Newfound planet ‘Gliese 163 c’ may host alien life in massive ocean

Scott Sutherland

Discovered earlier this month by the High Accuracy Radial velocity Planet Searcher (HARPS) at the La Silla Observatory in Chile, and confirmed last Thursday, the exoplanet Gliese 163 c is now ranked as one of the top contending exoplanets to have alien life.

One of two known planets orbiting Gliese 163, a red dwarf star 49 light years away in the constellation Dorado, Gliese 163 c, a 'super Earth' with nearly 7 times the mass of our planet, orbits within its star's 'habitable zone' — the region around the star where liquid water can exist on the planet's surface — which is one of the criteria that we believe is needed for life to develop. The other planet detected in the system, Gliese 163 b, is even larger than Gliese 163 c, orbits even closer to its star, and goes around in its orbit once every 9 days. Indications are that there may be one other planet in the system, but researchers have not been able to confirm its existence yet.

Due to a red dwarf star's small size, the habitable zone it creates is much closer to it than the habitable zone generated by our Sun. So, even though both Gliese 163 c and Earth orbit just inside the habitable zone of their respective star, Gliese 163 c is nearly ten times closer to its star than Earth is to the Sun, well within the orbit of Mercury, and circles Gliese 163 every 26 days.

The researchers still don't know much about the Gliese 163 c other than its mass and orbital distance.

"We do not know for sure that it is a terrestrial planet," says Xavier Bonfils, of France's Joseph Fourier University-Grenoble, according to "Planets of that mass regime can be terrestrial, ocean, or Neptune-like planets."

If it is a terrestrial planet, like Earth, with a similar composition, it could have a surface temperature of around 60 degrees Celsius — compared to an average temperture of 15 degrees Celsius on Earth — and may have a diameter up to twice as large as the Earth's and a surface gravity of about 2 to 3 times that which we experience here.

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Abel Mendez, a Professor of Physics and Astrobiology at the University of Puerto Rico at Arecibo, and the principle investigator at the Planetary Habitability Laboratory (PHL), suggested the possibility that Gliese 163 c may be an ocean world, with a thick atmosphere about 10 times more dense than ours, and a global ocean under a pink, cloud-covered sky. He and his colleagues at PHL use basic comparisons with Earth, and a bit of imagination, to determine what conditions may be like on distant worlds.

PHL currently has a list of 6 potential habitable exoplanets, each with an 'Earth Similarity Index' (ESI) rating between 0.0 and 1.0, with 1.0 being exactly like Earth.

#6 on the list, but the first on the list to be discovered, Gliese 581 d has an ESI of 0.72.

#5 is now occupied by recently-discovered Gliese 163 c, with an ESI of 0.73.

#4 is HD 85512 b, discovered roughly a year ago, with an ESI of 0.77.

#3 is Kepler-22 b, with an ESI of 0.81, which was discovered last December.

#2 is Gliese 667C c, discovered orbiting one of the stars of a triple-star system last November, with an ESI of 0.85.

Finally, still at #1 since its discovery in September of 2010, is Gliese 581 g, with an ESI of 0.92.

Scientists at PHL consider planets with an ESI of between 0.6 and 0.8 to be roughly like Mars, meaning that they could support simple forms of life like microbes. Planets above 0.8 are, as a general rule, considered to be Earth-like, meaning that Kepler-22 b, Gliese 667C c and Gliese 581 g are likely to be very similar to Earth.

There is a small chance that Gliese 163 c may transit across its star from our vantage point, which would allow us to get far more information about its composition and atmosphere, but until then we will have to be content with speculation, at least until researchers can discover another way to get that kind of information at this distance.

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