New finding suggests ‘super-Earth’ may be lifeless after all

Astronomers have discovered several candidates of so called “super-Earth,” potentially habitable planets outside solar system, raising anticipation to find extraterrestrial life forms.

However, new study indicates such planets may be dry despite ideal distance to their stars.

According to a research published on Space.com, Alien planets might experience tidal forces powerful enough to remove all their water, leaving behind hot, dry worlds like Venus.

Liquid water is considered the key element of determining weather a planet is habitable, because life exists virtually wherever there is liquid water on Earth.

Previously, starlight has been considered to be the key condition for existence of liquid water. Too far from a star, and the lack of light makes a world too cold, freezing all its water; too close to a star, and all that blazing heat makes a world too hot, boiling all of its water off in what is known as a runaway greenhouse effect.

Venus is the perfect example of such effect, where solar radiation broke up all of Venus's vaporized water into hydrogen and oxygen, which leaked away from the planet entirely.

Nevertheless, scientists are now saying Tidal heating can also trigger runaway greenhouse effect, making “tidal Venuses.”

Effects of tidal falls significantly with distance, which means tidal Venuses do not occur around stars as massive as our sun.

But around dimmer and smaller stars -- less than a third the mass of our sun – and failed or dead stars known as dwarf stars, it is possible for a tidal wave to completely dry out liquid water the starlight has failed to vaporize.

The problem is these dwarf star systems are where many of potentially habitable planets were discovered, because their dim nature means their habitable zones are theoretically very close.

Earlier this month, it has been reported a planet around a star known as GJ 667C was new best candidate to support liquid water and potentially life.

However, GJ 667C is also an M-class dwarf star, meaning it is also a candidate to producing tidal Venuses.

After a tidal Venus loses all its water and becomes uninhabitable, the tides could alter its orbit so that it no longer experiences tidal heating. As such, it might no longer appear like a tidal Venus, but look just like any other world in its star's habitable zone, fooling researchers into thinking it is potentially friendly for life, even though it has essentially been sterilized.

Scientists are hoping by factoring these findings, they can waste less time on observing dry worlds.

“As candidates for habitable worlds are found, tidal effects need careful attention,” Rory Barnes, a planetary scientist and astrobiologist at the University of Washington said. “You don’t want to waste time on desiccated planets.”

On the other hand planetary scientist Norman Sleep at Stanford University, who did not take part in this research, suggests some positive effects of tidal heat in finding habitable planets.

Sleep says it could be that instead of triggering a runaway greenhouse effect, tidal heating might actually warm otherwise frigid planets enough for them to have liquid water on their surface.

“Whether or not something could stay habitable or not through this mechanism is unclear to me,” he cautioned.