THE PLANET IN WHICH EVEN THE SKY IS OF ROCK
At the center of the large illuminated region is an ocean of molten rock covered by an atmosphere of rock vapor
This extrasolar world has a magma ocean 100 km deep.
The lava planets are some of the most extreme discovered beyond the limits of the solar system. These are fiery worlds that spin so close to their star that some regions are probably oceans of molten lava.
An international team studied a particularly strange one, in which rocks evaporate and rain, supersonic winds blow at more than 5,000 km per hour and there is a magma ocean 100 km deep. It is located 202 light-years from Earth. Could there be anything more like hell?
Scientists have run computer simulations to predict atmospheric and meteorological conditions for this Earth-size world, called K2–141b and discovered in 2018, in which the surface, ocean, and atmosphere are made up of the same ingredients: rocks. . Over time, they conclude in the journal “Monthly Notices of the Royal Astronomical Society,” the extreme weather predicted by their analysis could permanently change the exoplanet’s surface and atmosphere.
“The study is the first to make predictions about weather conditions on K2–141b that can be detected from hundreds of light-years away with next-generation telescopes such as the James Webb spacecraft,” says lead author Giang Nguyen of the University of York.
Exoplanet’s illumination pattern
By analyzing the exoplanet’s illumination pattern, the team found that roughly two-thirds of K2–141b face perpetual daylight, rather than the illuminated hemisphere we are used to on Earth. K2–141b belongs to a subset of rocky planets that orbit very close to its star. It takes just 0.28 days to complete one orbit, just 6.7 hours. This proximity keeps the exoplanet gravitationally locked in place, meaning that the same side always faces the star.
The night side experiences cold temperatures below -200 ° C, while the daytime, at 3,000 ° C, is hot enough not only to melt rocks but also to vaporize them, eventually creating a thin atmosphere in some areas. “Our finding probably means that the atmosphere extends a bit beyond the shoreline of the magma ocean, making it easier to locate with space telescopes,” says Nicolas Cowan, a professor in the Department of Earth and Planetary Sciences at McGill University.
Like the water cycle
Surprisingly, the rock vapor atmosphere created by extreme heat causes precipitation. Much like the water cycle on Earth, where water evaporates, rises into the atmosphere, condenses, and falls as rain, so does sodium, silicon monoxide, and silicon dioxide in K2–141b. On Earth, the rain returns to the oceans, where it will evaporate once more and the water cycle will repeat. At K2–141b, the mineral vapor formed by the evaporated rock is blown towards the cold side of the night by supersonic winds, and the rocks “rain” back into an ocean of magma. The resulting streams flow back to the hot day side of the exoplanet, where the rock evaporates once more.
Still, the cycle in K2–141b is not as stable as Earth’s, scientists say. The return flow of the magma ocean to the diurnal side is slow and as a result, they predict that the mineral composition will change over time, eventually changing the same surface and atmosphere of K2–141b.
‘All rocky planets, including Earth, started out as molten worlds but then quickly cooled and solidified. The lava planets give us a rare glimpse into this stage of planetary evolution, ”says Cowan.
The next step will be to test whether these predictions are correct, something that scientists will do with data from the Spitzer Space Telescope. The James Webb, which will be released in 2021, will be able to confirm if they are correct.
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