaves, a low incident power of 600W was found to be sufficient for roasting, as higher powers resulted in sintering and melting of the concentrate. The copper pyrite weight loss values after roasting were over 25% and these were similar to those obtained by conventional roasting. The main advantages of microwave roasting were that both the total pyrolysis rates and the heating rates were higher and the specific energy consumptions were lower than in coal pyrite. In this study; low-grade iron ore and sponge iron pyrite by high production of waste parched areas were carried out. X-ray diffraction analysis of the products mineralogy and grain size in polarizing microscopic description is determined by the nature of the leaching effect on the physical and chemical parameters. Chemical properties making preliminary tests to determine the pellet roasting conditions, reactivity were investigated. This assay has been determined to be advantageous in the metal results in the production of sponge iron with the pyrite ash waste. The feasibility use of low-grade iron ore with microwave roasted pyrite, and pyrite ash in production sponge iron were tested and the physical, chemical properties of the products regarding the results of microwave roasting tests were determined by examining the difference between the textural properties of the different pyrite and ash. The pyrites of Ergani copper concentrator and Siirt were in this study identified as potential iron source in terms of the basic qualifications of sponge iron

Optical constants of refractory oxides at high temperatures

Many cosmic dust species, among them refractory oxides, form at temperatures higher than 300 K. Nevertheless, most astrophysical studies are based on the room-temperature optical constants of solids, such as corundum and spinel. A more realistic approach is needed for these materials, especially in the context of modeling late-type stars. We aimed at deriving sets of optical constants of selected, astrophysically relevant oxide dust species with high melting points. A high-temperature-high-pressure-cell and a Fourier-transform spectrometer were used to measure reflectance spectra of polished samples. For corundum (alpha-Al$_2$O$_3$), spinel (MgAl$_2$O$_4$), and alpha-quartz (SiO$_2$), temperature-dependent optical constants were measured from 300 K up to more than 900 K. Small particle spectra were also calculated from these data. All three examined oxides show a significant temperature dependence of their mid-IR bands. For the case of corundum, we find that the 13$\mu$m emission feature - seen in the IR spectra of many AGB stars - can very well be assigned to this mineral species. The best fit of the feature is achieved with oblate corundum grains at mean temperatures around 550 K. Spinel remains a viable carrier of the 13$\mu$m feature as well, but only for T < 300 K and nearly spherical grain shapes. Under such circumstances, spinel grains may also account for the 31.8$\mu$m band that is frequently seen in sources of the 13$\mu$m feature and which has not yet been identified with certainty.Comment: Astronomy & Astrophysics, accepted, 26 February 2013. Article with 18 pages and 15 figure