Earth's oceans have been around for about 4 billion years, but they've changed a lot since the early millennia when they covered the whole planet and harbored methane-loving microbes. On a super-Earth, however, oceans might persist for more than twice as long — with intriguing results.
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A group of researchers led by Laura Schaefer of the Harvard-Smithsonian Center for Astrophysics have been running powerful simulations of super-Earths. Using data from known super-Earths, which are rocky, Earthlike planets that are much larger than our own, they tried to figure out what oceans would be like on these massive worlds.
Oceans on Earth are maintained because our planet has water coating its surface that is supplemented by oceans worth of water beneath the planet's crust. During volcanic eruptions, often on the sea floor, some of this subterranean water emerges and supplements what's in the oceans. If it weren't for this process, our oceans would eventually disappear due to plate tectonics, which radically shifts the positions of landmasses and water. (And indeed, our oceans have shrunk quite a bit over the past couple billion years.)
On a super-Earth, the plate tectonic process would be even more awe-inspiring. Oceans would take longer to form, but they could be sustained for enormously long periods.
In a release, the Harvard-Smithsonian Center for Astrophysics explains:
[Schaefer] found that planets two to four times the mass of Earth are even better at establishing and maintaining oceans than our Earth. The oceans of super-Earths would persist for at least 10 billion years (unless boiled away by an evolving red giant star).
Interestingly, the largest planet that was studied, five times the mass of Earth, took a while to get going. Its oceans didn't develop for about a billion years, due to a thicker crust and lithosphere that delayed the start of volcanic outgassing.
"This suggests that if you want to look for life, you should look at older super-Earths," Schaefer says.
Given that scientists expect that water is an ideal place for Earthlike life to begin — well, let's just say that a mega-ocean on a mega-Earth that lasts for billions of years would be a great spot to locate a science fiction novel about first contact. Or, you know, a good place to send a generation ship.
Read more at the Center for Astrophysics