Astronomers have been busy looking for an Earth twin in faraway star systems, but according to a new study, if we are looking for life we shouldn’t exclude water worlds from that search. Exoplanets covered in oceans are still good places for life to evolve.
Ocean world lacks some aspects that have been crucial to life on Earth. Without landmasses, minerals and gases won’t circulate, and the climate would be too wild to allow for life to evolve. As reported in the Astrophysical Journal, this is not exactly the case.
In a series of simulations, planetary scientists looked at thousands of randomly generated potential exoplanets. The team discovered that habitability on the planet depends strongly on ocean chemistry and that many of these water worlds remain stable for a really long time. And long-term climate stability might mean life.
"How much time a planet has is basically dependent on carbon dioxide and how it's partitioned between the ocean, atmosphere, and rocks in its early years," lead author professor Edwin Kite, from the University of Chicago, said in a statement.
"It does seem there is a way to keep a planet habitable long-term without the geochemical cycling we see on Earth. The surprise was that many of them stay stable for more than a billion years, just by luck of the draw. Our best guess is that it's on the order of 10 percent of them."
The study simulated planets around Sun-like stars, but it could be extended to other types of stars like red dwarfs. Red dwarfs are the most common type of stars in the universe and they increase in brightness steadily, potentially giving a bit more time to exoplanets to develop a stable climate. The Trappist-1 system, one of the closest to Earth, has several water worlds the size of our planet in the habitable zone of its ultra-cold red dwarf. Research surrounding it shows that it could be an interesting place to look for life.
"This really pushes back against the idea you need an Earth clone – that is, a planet with some land and a shallow ocean," Kite added.
We are still a few years off for detailed analyses of terrestrial exoplanet atmospheres, but research like this points out how our definition of "habitable" might need a bit expanding when it comes to the universe.