Earth and planets
Planets are natural products of star formation and provide laboratories where gravity, geology, atmospheres, chemistry and—in at least one case—life interact.
Solar SystemThe Sun, planets, moons, asteroids and comets form a gravitationally bound planetary system.
EarthEarth is differentiated into core, mantle, crust, oceans and atmosphere and is geologically active.
Planet formationPlanets form from material in disks around young stars.
ExoplanetsThousands of planets around other stars show that planetary systems are common and diverse.
HabitabilityLiquid water, long-term energy sources, atmospheric conditions and planetary history help define environments suitable for life.