Water World . ... 16.03.1997 . ... Credit Copyright: STS-45 Crew NASA Explanation: Water (Dihydrogen Oxide, H2O) is a truly remarkable chemical compound, fundamental to life on Earth . Earth is the only planet in the Solar System where the surface temperature and pressure allow the three forms of water, solid (ice) , liquid (ocean) , and gas ( water vapor condensing in clouds ) to exist simultaneously on its surface. ... NASA Web Site Statements, Warnings, and Disclaimers . ...