2023-08-13 04:00:07
Vaporized, the Earth’s oceans would form an atmosphere 270 times more massive than our current atmosphere, while they constitute only 0.02% of the mass of our planet.
Earth subjected to an increased insolation of 10% and implications for the interior and the surface with the old model, assuming a convective atmospheric structure, and with a more coherent model, including the transport of heat by radiation (Radiation, synonymous with radiation in physics, refers to the process of emission or…).
After the formation of the Earth, this reservoir of water was in the form of vapor and it condensed into an ocean once the planet (A planet is a celestial body orbiting around the Sun or another star of…) cooled. The increase in solar luminosity (In astrophysics, solar luminosity is the unit of luminosity…) should vaporize the oceans once more in less than a billion (One billion (1,000,000,000) is the natural integer which follows nine hundred …) years. On Venus, the higher insolation prevented condensation (Condensation is the name given to the physical phenomenon of change of state of matter which…) in an ocean and the atmosphere (The word atmosphere can have several meanings 🙂 of vapor has persisted, giving way to an atmosphere of carbon dioxide (Carbon dioxide, commonly known as carbon dioxide or carbon dioxide, is a…) following its slow erosion by solar UV radiation and the exhaust of hydrogen (Hydrogen is a chemical element with symbol H and atomic number 1.) in space.
These vaporous atmospheres thus play a key role in the history of Earth-like planets and it was believed until now that their greenhouse effect invariably caused the rocky crust to melt into an ocean of magma.
A research team, including CNRS-INSU scientists, have developed a new model to describe these atmospheres more coherently. These simulations show very different properties from previous models which assumed a convective structure and neglected heat transport by radiation. These atmospheres turn out to be cooler and are not necessarily accompanied by magmatic oceans. They are also more sensitive to the type of the host star and the geothermal flux.
The evolution of Venus must therefore be rethought. The magma ocean phase there would have been 100 times shorter than in the standard scenario, limiting the exchanges between the mantle and the atmosphere and preserving the internal water reservoir from escape into space.
The consequences are major for the planets of small red stars, targets of the James Webb space telescope. Magma oceans must be rare there and the relationship between radius, mass and water content needs to be revised, as well as the spectral signatures of such atmospheres.
Reference
A cool runaway greenhouse without surface magma ocean.
Selsis, F., Leconte, J., Turbet, M. et al.
Nature 620, 287-291 (2023).
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