Tidal friction could facilitate 'habitable situations' on distant 'Earth-sized planets': NASA

A new computer model by NASA has found that friction from tides could help some distant Earth-sized planets, traveling in dangerous orbits, to create habitable situations.

The findings were consistent with observations that Earth-sized planets appear to be very common in other star systems. Although heat could be a destructive force for some planets but the right amount of friction, and therefore heat, could be helpful in surviving.

Wade Henning, a University of Maryland scientist working at NASA's Goddard Space Flight Center in Greenbelt, Maryland, said that these planets would often experience just enough friction to move them out of harm's way and into safer, more-circular orbits more quickly than previously predicted.

Simulations of young planetary systems indicated that giant planets often upset the orbits of smaller inner worlds. Even if those interactions weren't immediately catastrophic, they could leave a planet in a treacherous eccentric orbit, a very elliptical course that raises the odds of crossing paths with another body, being absorbed by the host star, or getting ejected from the system.

Another potential peril of a highly eccentric orbit was the amount of tidal stress a planet might undergo as it draws very close to its star and then retreats away. Near the star, the gravitational force is powerful enough to deform the planet, while in more distant reaches of the orbit; the planet could ease back into shape and this flexing action produces friction, which generates heat.

An additional way for a terrestrial planet to achieve high amounts of heating would be to cover in a very thick ice shell, similar to an extreme "snowball Earth." and it was also found that some planets could move into a safer orbit about 10 to 100 times faster than previously expected.

The study is published online in the Astrophysical Journal.