The Martian crustal magnetic field: a global view from MGS and MAVEN measurements

Almost 20 years ago the Mars Global Surveyor revealed the striking magnetic figure of Mars. While devoid of an active magnetic field today, Mars possesses a remanent magnetic field which may reach several thousands of nT locally. The processes which have shaped the crustal magnetization remain largely enigmatic. During almost 7 years MGS made magnetic field measurements, mainly at a constant altitude of 400 km and at only two local times. Low-altitude measurements (below 250 km) and at several local times are very sparse and may hamper the interpretation of magnetic field models in terms of planet history or of magnetic source properties. The MAVEN mission was inserted in orbit around Mars in Sept. 2014. It flies on a very elliptical orbit, with a periapsis as low as 125 km, and it will cover all local times. In this paper we will first compare existing MGS-based models to MAVEN measurements, to check the consistency between these two different spacecrafts. Then we will present a (preliminary) model built using both MGS and MAVEN measurements. This new model uses MAG measurements by MGS and MAVEN, but also total field estimates at 185 km from MGS electron reflectometry measurements. The improvement of this new model will be discussed, and in particular how it may change our view on the crustal field of Mars.