so the pressures in the planet are lower and the interior is less densely compressed. mars has an internal structure similar to that of the Earth. A thin crust,35 km thick in the northern hemisphere and 80 km thick in the southern hemisphere, surrounds a rocky mantle whose rigidity decreases with depth as the internal temperature increases. The planet has a dense core 1500-1800 km in radius, thought to be composed of iron with a relatively large fraction of sulfur. Minute perturbations of the orbit of Mars Surveyor, caused by deformations of Mars due to solar tides, have provided more detailed information about the internal structure. They indicate that, like the Earth, Mars probably has a solid inner core and fluid outer core that is, however, too small to generate a global magnetic field.