One of the unique characteristics of Earth which sets it apart from other known planets is its oceans. Such large bodies of surface water have not yet been found elsewhere, although a number of moons, including Europa, Enceladus and Titan and possibly others, are thought to have subsurface oceans and or seas.
As it turns out however, water oceans may be common on rocky planets, at least in their early stages of formation, according to a new study announced on March 18, 2013 at the 44th Lunar and Planetary Science Conference in The Woodlands, Texas. The results were presented by Lindy Elkins-Tanton of the Carnegie Institution for Science in Washington, D.C.
Water oceans may be a natural stage of a rocky planet’s evolution; how this affects a planet’s habitability however depends on how long those oceans last. Venus and Mars may have had oceans ealier in their history for example, but were lost later on due to changing conditions.
The process is relatively simple: the water for the oceans comes from the original material clumping together to form the planets, according to Elkins-Tanton (water from comets may be a secondary source). First, water evaporates out of the hot, molten rock which the young planet is initially composed of. The released water then forms a thick, steamy atmosphere. Later, as the planet gradually cools and hardens, that atmosphere collapses, allowing the water to collect on the surface as an ocean.
If rocky worlds tend to at least start out with oceans though, that would increase the chances of life being able to gain a foothold. “Habitability is going to be much more common than we had previously thought,” according to Elkins-Tanton.
The LPSC paper is available here.
This article was first published on Examiner.com.