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Among the most extreme planets discovered beyond the borders of our solar system are the lava planets – fiery worlds that revolve so close to their host star that some regions are likely oceans of molten lava. According to scientists at McGill University, York University and the Indian Institute of Science Education, the atmosphere and weather cycle of at least one of these exoplanets are even stranger, with evaporation and precipitation of rocks, supersonic winds that they rage over 5000 km / h. and a 100 km deep magma ocean.
In a study published in Royal Astronomical Society Monthly Notices, scientists use computer simulations to predict conditions on K2-141b, an Earth-sized exoplanet with a surface, ocean and atmosphere all made up of the same ingredients: rocks. The extreme weather predicted by their analysis could permanently change K2-141b’s surface and atmosphere over time.
“The study is the first to make predictions about K2-141b weather conditions that can be detected from hundreds of light years away with next-generation telescopes like the James Webb Space Telescope,” says lead author Giang Nguyen, PhD student at York University, who worked on the study under the supervision of Professor Nicolas Cowan of McGill University.
Two thirds of the exoplanet have to face the endless light of day
By analyzing the exoplanet’s illumination pattern, the team found that around two-thirds of K2-141b are exposed to perpetual daylight, rather than the illuminated hemisphere we’re used to on Earth. K2-141b belongs to a subset of rocky planets that orbit very close to their star. This proximity keeps the exoplanet gravitationally locked in place, which means that the same side always faces the star.
The night side experiences freezing temperatures below -200 C. The day side of the exoplanet, at an estimated temperature of 3000 C, is hot enough not only to melt the rocks, but also to vaporize them, eventually creating a subtle atmosphere in some areas. “Our discovery probably means that the atmosphere extends a little beyond the magma ocean shore, making it easier to spot with space telescopes,” says Nicolas Cowan, professor in the Department of Earth and Planet Sciences. at McGill University.
Like the Earth’s water cycle, only with rocks
Surprisingly, the rock vapor atmosphere created by extreme heat experiences precipitation. Just like the water cycle on Earth, where water evaporates, rises into the atmosphere, condenses, and falls back as rain, so do sodium, silicon monoxide and silicon dioxide on K2-141b. On Earth, the rain flows back into the oceans, where it will evaporate once again and the water cycle will repeat itself. On K2-141b, the mineral vapor formed by the evaporated rock is swept to the frigid side of the night by the supersonic winds and the rocks “rain” again in an ocean of magma. The resulting currents ebb towards the warm side of the exoplanet, where the rock evaporates once again.
However, the cycle on K2-141b is not as stable as on Earth, scientists say. The ocean’s return flow of magma to the day side is slow, and as a result, they predict that the mineral composition will change over time, eventually changing the surface and atmosphere of K2-141b.
“All rocky planets, including Earth, were born as molten worlds, but then quickly cooled and solidified. The lava planets give us a rare glimpse at this stage of planetary evolution,” says Professor Cowan of the Department of Earth and Planet Sciences.
The next step will be to check whether these predictions are correct, say the scientists. The team now has data from the Spitzer Space Telescope that should give them a first glimpse of the exoplanet’s day and night temperatures. With the launch of the James Webb Space Telescope in 2021, they will also be able to see if the atmosphere is behaving as expected.
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