The hydrologic cycle is another global-scale system and involves flow of water and other materials among the atmosphere, land, and ocean reservoirs. Earth is also increasingly viewed as a planet with limited resources, such as fossil fuels and soils, and one that can be significantly modified by mankind. For example, burning fossil fuels introduces carbon dioxide into the environment. Subsequent greenhouse processes may raise Earth's average surface temperature by several degrees over the next couple of decades. The global view of Earth has been driven in part by the space-borne exploration of Earth's companions, including the Moon, Mars, and Venus, and the satellites of the outer planets.
Planetary science focuses on the study of the origin and evolution of solar system objects.
Work in this field ranges from isolating and studying interplanetary dust particles in meteorites, to understanding how Uranus's satellite Miranda has been repeatedly broken apart by impact and reassembled by accretion, to testing the hypothesis that Venus has plate tectonics.