We describe the Mars ionosphere with unprecedented detail in 3‐D, as simulated by a Mars general circulation model (the Laboratoire de Météorologie Dynamique Mars GCM), and compare it with recent measurements. The model includes a number of recent extensions and improvements. Different simulations for a full Martian year have been performed. The electron density at the main ionospheric peak is shown to vary with the Sun‐Mars distance and with the solar variability, both in the long‐term (11 year solar cycle) and on shorter temporal scales (solar rotation). The main electronic peak is shown to be located at the same pressure level during all the Martian year. As a consequence, its altitude varies with latitude, local time, and season according to the natural expansions and fluctuations of the neutral atmosphere, in agreement with previous models. The model predicts a nighttime ionosphere due only to photochemistry. The simulated ionosphere close to the evening terminator is in agreement with observations. No effort has been made to explain the patchy ionosphere observed in the deep nightside. We have compared the modeled ionosphere with Mars Global Surveyor and Mars Advanced Radar for Subsurface and Ionosphere Sounding data. The model reproduces the solar zenith angle variability of the electron density and the altitude of the peak, although it underestimates the electron density at the main peak by about 20%. The electron density at the secondary peak is strongly underestimated by the model, probably due to a very crude representation of the X‐ray solar flux. This is one of the aspects that needs a revision in future versions of the model.

Aims.This work presents a uniform and homogeneous study of chemical abundances of refractory elements in 101 stars with and 93 without known planetary companions. We carry out an in-depth investigation of the abundances of Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Na, Mg and Al. The new comparison sample, spanning the metallicity range FeH, fills the gap that previously existed, mainly at high metallicities, in the number of stars without known planets.Methods.We used an enlarged set of data including new observations, especially for the field “single” comparison stars . The line list previously studied by other authors was improved: on average we analysed 90 spectral lines in every spectrum and carefully measured more than 16 600 equivalent widths (EW) to calculate the abundances.Results.We investigate possible differences between the chemical abundances of the two groups of stars, both with and without planets. The results are globally comparable to those obtained by other authors, and in most cases the abundance trends of planet-host stars are very similar to those of the comparison sample. Conclusions.This work represents a step towards the comprehension of recently discovered planetary systems. These results could also be useful for verifying galactic models at high metallicities and consequently improve our knowledge of stellar nucleosynthesis and galactic chemical evolution.

We present the [ X/H] trends as a function of the elemental condensation temperature TC in 88 planet host stars and in a volume-limited comparison sample of 33 dwarfs without detected planetary companions. We gathered homogeneous abundance results for many volatile and refractory elements spanning a wide range of TC, from a few dozen to several hundred kelvin. We investigate possible anomalous trends of planet hosts with respect to comparison sample stars to detect evidence of possible pollution events. No significant differences are found in the behaviour of stars with and without planets. This is consistent with a “primordial” origin of the metal excess in planet host stars. However, a subgroup of 5 planet host and 1 comparison sample stars stands out as having particularly high [ X/H] vs. TC slopes.