This document provides a summary of the key facts about the planets in our solar system in 3 sentences or less per planet: Mercury has no substantial atmosphere and its surface has been shaped by impact cratering, volcanism, and tectonic activity. Venus rotates slowly in the opposite direction of most planets and has a dense carbon dioxide atmosphere that causes powerful greenhouse effect. Earth's atmosphere protects us from radiation, its axial tilt causes seasons, and its magnetic field is generated by its liquid iron core.