Study finds an exoplanet, tilted on its side, could still be habitable if covered in ocean

NEW research shows that planets covered in water could support life under conditions previously thought impossible.

22/04/2009 WIRE: This handout illustration released on April 21, 2009 by the European Southern Observatory (ESO) shows the p...

SCIENTISTS have long believed that a factor in the habitability potential of an exoplanet (a planet that does not revolve around the sun but rather its own star) is the angle of its axis relative to its orbit around the parent star.

The angle of a planet’s axis is called its obliquity and until now the thinking has been that even if the planet resides in the habitable zone, if it tilts mostly on its side, it would be unable to support life.

Earth, for instance, has quite a low obliquity of 23.5Ëš and thus as our planet completes a daily rotation almost all the surface area gains direct exposure to sunlight as well as having a break at night. This allows for the surface temperature to even out — like a pig on a spit.

Alternatively if a planet has a higher obliquity (such as Uranus’s 98Ëš) and has a pole directly facing the parent star, it is thought that one side would be in perpetual sunlight for half the year with the opposite side remaining freezing cold.

This series of images from NASA's Hubble Space Telescope shows how the ring system around the distant planet Uranus appears at ever more oblique (shallower) tilts as viewed from Earth, culminating in the rings being seen edge-on in three observing opportunities in 2007. The best of these events appears in the far right image taken with Hubble's Wide Field Planetary Camera 2 14/08/2007.

However a new model indicates that life could survive such conditions provided that the planet was covered in ocean.

Published in Icarus, the study was conducted by researchers at MIT and could have interesting implications on planetary research.

One of the lead researchers, David Ferreira, said the findings of the study were at odds with their expectation that conditions on such a planet “would basically boil, and freeze, which would be really tough for life,” he said in a press release.

“We found that the ocean stores heat during summer and gives it back in winter, so the climate is still pretty mild, even in the heart of the cold polar night. So in the search for habitable exoplanets, we’re saying, don’t discount high-obliquity ones as unsuitable for life.”

Nearly 2,000 planets beyond our solar system have been identified to date and with the initial findings of this MIT study, it appears that the potential for life could be much greater than previously thought.