Scientists have largely thought that planets entirely enveloped in deep ocean would not be friendly to alien life. The idea is that these water worlds could not support the cycling of minerals and gases, the process that stabilizes the climate on Earth.
Keeping The Climate Stable
Study researchers Edwin Kite, from the University of Chicago, and Eric Ford, from Pennsylvania State University, however, found evidence suggesting it is possible that water worlds could be habitable.
It takes an extended period for life to evolve. Scientists hunting for extraterrestrial life often search for planets with both some water and some way to keep climates stable over time.
In the case of Earth, the planet cools itself over long timescales by drawing down the greenhouses gases into minerals. Our home planet then warms itself up by releasing these minerals through volcanic eruptions.
This method, however, does not appear to work on water worlds because deep water covers the rocks and suppresses the volcanoes.
In a new study, which was published in The Astrophysical Journal on Aug. 30, Kite and Ford sought to know if there is another way that water worlds can keep their climate stable. They conducted simulations with thousands of randomly generated planets and looked at how the climates in these worlds evolved over billions of years. The duo found that many of these planets stay stable for more than a billion years.
Lucky Planets
These planets tend to sit in the right location around their host stars. They also have the right amount of carbon and do not have too many minerals and elements from the crust dissolved in the oceans that could pull carbon out of the atmosphere.
These lucky planets also have a sufficient amount of water from the start. They likewise cycle carbon between the ocean and the atmosphere only. Given the right concentrations, this is enough to keep the climate stable in these planets.
"We show that chance variation of initial conditions, with no need for geochemical cycling, can yield multi-Gyr surface habitability on waterworlds," the researchers wrote in their study.
Life Does Not Require An Earth Clone
Kite and Ford said that their findings suggest that life does not necessarily require an Earth clone, one with some land and a shallow ocean, to thrive.
"It does seem there is a way to keep a planet habitable long-term without the geochemical cycling we see on Earth," Kite said.
