The Martian plasma environment: electric field and Langmuir probe diagnostics

The plasma environment of Mars has been studied by a small handful of spacecraft. From the sparse observations that exist, one may conclude that the solar wind-Martian "magnetosphere" interaction is different in significant ways from the solar wind\´s interaction with Earth\´s magnetosphere. Mars offers an opportunity to make significant advances in our understanding of the fundamentals of the solar wind\´s interaction with cold celestial bodies, with suitable plasma instrumentation orbiting the planet. We briefly review what is known about Mars\´ plasma environment and address some scientific topics that can be studied by proper plasma instrumentation in Mars\´ vicinity, in particular the scientific potential of Langmuir probe measurements. Finally, we exemplify how the studies may contribute to an enhanced understanding not only of the plasma surrounding Mars, but also of the planet itself and its neutral atmosphere.