Los exoplanetas de tamaño similar al de la Tierra tienen en su mayoría agua en grandes cantidades.https://buff.ly/2vSoqCy
Water-worlds are common: Exoplanets may contain vast amounts of water -- ScienceDaily: Scientists have shown that water is likely to be a major component of those exoplanets (planets orbiting other stars) which are between two to four times the size of Earth. It will have implications for the search of life in our Galaxy.