Chuck Bednar for redOrbit.com – Your Universe Online
One of the key factors in the search for life on other worlds is a planet’s 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 Earth’s 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 isn’t just found on the Earth’s 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 planet’s 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.
However, on the largest of the planets that were studied (five times the mass of Earth), it took longer for the oceans to form – approximately one billion years, to be exact, due to a thicker crust and lithosphere that delayed the start of volcanic outgassing. This discovery suggests that the research for life should focus primarily on older super-Earths, Schaefer said.
“It takes time to develop the chemical processes for life on a global scale, and time for life to change a planet’s atmosphere. So, it takes time for life to become detectable,” said study co-author Dimitar Sasselov, also from the CfA.
“This also suggests that, assuming evolution takes place at a similar rate to Earth’s, you want to search for complex life on planets that are about five and a half billion years old, a billion years older than Earth,” the Harvard-Smithsonian center added.
—–
Follow redOrbit on Twitter, Facebook, Instagram and Pinterest.
Comments