For a planetary surface to boast extensive areas of both land and water, a delicate balance must be struck between the volume of water it retains and the capacity of its oceanic basins. Each of these two quantities may vary substantially across the full spectrum of water-bearing worlds. Why the Earth's values are so well balanced is an unresolved and long-standing conundrum. In a paper published in the Monthly Notices of the Royal Astronomical Society the author, Fergus Simpson of the Institute of Cosmos Science at the University of Barcelona, has constructed a statistical model -- based on Bayesian probability -- to predict the division between land and water on habitable exoplanets.
This model predicts that most habitable planets are dominated by oceans spanning over 90% of their surface area (95% credible interval). This conclusion is reached because the Earth is in close proximity to the waterworld limit, a regime where the existence of our species would no longer be viable. "A scenario in which the Earth has less water than most other habitable planets would be consistent with results from simulations, and could help explain why some planets have been found to be a bit less dense than we expected" explains Simpson.
To read more, click here.