Water is the sustenance of primitive life. Scientists have known this well for decades, since sometime about three billion years ago the first life forms formed in Earth’s oceans. In this early age, the Earth was a ball of blue covered almost entirely by water, and only dotted by a few islands of volcanic origin.
Through powerful telescopes that are launched into space, scientists ‘travel’ through the known universe in search of life or worlds where it can sustain itself, select the planets where, in our experience, life is most likely to exist, and discard those worlds where it is less likely, such as very hot gas giants; and they point the objective towards exoplanets similar to the Earth: formed of rock, with liquid water and in the zone of habitability of their star.
Scientists had assumed that planets that are covered by a deep ocean would not be able to provide the cycle of minerals and gases that keeps the climate stable and therefore would not be fit for life.
But a study published in The Astrophysical Journal concludes that oceanic planets can remain at the optimal point of habitability for longer than previously thought.
Those responsible for the study are scientists from the University of Chicago and the State of Pennsylvania, who have discovered, thanks to more than a thousand simulations, that the living conditions that survive on planets totally covered with water are more fluid than what is expected. thought.
The conclusions of this study contradict the idea that a clone of Earth is necessary to support life , that is, a planet with a little land and a shallow ocean.
A stable climate is the key to sustaining life
Because life takes a long period to evolve, and because the amount of light and heat on planets can vary as stars age, scientists generally look for planets that have some water and are able to maintain its stable climates over time. Our planet is cooled by absorbing greenhouse gases from minerals and warmed by releasing them through volcanoes. But this model does not work in an aquatic world, with deep waters that cover the rock and cancel the function of volcanoes, which in theory would prevent the climate from being stable.
To see if there is another way for a planet’s climate to remain stable, the study authors set up a simulation with thousands of randomly generated planets and tracked the evolution of their climates over billions of years. The surprise was that many of them were stable for more than a billion years .
How does an ocean planet keep the climate stable?
These lucky planets are in the ideal zone of their stars: they had the right amount of carbon, and not too many minerals and elements of the crust dissolved in the oceans. What they would do is cycle carbon between the atmosphere and the ocean, which, in the right concentrations, is enough to keep the climate stable.
“The climate that a planet has depends basically on carbon dioxide and how it is divided between the ocean, the atmosphere and the rocks in its early years. But it seems that there is another way to keep a planet habitable in the long term, other than the cycle geochemical that we see on Earth “, detail the researchers.
Researchers believe that planets in red dwarf systems are promising candidates for promoting life because these stars become brighter much more slowly, giving their planets much longer time to warm up to generate life. .
The case of Europe: a frozen world candidate for life
In fact, in the Solar System itself there are some candidates to be carriers of life that do not resemble Earth. One of them is Europa, one of the moons of Jupiter. It is a frozen world, which has several cracks in the thick layers of ice that cover its surface. Scientists soon hope to send a probe to pierce the ice and perhaps discover an ocean rich of life, tempered, thanks to the gravitational force of the gas giant, which would heat the rocky core of Europa.
Reference: ‘Habitability of Exoplanet Waterworlds’. Edwin S. Kite and Eric B. Ford. (2018 August 31). The American Astronomical Society. Doi: 10.3847 / 1538-4357 / aad6e0
Image credit: NASA / JPL-Caltech.
