Map of Mars' gravity illuminates planet's interior

Martian gravity map
A Martian gravity map showing the Tharsis volcanoes and surrounding flexure. The white areas in the center are higher-gravity regions produced by the massive Tharsis volcanoes, and the surrounding blue areas are lower-gravity regions that may be cracks in the crust (lithosphere).
MIT/UMBC-CRESST/GSFC via NASA