Chemical studies on the possible existence of life on Mars.

Although there is no direct evidence yet for the existence of life on Mars, it is reasonable to conclude that the emergence of life on Earth, which appears to have been controlled by universal laws of physics and chemistry, may have been repeated elsewhere in the universe. The dual approach of synthesis and analysis in our experimental studies has provided ample evidence in support of this hypothesis.     

The observational data base on the motion and evolution of comets and asteroids

Current observational data base on the motion of comets and asteroids is reviewed. Particular attention is paid to the absolute and relative abundances of different dynamical types of objects, and to the time intervals between their first and last observations. The latter quantity, ranging from two days to two milliennia for individual objects, is the dominant measure of the accuracy of the orbit determination. Distribution of the tracking times of comets (distinguished by dynamical age: new, long-period, Halley type, Jupiter family) and asteroids (distinguished by stability: Apollos, Amors, main-belt asteroids, outer librators, outer unstable objects) are reconstructed. The peculiar shapes of individual distributions can be explained by the complex mechanisms of discoveries, rediscoveries, orbit computations, follow-up observations and backward identifications. A comparison is also made with the dynamical data base on meteoroids, as regards the accuracy of their orbits.The cumulative tracking times (170000 yr for all 7600 objects with known orbits taken together) are compared with the lifetimes and occurrence rates of different events of evolutionary significance. Only in the case of short-period comets the evolution is rapid enough to render observable a variety of important changes, ranging from drastic transformations of orbits to disruption or total outgassing. For asteroids, only minor cratering collisions which do not result in detectable changes of their orbits are covered by the whole observational history.Expected future improvements of observing and data-handling techniques are outlined. With these in view, the size and character of the data to become available by the end of this century are predicted. Dynamical types of objects, which are currently known in only one or a few examples, are pointed out. Apparently, other types of rare occurrence and short survival time still escape detection. A list of easiest targets of short-duration spacecraft missions is presented.The deficiencies of current statistics due to observational selection; the broad variety of regimes of motion occupied by widely differing proportional representations of the known objects; and demands for suitable targets of future spacecraft missions make it highly desirable to maintain the present rapid rate of augmentation of the data base for the years to come.Recent passages of two comets — 1983d IRAS-Araki-Alcock and 1983e Sugano-Saigusa-Fujikawa — near the Earth indicate that both the collision rate given in Table VIII and the contribution of long-period comets to it may have been slightly underestimated. The appropriate adjustment of the log-t values by less than — 0.10 has no effect of the general conclusions, however.The success of the orbiting observatory IRAS in detecting faint interplanetary objects lends better promises for the increase of the number of known objects (in particular comets) than anticipated in Section 6 and estimated in Table IX. Obviously, the outcome will largely depend on the implementation, time coverage and degree of exploitation of similar projects in the near future.     

The Deep Impact Earth-Based Campaign

Prior to the selection of the comet 9P/Tempel 1 as the Deep Impact mission target, the comet was not well observed. From 1999 through the present there has been an intensive world-wide observing campaign designed to obtain mission critical information about the target nucleus, including the nucleus size, albedo, rotation rate, rotation state, phase function, and the development of the dust and gas coma. The specific observing schemes used to obtain this information and the resources needed are presented here. The Deep Impact mission is unique in that part of the mission observations will rely on an Earth-based (ground and orbital) suite of complementary observations of the comet just prior to impact and in the weeks following. While the impact should result in new cometary activity, the actual physical outcome is uncertain, and the Earth-based observations must allow for a wide range of post-impact phenomena. A world-wide coordinated effort for these observations is described.     

Recent advancements in the EST project

The European Solar Telescope (EST) is a project of a new-generation solar telescope. It has a large aperture of 4?m, which is necessary for achieving high spatial and temporal resolution. The high polarimetric sensitivity of the EST will allow to measure the magnetic field in the solar atmosphere with unprecedented precision. Here, we summarise the recent advancements in the realisation of the EST project regarding the hardware development and the refinement of the science requirements.     

