Ceres

""The Grineer have expanded their empire into this region.""

The Grineer is the controlling faction on this planet.

The vital target of the planet is the Lieutenant Lech Kril, who has a chance to drop blueprints for the parts of the Frost Warframe. He also has a higher than average chance to drop Orokin Cell.

Trivia

 * Missions on Ceres appear to be named after different Roman/Greek-relations and/or numerous asteroids. (Needs confirmation)
 * Ceres is the only known dwarf planet in the inner solar system, and may have liquid water, which is a possibility as to why it was chosen as a planet with missions.