One would think, despite the strangely haunting sequence of monstrous waves ripping and chewing spacecraft and human bodies alike, that extraterrestrial planets covered in water would be prime life supporting material. One might even go so far as to suppose that–considering the degree to which water is both necessary and nearly sufficient to support any kind of carbon-based life–that an ocean world should actually be preferred to one covered with land or archipelago.
WATER WORLD HOPEFULS TO GO DAUNTED
According to new research published online before in print in the Monthly Notices of the Royal Astronomical Society, that’s not the case. Water that totally covers the surface of a planet interacts with carbon dioxide in the atmosphere in ways that are capable of turning chilly planets frigid and warm ones even hotter. This recent research shows that Earth-sized water worlds would be habitable in an extremely limited range of temperatures; from roughly 32 to 260 degrees Fahrenheit. Any world slipping outside of that range is liable to be detrimental to primordial forms of life. The bad news is that these sub- and super-temps are actually quite common among planets inhabiting the “Goldilocks zone,” which, for a G2 star like our sun, places a planet roughly 102 million to 140 million miles from its star.
For comparison, the Earth is 93 million miles away from the sun.
INTERSTELLAR REALITY CHECK
When temperatures fall below freezing, the ocean water decomposes more carbon dioxide, a greenhouse gas of obvious portent, which reduces the planet’s temperature, and at higher temperatures, less carbon dioxide is absorbed, causing the ocean to release a much greater amount of carbon dioxide, which sets a planet into a runaway warming period (hence the term greenhouse effect).
WIDER IMPLICATIONS
This supposition sketches scenarios for water worlds whose type falls outside that of Earth-sized planets and Sun-like stars. Researchers involved in this study have added that the process would be very similar for larger worlds orbiting even more gigantic stars.
The same cycle would take place with greenhouse gases like methane. With such thin temperature range necessary for habitability, ocean planets unfortunately are not likely to make the splash we might have hoped they would as we explore our interstellar neighborhood for signs of life.
