Planets having odd tilts could be habitable

A new modeling done by researchers has suggested that pivoting planets that lean one way and then change orientation within a short geological time period might be surprisingly habitable.

Shawn Domagal-Goldman, an astrobiologist at NASA's Goddard Space Flight Center in Greenbelt, Md, said planets like these are far enough from their stars that it would be easy to write them off as frozen, and poor targets for exploration, but in fact, they might be well-suited to supporting life.

The new modeling considers planets that have the same mass as Earth, orbit a sun-like star and have one or two gas giants orbiting nearby. In some cases, gravitational pulls from those massive planets could change the orientation of the terrestrial world's axis of rotation within tens to hundreds of thousands of years - a blink of an eye in geologic terms.

John Armstrong of Weber State University in Ogden, Utah, led the team, which includes Barnes, Domagal-Goldman, and other colleagues.

The team ran thousands of simulations for planets in 17 varieties of simplified planetary systems. The models the researchers built allowed them to adjust the tilt of the planetary orbits, the lean in the axes of rotation, and the ability of the terrestrial planet's atmosphere to let in light.

In some cases, tilted orbits can cause a planet to wobble like a top that's almost done spinning - and that wobbling should have a big impact on the planet's glaciers and climate. Earth's history indicates that the amount of sunlight glaciers receive strongly affects how much they grow and melt. Extreme wobbling, like that seen in some models in this study, would cause the poles to point directly at the sun from time to time, melting the glaciers. As a result, some planets would be able to maintain liquid water on the surface despite being located nearly twice as far from their stars as Earth is from the sun.

The habitability concept has been explored in a paper published in the journal Astrobiology.