Scientists believe Neptune-like planets could support life

A selection of scientists have introduced the concept that small gas planets, similar to Neptune, could be discovered in the near future and made habitable. Their research was published in the January 15 issue of Astrobiology. It demonstrates methods by which computer models predict when and where gas planets may support life.

Various conditions must be met in order to make life possible on a Neptune-like planet.  Researchers at the University of Washington insist that tidal forces and vigorous stellar activity are the two most important ones. The gas planets orbit low-mass stars called M dwarfs that are much smaller and dimmer than the Sun. As a result, their habitable zones are closer.

Because of this, forces that are much weaker on Earth can have a dramatic effect on a gas planet’s habitability. Stellar activity, such as gamma rays emitted from young M dwarfs is inhospitable to life on nearby planets. Tidal force is the gravitational pull that a star exerts on surrounding planets. The Earth’s moon exerts a similar force on the Earth, though it is weaker.

“This is the reason we have ocean tides on Earth, as tidal forces from both the moon and the sun can tug on the oceans, creating a bulge that we experience as a high tide,” said University of Washington doctoral student Rodrigo Luger. “Luckily, on Earth it’s really only the water in the oceans that gets distorted, and only by a few feet. But close-in planets, like those in the habitable zones of M dwarfs, experience much stronger tidal forces.”

The proposed gas planets are usually found far away from their host stars and are very cold.However, if one is pulled into the star’s habitable zone by a tidal force, exposure to much higher gamma and ultraviolet radiation will occur. This can cause the gas to disperse, leaving behind a gas free planet within the habitable zone.

“Such a planet is likely to have abundant surface water, since its core is rich in water ice,” Luger said. “Once in the habitable zone, this ice can melt and form oceans.”

The scientists stress that, while these conditions form a basis for life, many others must be met.

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