Meteoric ions in the atmosphere of Mars

The effect of the metallic concentration in meteoric material in the Martian ionosphere has been investigated with the scope of exploring the possible existence of meteoric ionospheric layers as it occurs on Earth. We have calculated the ion and neutral deposition of the most abundant metals in meteoroids, iron, magnesium and silicon, and modeled their ion-neutral chemistry in order to estimate the concentration of neutral and ionic metals and electrons. We found that a low ionospheric metallic layer due to meteoric ablation is created at around 80 km, well below the main maximum at 125–135 km produced during the daytime by photoionization and photoelectron impact. Daytime and nighttime models have been developed and the effect of solar activity, and seasonal variations has also been explored. This meteoric layer is mainly formed of Mg+ and Fe+ with a magnitude of the order of 104 cm−3 at noon and decreases by two orders of magnitude during the night. The study of this lower part of the Martian ionosphere is very important in the context of the future missions, especially regarding the HF radio wave sounding technique that will be used onboard Mars Express and Nozomi spacecraft in 2004–2005.