Extreme Tilts Make Planets Uninhabitable

The list of conditions that need to be met for a planet to be considered habitable is now one item larger. Experts say that even exoplanets located in their stars' habitability zones may not be inhabitable if their axis have extreme tilts, such as Uranus'.

On Earth, a tilt of 23+ degrees, achieved more than 600 million years ago, is associated with the emergence of complex life forms. Before that time, extreme axial tilts caused equally extreme seasons, which displayed massive temperature variations between months.

This is the primary consequence of weird tilts. At this point, for most of the world, temperature differences between summer and winter are around 50 to 60 degrees Celsius. All organisms living in a given habitat are now evolved to handle these variations.

But life may have not had such an easy time developing, were it not for the break it got so long ago. In other words, it's possible for life to evolve and adapt to an environment, but a lot more difficult for it to emerge in an unsuited one, Space reports.