Water Worlds May be Too Wet for Life

Earth-sized planets with deep global oceans may not be able to stabilize their climates, and will end up either too hot or too cold for life.

Ocean planets may not be able to maintain a climate for life

Artist's impression of Kepler-69c, a planet that might be a potential water world. (NASA Ames/JPL-Caltech/T.Pyle)
Water, we think, is an essential ingredient for life, or at least any kind of life we might imagine. But it may be possible to have too much of a good thing. In new work, Dr. Daniel Kitzmann, a Post-doctoral Fellow at the Physics Institute and Centre for Space and Habitability at the University of Bern in Switzerland, and his colleagues, have investigated the dynamics of "water worlds."

These are planets, roughly similar in size to the Earth, but with no land, and with oceans perhaps more than 100km deep. They've found that on worlds like this, a unique form of "hot ice" forms at the extreme pressures under their oceans, which seals off the planetary core from the ocean and atmosphere. This prevents the formation of the kind of carbon cycle that exists on Earth, which exchanges CO2 between the rocky core, the ocean and the atmosphere.

This carbon cycle works to regulate temperatures on Earth, preventing things from getting too hot or too cold. But on a water world, this "thermostat" can't exist, and without perfect conditions, these planets will become super-hot or freeze solid, and thus be much less hospitable for life.

Related Links

Paper in Monthly Notices of the Royal Astronomical Society
Science news article
Q&A with Daniel Kitzmann