This story appears in the February 2013 issue of National Geographic magazine ... parts of the body they couldn’t otherwise see, satellite images help scientists find and map long-lost rivers ...

This story appears in the June 2017 issue of National Geographic magazine. Order prints of select National Geographic photos at NationalGeographicArt.com.

Photograph by Garcia Julien, Getty Images We also enjoy protection from Earth's magnetic field ... such as the Transiting Exoplanet Survey Satellite, are poised to find even more.