Origin of Comet Nuclei and Dynamics

We present a review of the main physical features of comet nuclei, their birthplaces and the dynamical processes that allow some of them to reach the Sun’s neighborhood and become potentially detectable. Comets are thought to be the most primitive bodies of the solar system although some processing—for instance, melting water ice in their interiors and collisional fragmentation and reaccumulation—could have occurred after formation to alter their primordial nature. Their estimated low densities (a few tenths g?cm^?3) point to a very fluffy, porous structure, while their composition rich in water ice and other highly volatile ices point to a formation in the region of the Jovian planets, or the trans-neptunian region. The main reservoir of long-period comets is the Oort cloud, whose visible radius is ～3.3×10⁴ AU. Yet, the existence of a dense inner core cannot be ruled out, a possibility that would have been greatly favored if the solar system formed in a dense galactic environment. The trans-neptunian object Sedna might be the first discovered member that belongs to such a core. The trans-neptunian population is the main source of Jupiter family comets, and may be responsible for a large renovation of the Oort cloud population.     

Fine structure of the interplanetary shock front according to measurements of the ion flux of the solar wind with high time resolution

According to the data of the BMSW/SPEKTR-R instrument, which measured the density and velocity of solar wind plasma with a record time resolution, up to ~3 ×10^–2 s, the structure of the front of interplanetary shocks has been investigated. The results of these first investigations were compared with the results of studying the structure of the bow shocks obtained in previous years. A comparison has shown that the quasi-stationary (averaged over the rapid oscillations) distribution of plasma behind the interplanetary shock front was significantly more inhomogeneous than that behind the bow-shock front, i.e., in the magnetosheath. It has also been shown that, to determine the size of internal structures of the fronts of quasi-perpendicular (θ_BN > 45°) shocks, one could use the magnetic field magnitude, the proton density, and the proton flux of the solar wind on almost equal terms. A comparison of low Mach (М _А < 2), low beta (β₁ < 1) fronts of interplanetary and bow shocks has shown that the dispersion of oblique magnetosonic waves plays an essential role in their formation.     

Narrative psychological content analysis as a tool for psychological status monitoring of crews in isolated,confined and extreme settings

This paper is about a pilot application of narrative psychological content analysis in the psychological status monitoring of Crew 71 of a space analog simulation environment, the Mars Desert Research Station (MDRS). Both the method and its theoretical framework, Scientific Narrative Psychology, are original developments by Hungarian psychologists [5] (László, 2008). The software was NooJ, a multilingual linguistic development environment [11] (Silberztein, 2008). Three measures were conceptualized and assessed: emotional status, team spirit and subjective physical comfort. The results showed the patterns of these three measures on a daily basis at group level, and allowed for detecting individual differences as well. The method is adaptable to languages involved in space psychology, e.g. Russian, French and German in addition to English.     

Effect of gravity on the velocity of a crystallization front

The crystal growth from a liquid can be studied by methods of non-equilibrium thermodynamics of a discontinuity surface. These methods are used to derive the dependence of the crystalization velocity on transport and surface phenomena across and along an interface solid-liquid and on the acceleration of gravity.     

A method for estimating cross radiance

When imaging the surface from satellites or aircraft, “cross radiance” diminishes the information content of the pictures. In this paper a simple method is presented to estimate the value of cross radiance. This method includes a height-dependent aerosol size distribution model and the calculations refer to the single scattering approximation. The height variation of aerosol size distribution has significant effect on the value of cross radiance, while the areal distribution does not change much in comparison with that of the height-independent aerosol model.     

Unusually Distant Bow Shock Encounters at Mars: Analysis of March 24, 1989 Event

Detailed analysis of disturbances observed on 24 March, 1989 far upstream of the usual Martian bow shock position was completed with the use of the planetary obstacle and bow shock models relevant for the period of Phobos 2 observations and for low Mach numbers, respectively. It is proven that the system of discontinuities observed in the solar wind between 18:42 and 19:36 UT was the consequence of unusually distant planetary bow shock excursions. The cause was unusually small ρV ² and M _a values in the solar wind flow.     

Tírez lake as a terrestrial analog of Europa

Tírez Lake (La Mancha, central Spain) is proposed as a terrestrial analogue of Europa's ocean. The proposal is based on the comparison of the hydrogeochemistry of Tírez Lake with the geochemical features of the alteration mineralogy of meteoritic precursors and with Galileo's Near Infrared Mapping Spectrometer data on Europa's surface. To validate the astrobiological potential of Tírez Lake as an analog of Europa, different hydrogeochemical, mineral, and microbial analyses were performed. Experimental and theoretical modeling helped to understand the crystallization pathways that may occur in Europa's crust. Calculations about the oxidation state of the hypothetical Europan ocean were estimated to support the sulfate-rich neutral liquid model as the origin of Europa's observed hydrated minerals and to facilitate their comparison with Tírez's hydrogeochemistry. Hydrogeochemical and mineralogical analyses showed that Tírez waters corresponded to Mg-Na-SO(4)-Cl brines with epsomite, hexahydrite, and halite as end members. A preliminary microbial ecology characterization identified two different microbial domains: a photosynthetically sustained community represented by planktonic/benthonic forms and microbial mat communities, and a subsurficial anaerobic realm in which chemolithotrophy predominates. Fluorescence in situ hybridization has been used to characterize the prokaryotic diversity of the system. The subsurficial community seemed to be dominated by sulfate-reducing bacteria and methanogens. Frozen Tírez brines were analyzed by Fourier-transform infrared techniques providing spectra similar to those reported previously using pure components and to the Galileo spectral data. Calorimetric measurements of Tírez brines showed pathways and phase metastability for magnesium sulfate and sodium chloride crystallization that may aid in understanding the processes involved in the formation of Europa's icy crust. The use of fluorescence hybridization techniques for microbial detection and characterization in hypersaline environments makes this methodology strongly advisable for future Europa astrobiological missions.