NASA's Kepler space telescope celebrated its 1,000th exoplanet discovery earlier this month, an impressive milestone in the search for life on other worlds.
Now astronomers are homing in on those exoplanets that may have liquid water, which is thought to be essential for supporting life. And according to new research, so-called "super-Earths" may host vast oceans that last for billions of years.
A super-Earth is an extrasolar planet whose mass is greater than Earth's but smaller than that of gas giants like Neptune and Uranus.
Earth's mantle holds vast amounts of water, which returns to to the surface through volcanism. Since this "recycling" process is crucial for maintaining our planet's oceans, researchers from the Harvard-Smithsonian Center For Astronomy (CfA) wondered if a similar process might occur on super-Earths.
What did they find? Super-Earths between two and four times Earth's mass seem to be even better than Earth at establishing and maintaining oceans. In fact, the water on these planets could last for at least 10 billion years, the research suggested.
The finding may give astronomers one more thing to consider when figuring out which exoplanets are likeliest to harbor extraterrestrial life, according to Laura Schaefer, a CfA graduate student and the leader of the research effort.
"When people consider whether a planet is in the habitable zone, they think about its distance from the star and its temperature," Schaefer said at a press conference. "However, they should also think about oceans, and look at super-Earths to find a good sailing or surfing destination."
The findings were presented in Seattle on Jan. 8 at the annual meeting of the American Astronomical Society.