Water in the universe

Much of the universe's water may be produced as a byproduct of star formation. When stars are born, their birth is accompanied by a strong outward wind of gas and dust. When this outflow of material eventually impacts the surrounding gas, the shock waves that are created compress and heat the gas. The water observed is quickly produced in this warm dense gas.[13]

Water has been detected in interstellar clouds within our galaxy, the Milky Way. Water probably exists in abundance in other galaxies, too, because its components, hydrogen and oxygen, are among the most abundant elements in the universe. Interstellar clouds eventually condense into solar nebulae and solar systems such as ours.

Water vapor is present on:

* Mercury - 3.4% in the atmosphere, and large amounts of water in Mercury's exosphere[14]
* Venus - 0.002% in the atmosphere
* Earth - trace in the atmosphere (varies with climate)
* Mars - 0.03% in the atmosphere
* Jupiter - 0.0004% in the atmosphere
* Saturn - in ices only
* Enceladus (moon of Saturn) - 91% in the atmosphere
* exoplanets known as HD 189733 b[15] and HD 209458 b.[16]

Liquid water is present on:

* Earth - 71% of surface
* Moon - small amounts of water have been found (in 2008) in the inside of volcanic pearls brought from Moon to Earth by the Apollo 15 crew in 1971.[17] NASA reported the detection of water molecules by NASA's Moon Mineralogy Mapper aboard the Indian Space Research Organization's Chandrayaan-1 spacecraft in September 2009.[18]

Strong evidence suggests that liquid water is present just under the surface of Saturn's moon Enceladus and on Jupiter's moon Europa where it may exist as a 100km deep ocean covering the whole moon which would amount to more water than is in all the Earth's oceans.

Water ice is present on:

* Earth - mainly as ice sheets
* polar ice caps on Mars
* Titan
* Europa
* Enceladus
* Comets and comet source populations (Kuiper belt and Oort cloud objects).

Water ice may be present on the Moon, Ceres, and Tethys. Water and other volatiles probably comprise much of the internal structures of Uranus and Neptune.