January 6, 2015

A gas giant planet rising over the horizon of an alien waterworld. New research shows that oceans on super-Earths, once established, can last for billions of years. (Credit: David A. Aguilar/CfA)

Chuck Bednar for redOrbit.com Your Universe Online

One of the key factors in the search for life on other worlds is a planets ability to sustain liquid water, and researchers from the Harvard-Smithsonian Center for Astrophysics (CfA) have for the first time revealed that this possibility exists on the type of planets known as super-Earths.

Super-Earths, which are extrasolar planets that have a mass higher than Earths but one well below that of smaller gas giants such as Uranus and Neptune, could support oceans similar to those found on our planets for billions of years once they were established, the CfA researchers said Monday at a meeting of the American Astronomical Society (AAS).

When people consider whether a planet is in the habitable zone, they think about its distance from the star and its temperature, lead author Laura Schaefer explained in a statement. However, they should also think about oceans, and look at super-Earths to find a good sailing or surfing destination.

While water covers 70 percent of the planet we call home, it actually makes up a small percentage of the overall bulk of the planet, the CfA researchers explain. The Earth is primarily made of rock and iron, and only about one-tenth of it is water.

However, liquid H2O isnt just found on the Earths surface, as research has shown that there is several oceans worth of water contained in the mantle as well, they noted. That water was pulled underground by plate tectonics and subduction of the seafloor, and if not for the H2O returning to the surface through volcanism, the planets oceans would essentially vanish.

This planet-wide recycling process helps the Earth maintain its oceans, so Schaefer and her colleagues turned to computer simulations to see if similar processes would also take place on super-Earths. They found that planets between two and four times the mass of Earth did an even better job of establishing and maintaining massive bodies of water than our homeworld.

In fact, the CfA research team found that the oceans of super-Earths would persist for a period of at least 10 billion years unless they were boiled away from an evolving red giant star.

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Super-Earths capable of maintaining oceans of liquid water