Model computations of Schumann resonance on Titan     

Alexander P. Nickolaenko  Konrad Schwingenschuh 《Planetary and Space Science》2003,51(13):853-862

We model the global electromagnetic (Schumann) resonance in the atmosphere of Titan. Parameters of conductivity of the lower ionosphere were implemented taken from existing aeronomic models of Titan's atmosphere. Two exponential conductivity profiles were constructed: one of them suggests favorable conditions for Schumann resonance and the other models considerable attenuation in the ionospheric plasma. Peak frequencies and Q-factors of resonance were computed as well as resonance spectra for the signals arriving from individual vertical lightning discharges and from strokes uniformly distributed over the planet. The models show that detection of Schumann resonance on Titan is feasible, especially in favorable conditions. Possible applications of Schumann resonance in the studies of Titan's lightning activity are outlined.  相似文献   

Non-uniform seasonal defrosting of subpolar dune field on Mars     

Konrad J Kossacki  Jacek Leliwa-Kopystyński 《Icarus》2004,168(1):201-204

Images of the sub-polar regions of Mars show existence of various seasonal-depending features, including mosaics of dark patches called Dalmatian spots. We interpret formation of dark patches on dune fields by means of the non-uniform sublimation of winter CO₂ ice deposit.  相似文献   

Seasonal melting of surface water ice condensing in martian gullies     

Konrad J. Kossacki  Wojciech J. Markiewicz 《Icarus》2004,171(2):272-283

In this work we consider when and how much liquid water during present climate is possible within the gullies observed on the surface of Mars. These features are usually found on poleward directed slopes. We analyse the conditions for melting of H₂O ice, which seasonally condenses within the gullies. We follow full annual cycle of condensation and sublimation of atmospheric CO₂ and H₂O, accounting for the heat and mass transport in the soil. During the summer, once the facets of the gullies are exposed to the Sun the water ice can melt and evaporate. Two mid latitude locations in both hemispheres are considered. The model includes both the rough geometry of the gullies as well as the slope of the surface where the gullies appear. It is an extension of the model developed to calculate condensation of CO₂ ice in troughs of different sizes, including polygonal features on Mars (Kossacki and Markiewicz, 2002, Icarus 160, 73; Kossacki et al., 2003, Planet. Space Sci. 51, 569). We have found, that water ice accumulated during winter can undergo transition to the liquid phase after complete sublimation of CO₂ ice. The amount of liquid water depends on water content in the atmosphere and on the local wind speed. It is probably not enough to destabilise the slope and cause flow of the surface material. However, even the small amounts of liquid water predicted, can play an important role in surface chemistry, in increasing the cohesive strength of the soil's surface layer and possibly may have some exobiological implications.  相似文献   

Possible remnants of a frozen mud lake in southern Elysium, Mars     

Konrad J. Kossacki  Wojciech J. Markiewicz  David Page 《Icarus》2006,181(2):363-374

In this work we estimate the minimum persistence time of subsurface ice in water rich sediment layers remaining after sublimation of a martian lake. We simulate sublimation of ice from layers of different granulations and thicknesses. Presented results assume insolation and atmospheric conditions characteristic for the present day southern Elysium, where data from Mars Express have identified surface features possibly indicating the very recent presence of a frozen body of water [Murray et al., 2005. Nature 434, 352-356]. The age of these features is estimated to be several million years. On this time scale, we find that most of the water ice must have sublimated away, however remnant ice at a few percent level cannot be excluded. This amount of water ice is sufficient for chemical cementation of the observed features and explains their relatively pristine appearance, without significant signs of erosion.  相似文献   

40Ar/39Ar dating of the Araguainha impact structure,Mato Grosso,Brazil     

Konrad Hammerschmidt  WOLF VON Engelhardt 《Meteoritics & planetary science》1995,30(2):227-233

Abstract— Pursuing the exploration of the Araguainha impact structure (Engelhardt et al., 1992), we present ⁴⁰Ar/³⁹Ar ages (1) of biotite samples from the granite, which forms the central uplift of the structure, and (2) of a melt rock, formed by the impact. Total degassing ages of biotites from granite samples range from 326 to 481 Ma. The variation is explained by Ar losses due to the oxidation of divalent Fe and by removal of K. The K loss depends on the time that the granite was exposed to weathering at particular outcrops. The oldest age of the least oxidized biotite from a granite sample, collected at a site most recently exposed, signifies that the ascending granite passed the 300° isotherm earlier than 481 Ma ago. Early Devonian Furnas sandstones, the oldest sediments exposed by the impact, were deposited on this granite basement 410–396 Ma ago. The ⁴⁰Ar/³⁹Ar analyses of two size fractions of an impact melt rock, resulting in plateau ages of 245.5 ± 3.5 Ma and 243.3 ± 3.0 Ma, respectively, indicate that the Araguainha impact occurred close to the Permian-Triassic boundary.  相似文献   

Results of statistical analysis of primary components concentrations in bulk chemical composition of ordinary chondrite groups     

Tadeusz A. Przylibski  Magdalena Długosz-Lisiecka  Katarzyna Łuszczek  Konrad Blutstein 《Meteoritics & planetary science》2023,58(9):1246-1259

