Investigating the influences of open crustal magnetic field regions on the Martian Ionosphere

The hunt for life in the solar system is intimately linked to the search for water, found in abundance on Earth, but relatively scarce on the other “Earth-like” planets in our solar system (i.e. Venus and Mars). Given their broadly similar densities and distances from the Sun, it is likely that the Earth-like planets were all formed from broadly similar material in the early solar nebula and that the currently observed differences are a result of the differing long-term evolution of each planet. In the case of Mars, the cessation of a magnetic dynamo and the resulting collapse of the planet’s main magnetic field about 4 billion years ago are thought to have been major factors in the loss of atmospheric volatiles, such as water and carbon dioxide. This is due to the shielding effect a planetary magnetic field confers to the atmosphere and surface environment. The Earth’s magnetic field typically holds the solar wind at a distance of around ten planetary radii from the atmosphere and ionosphere. However, in the case of Mars, the absence of a significant magnetic field has allowed the solar wind direct access the atmosphere/ionosphere and resulted in the loss of volatiles (such as water) from the planetary environment to interplanetary space.

This study will investigate the interaction between regions of strong crustal magnetic field near the surface of Mars (remnants of Mars’ original magnetic field) and the solar wind. In regions where the crustal field is oriented roughly vertically, the solar wind can gain access to the atmosphere and ionosphere, where it is thought to cause heating. This heating is likely to be responsible for bulges observed in the Martian ionosphere over regions of strong near-vertical crustal field by the Mars Express spacecraft and may result in upwelling “fountains” of atmospheric material. This material can then interact with the solar wind and be removed from the Martian atmosphere, contributing to the continuing erosion of Mars’ atmosphere. The proposed research will be accomplished using numerical modelling techniques first used to study the near-Earth space environment and applying them to the very different atmosphere, ionosphere and magnetic field of Mars. A computer model will be developed to solve time-dependent equations of continuity, momentum and energy balance along simplified cusp-like magnetic field lines for the densities, field-aligned fluxes and temperatures of a number of ion species and electrons common in the Martian ionosphere.

The outcomes of this research can be validated by comparison with data returned from Mars orbiting spacecraft (e.g. ESA’s Mars Express) and will have important implications for the forthcoming Mars exploration missions (including ExoMars), the evolution of the Martian environment and broader studies of exobiology.