Trojans in habitable zones

With the aid of numerical experiments we examined the dynamical stability of fictitious terrestrial planets in 1:1 mean motion resonance with Jovian-like planets of extrasolar planetary systems. In our stability study of the so-called "Trojan" planets in the habitable zone, we used the restricted three-body problem with different mass ratios of the primary bodies. The application of the three-body problem showed that even massive Trojan planets can be stable in the 1:1 mean motion resonance. From the 117 extrasolar planetary systems only 11 systems were found with one giant planet in the habitable zone. Out of this sample set we chose four planetary systems--HD17051, HD27442, HD28185, and HD108874--for further investigation. To study the orbital behavior of the stable zone in the different systems, we used direct numerical computations (Lie Integration Method) that allowed us to determine the escape times and the maximum eccentricity of the fictitious "Trojan planets."     

Linear and circular structures of the Bohemian Massif — Comparison of satellite and geophysical data

Two structural schemes of the Bohemian Massif are presented and compared. The first one is a result of interpretation of various geophysical data and the second one is compiled on the basis of decoding of space imagery from different sources (Kosmos, Landsat etc.). Both schemes have many structural features in common, but there are diversities namely in the hierarchy of directions and regional distribution of linear structures. These problems are discussed in detail. For example, the most impressive system of structures is the NW-SE system in both schemes, whereas the NE-SW is more remarkable in the geophysical scheme; the N-S and the E-W systems are best expressed in the scheme of photolineaments. These facts are due to the genesis, age, development and dynamic characteristics of respective structural systems. The circular structural features namely those of large size are mostly remarkable in space imagery. At present, they are not distinguished genetically but only described regionally.     

Wind-field analysis on the basis of METEOSAT images

A method for the determination of cloud motion vectors is proposed by calculating from METEOSAT images the displacement of characteristic formations in the brightness field. The claculations are made for a sector of the Atlantic Ocean (ψ = 48°?38°N, λ = 24°?12°W). The adaptability of the Soebel operator for such calculations is also shown. The calculated wind vectors are in a good agreement with wind data at 850 mb surface.     

NeQuick 2 and IRI Plas VTEC predictions for low latitude and South American sector

Using vertical total electron content (VTEC) measurements obtained from GPS satellite signals the capability of the NeQuick 2 and IRI Plas models to predict VTEC over the low latitude and South American sector is analyzed. In the present work both models were used to calculate VTEC up to the height of GPS satellites. Also, comparisons between the performance of IRI Plas and IRI 2007 have been done. The data correspond to June solstice and September equinox 1999 (high solar activity) and they were obtained at nine stations. The considered latitude range extends from 18.4°N to ?64.7°N and the longitude ranges from 281.3°E to 295.9°E in the South American sector. The greatest discrepancies among model predictions and the measured VTEC are obtained at low latitudes stations placed in the equatorial anomaly region. Underestimations as strong as 40?TECU [1?TECU?=?10¹⁶?m^?2] can be observed at BOGT station for September equinox, when NeQuick2 model is used. The obtained results also show that: (a) for June solstice, in general the performance of IRI Plas for low latitude stations is better than that of NeQuick2 and, vice versa, for highest latitudes the performance of NeQuick2 is better than that of IRI Plas. For the stations TUCU and SANT both models have good performance; (b) for September equinox the performances of the models do not follow a clearly defined pattern as in the other season. However, it can be seen that for the region placed between the Northern peak and the valley of the equatorial anomaly, in general, the performance of IRI Plas is better than that of NeQuick2 for hours of maximum ionization. From TUCU to the South, the best TEC predictions are given by NeQuick2.The source of the observed deviations of the models has been explored in terms of CCIR foF2 determination in the available ionosonde stations in the region. Discrepancies can be also related to an unrealistic shape of the vertical electron density profile and or an erroneous prediction of the plasmaspheric contribution to the vertical total electron content. Moreover, the results of this study could be suggesting that in the case of NeQuick, the underestimation trend could be due to the lack of a proper plasmaspheric model in its topside representation. In contrast, the plasmaspheric model included in IRI, leads to clear overestimations of GPS derived TEC.     

Classification of Geostationary Objects

This paper lists all geostationary and near-geostationary objects contained in ESA's DISCOS database.     

Partially Ionized Plasmas in Astrophysics

Partially ionized plasmas are found across the Universe in many different astrophysical environments. They constitute an essential ingredient of the solar atmosphere, molecular clouds, planetary ionospheres and protoplanetary disks, among other environments, and display a richness of physical effects which are not present in fully ionized plasmas. This review provides an overview of the physics of partially ionized plasmas, including recent advances in different astrophysical areas in which partial ionization plays a fundamental role. We outline outstanding observational and theoretical questions and discuss possible directions for future progress.