We used two different methods of statistical analysis—cluster analysis and principal component analysis—to analyze the concentrations of principal chemical components (Si, Mg, Ca, Fe, Ni) and Co in ordinary chondrites. The analysis is based predominantly on published data (metadata). In total, chemical composition data from 646 ordinary chondrites were used in the statistical analysis. The aim of this analysis was to establish whether it would be possible or not to distinguish H, L, and LL chondrites based on the concentrations of major elements and Co in their bulk chemical compositions. It was also important to determine what conclusions such an analysis could enable to draw about matter differentiation in the formation environments of primordial parent bodies of particular ordinary chondrite groups (H, L, and LL). Another aim of the statistical analysis was to determine whether the distribution of Fe and Ni (with Co admixtures) is independent of petrographic types within particular groups of chondrites. This is of crucial importance for determining the distribution of FeNi(Co) ore occurrences in potential extraterrestrial deposits on modern asteroids—the sources of ordinary chondrites. The obtained results of statistical analyses confirmed that a clear-cut distinction between particular groups of ordinary chondrites is only possible for group H, while distinguishing L chondrites from LL chondrites is not always obvious. The results of the statistical analyses relating to the question of the possible existence of several primordial parent bodies (formation environments) of each group of ordinary chondrites are consistent with the results of contemporary astronomical spectroscopy research. What is particularly interesting is obtaining indications of the existence of common formation environments of the matter of L and LL chondrites, possibly on a few primordial parent bodies. The statistical analyses indicate that there is no correlation between the concentration of principal chemical components and the petrographic type of ordinary chondrites. This proves homogenous distributions of these elements within the parent bodies of each group of ordinary chondrites. Hence, the distribution of these elements in individual present-day asteroids is also homogenous.  相似文献   

Speciation leads to divergent methylmercury accumulation in sympatric whitefish     

Nanina Blank  Alan G. Hudson  Pascal Vonlanthen  Ole Seehausen  Chad R. Hammerschmidt  David B. Senn 《Aquatic Sciences - Research Across Boundaries》2013,75(2):261-273

Central European lake whitefish (Coregonus spp.) colonized Swiss lakes following the last glacial retreat and have undergone rapid speciation and adaptive radiation. Up to six species have been shown to coexist in some lakes, and individual species occupy specific ecological niches and have distinct feeding and reproductive ecologies. We studied methylmercury (MeHg) accumulation in sympatric whitefish species from seven Swiss lakes to determine if ecological divergence has led to different rates of MeHg bioaccumulation. In four of seven lakes, sympatric species had distinctly different MeHg levels, which varied by up to a factor of two between species. Generally, species with greater MeHg levels were smaller in body size and planktivorous, and species with lower MeHg were larger and benthivorous. While modest disparities in trophic position between species might be expected a priori to explain the divergence in MeHg, δ¹⁵N of bulk tissue did not correlate with fish MeHg in five of seven lakes. Results of a nested ANCOVA analysis across all lakes indicated that only two factors (species, lake) explained substantial portions of the variance, with species accounting for more variance (52 %) than inter-lake differences (32 %). We suggest that differences in MeHg accumulation were likely caused by diverging metabolic traits between species, such as differences in energy partitioning between anabolism and catabolism, potentially interacting with species-specific prey resource utilization. These results indicate substantial variability in MeHg accumulation between closely related fish species, illustrating that ecological speciation in fish can lead to divergent MeHg accumulation patterns.  相似文献   

Thermal convection in the porous methane-soaked regolith in Titan: Finite amplitude convection     

Leszek Czechowski  Konrad J. Kossacki 《Icarus》2012,217(1):130-143

Titan is the only body, beside the Earth, where liquid is present on the surface. This paper is aimed to show the properties of possible convection in a porous regolith on Titan. In our previous work (Czechowski, L., Kossacki, K.J. [2009]. Icarus 202, 599–607) we showed, that the Rayleigh number Ra can exceed its critical value Ra_c. Hence, the convective motion of liquid filling pores in the regolith is likely for Titan relevant parameters. In the present work we investigate the properties of finite amplitude convection, i.e. for Ra > Ra_cr. We study the basic properties of the steady state solution, the Nusselt number, the density of the heat flow and the average temperatures. Evolution of the convection is also considered. We conclude that any reasonable thermal model of Titan’s regolith should take into account the possibility of the considered convection. We discuss also possibility of identification of this convection (or its consequences in the form of evaporates) by the Cassini and possible future spacecrafts.  相似文献   

Variable infiltration and river flooding resulting in changing groundwater quality – A case study from Central Europe     

Konrad Miotliński  Dieke Postma  Andrzej Kowalczyk 《Journal of Hydrology》2012

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Recovery of Injected Freshwater from a Brackish Aquifer with a Multiwell System   总被引：2，自引：0，他引：2  

Konrad Miotliński  Peter J. Dillon  Paul Pavelic  Karen Barry  Sarah Kremer 《Ground water》2014,52(4):495-502

Herein we propose a multiple injection and recovery well system strategically operated for freshwater storage in a brackish aquifer. With the system we call aquifer storage transfer and recovery (ASTR) by using four injection and two production wells, we are capable of achieving both high recovery efficiency of injected freshwater and attenuation of contaminants through adequately long residence times and travel distances within the aquifer. The usual aquifer storage and recovery (ASR) scheme, in which a single well is used for injection and recovery, does not warrant consistent treatment of injected water due to the shorter minimum residence times and travel distances. We tested the design and operation of the system over 3 years in a layered heterogeneous limestone aquifer in Salisbury, South Australia. We demonstrate how a combination of detailed aquifer characterization and solute transport modeling can be used to maintain acceptable salinity of recovered water for its intended use along with natural treatment of recharge water. ASTR can be used to reduce treatment costs and take advantage of aquifers with impaired water quality that might locally not be otherwise beneficially used.  相似文献