Using spacecrafts' orbital irregularities to "see" beyond the surface of Mars. A new map of Mars' gravity made with three NASA spacecraft is the most detailed to date, providing a revealing glimpse into the hidden interior of the Red Planet. "Gravity maps allow us to see inside a planet, just as a doctor uses an X-ray to see inside a patient," said Antonio Genova of the Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts. "The new gravity map will be helpful for future Mars exp