article_snippet.sent: a free-floating Earth would need liquid water.'
article_snippet.sent: A planet needs to keep warm for liquid water to form, and without the sun, this heat would have to come from a free-floating Earth interior. '
article_snippet.sent: A layer of ice on a planet's surface can act as a strong insulator, locking in a planet's heat,' claims Raymond.
article_snippet.sent: If the ice layer is thick enough, then a planet can maintain an ocean of liquid water beneath the ice.'
article_snippet.sent: Dr Michael Liu of the Institute for Astronomy at the University of Hawaii calculates that the ice layer needs to be at least 10 km (6 miles) thick to prevent the ice layer from freezing for billions of years.
article_snippet.sent: Research by astrophysicists Dorian Abbot and Eric Switzer from the University of Hawaii discovered that heat would come from the breakdown of radioactive elements inside a planet's core.
article_snippet.sent: As well as internal heat, Raymond says another way a planet can keep warm is using a thick atmosphere. '
article_snippet.sent: A free-floating Earth with a thick hydrogen atmosphere could keep A free-floating Earth with a thick hydrogen atmosphere surface temperature above the freezing point of water,' writes Raymond. '
article_snippet.sent: a planet could have lakes and oceans (and possibly life) on a planet surface.'