The gravitational signature of Martian volcanoes

By modeling the elastic flexure of the Martian lithosphere under imposed loads, we provide a systematic study of the old and low-relief volcanoes (>3.2 Ga, 0.5 to 7.4 km) and the younger and larger prominent constructs within the Tharsis and Elysium provinces ( 3.2 Ga, 0.5 to 7.4 km) and the younger and larger constructs clustered in the Tharsis and Elysium provinces (<3 Ga, 5.8 to 21.9 km). The observed topography is used to define the load and to derive a simulated gravity field that is compared to the observed gravity. The bulk density of the lava that composes all volcanoes is found to be 3,200 kg/m 3 , which is representative of iron-rich basalts as sampled by the Martian basaltic meteorites. The elastic part of the lithosphere, that is, the part maintaining loads over geologic time, is found to have been thin when the small, old volcanoes formed, which implies that the lithosphere was hot early in geologic history. Conversely, larger volcanoes are found to have been emplaced on a cold and thicker elastic lithosphere.