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In recent decades, astronomers have discovered many planets that they believe resemble the Earth, which means they seem terrestrial (ie, Rocky Mountains) and orbit at the right distance. . Unfortunately, recent research has shown that many of these planets may actually be "water worlds," where water is an important part of the mass of the planet.
For the scientific community, this seemed to indicate that these worlds could not remain habitable for a very long time, as they could not support the cycle of minerals and gases that keep the climate stable on Earth. However, according to a new study by a team of researchers from the University of Chicago and the University of Pennsylvania, these "water worlds" may be more livable than we think.
Their study, entitled "Habitability of the exoplanet aquatic worlds", was recently published in The astrophysical journal. The study was conducted by Edwin S. Kite, Assistant Professor, Department of Geophysical Sciences, University of Chicago; and Eric B. Ford, Professor at the University of Pennsylvania's Center for Exoplanets and Habitable Worlds, Institute for CyberScience, and the State Astronomical Research Center of Pennsylvania.
Artistic representation of an aquatic world. A new study suggests that the Earth is in the minority with respect to the planets and that most habitable planets can be greater than 90% of the ocean. Credit: David A. Aguilar (CfA)
For their study, Kite and Ford built models for rocky planets that had several times the water of the Earth, taking into account the evolution of temperature and ocean chemistry over a period of several billion. The purpose of this was to answer some long-standing assumptions about global habitability. The first of these is that the planets must have conditions similar to those of the Earth in order to sustain life over long periods.
For example, planet Earth has been able to maintain stable temperatures over long periods of time by sucking greenhouse gases into minerals (leading to global cooling) and warming up by releasing greenhouse gases via volcanoes. Such a process would not be possible on the aquatic worlds, where the entire surface (and even a significant mass fraction) of the planet is water.
On these worlds, water would prevent the absorption of carbon dioxide by the rocks and suppress volcanic activity. To answer this, Kite and Ford have put together a simulation with thousands of randomly generated planets and have tracked the evolution of their climates over time. They discovered that aquatic worlds would be able to maintain thermal equilibrium for billions of years. As Kite explained in a recent UChicago News press release:
"It really upsets the idea that you need a terrestrial clone, that is, a planet with an ocean and a shallow ocean … The surprise is that many of them remain stable for more than a year. a billion years. Our best guess is that it is in the order of 10% of them. "
The artist's impression of how an Earth-like exoplanet might look like. Credit: ESO
For those planets, which are just at the right distance from their stars, the simulations indicated that there was the right amount of carbon present. And although they do not have enough minerals and dissolved crust elements in the oceans to extract carbon from the atmosphere, they have enough water to circulate carbon between the atmosphere and the ocean. ocean. This process was apparently sufficient to keep the climate stable for several billion years.
"How long does a planet have essentially depends on carbon dioxide and its distribution between the ocean, the atmosphere and the rocks in its early years," said Kite. "There seems to be a way to maintain a livable planet in the long run without the geochemical cycle we see on Earth."
The simulations were based on planets in orbit of stars like our own stars – type G (yellow dwarf) – but the results were also optimistic for the M type stars (red dwarfs). In recent years, astronomers have determined that these systems are promising for life because of their natural longevity and how they fade more slowly over time – which gives much more time to life.
While red dwarfs are also known to be variable and unstable relative to our Sun, resulting in many eruptions that could strip the atmosphere of a planet, the fact that an oceanic world is able to circulate enough carbon for keeping the atmosphere at a stable temperature is encouraging. Assuming that some of the planets orbiting the red dwarfs possess a protective magnetosphere, they may also be able to withstand living conditions for long periods of time.
Proxima b artist impression, discovered using the radial velocity method. Credit: ESO / M. Kornmesser
In recent years, the series of discoveries on exoplanets has led to focus exoplanet studies from detection to characterization. This has led scientists to start speculating on the types of conditions in which life could emerge and thrive. Although the "at your fingertips" approach remains the primary means used by scientists to find potentially habitable planets – where scientists are looking for planets with conditions similar to those of the Earth – it is clear that other possibilities exist.
In the coming years, with the deployment of space telescopes such as the James Webb Space Telescope (JWST) and ground-based telescopes such as the Thirty Meter telescope, the Extremely Large telescope and the giant Magellan telescope, astronomers will be able to characterize the atmospheres of exoplanets and determine whether they are aquatic worlds or planets. continental crust (like the Earth). ).
These same telescopes will also allow astronomers to search for biosignatures in these atmospheres, which will not only help determine if they are "potentially habitable" but "potentially inhabited".
Further reading: UChicago News
By Matt Williams –
Matt Williams is the curator of the Space Guide universe today. He is also an independent writer, science fiction writer and Taekwon-Do instructor. He lives with his family on Vancouver Island, British Columbia.
carbon cycle, earth-like planets, exoplanet atmospheres, exoplanets, featured, life on other planets, aquatic worlds
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