In the middle of the large illuminated region is an ocean of molten rock, over which lies an atmosphere of rock vapor. Supersonic winds blow on the cold and airless night side and condense to rock rain and snow that flow lazily back into the hottest region of the Magma Ocean. Photo credit: Julie Roussy, McGill Graphic Design, and Getty Images
‘Rocky’ weather could change the surface and atmosphere over time Exoplanet K2-141b.
Among the most extreme planets discovered beyond the margins of our solar system are lava planets: fiery hot worlds that orbit 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 such exoplanet is even stranger. These are evaporation and precipitation from rocks, supersonic winds with a speed of over 5000 km / h and a 100 km deep magma ocean.
In a study published in Monthly announcements from the Royal Astronomical SocietyScientists use computer simulations to predict conditions on K2-141b, an Earth-sized exoplanet with a surface, ocean, and atmosphere made up of the same components: rocks. The extreme weather predicted by their analysis could permanently alter the surface and atmosphere of K2-141b over time.
“The study is the first to make predictions about weather conditions on K2-141b that can be captured with next-generation telescopes like the one hundreds of light years away James Webb Space TelescopeSays lead author Giang Nguyen, a York University graduate student who worked on the study under the supervision of Professor Nicolas Cowan of McGill University.
Two thirds of the exoplanet are exposed to endless daylight
When analyzing the exoplanet’s lighting pattern, the team found that about two-thirds of K2-141b are exposed to constant daylight – and not the illuminated hemisphere we’re used to on Earth. K2-141b is one of a subset of rocky planets that orbit very close to their star. This proximity holds the exoplanet in place gravitationally, which means that the same side is always facing the star.
The night side has icy temperatures below -200 ° C. The day side of the exoplanet is hot enough, at an estimated 3000 ° C, not only to melt stones but also to evaporate, which ultimately creates a thin atmosphere in some areas. “Our finding likely means that the atmosphere stretches a little beyond the shores of the Magma Ocean, which makes it easier to find with space telescopes,” said Nicolas Cowan, professor in the Department of Earth & Planetary Sciences at McGill University.
Like the earth’s water cycle, only with stones
Remarkably, the rock vapor atmosphere generated by the extreme heat fails. Just as the water cycle on earth, in which water evaporates, rises into the atmosphere, condenses and falls back as rain, so also sodium, silicon monoxide and silicon dioxide on K2-141b. On earth, rain flows back into the oceans, where it evaporates again and the water cycle repeats. On K2-141b, the mineral vapor formed from evaporated rock is washed onto the cold night side by supersonic winds, and stones “rain” back into a magma ocean. The resulting currents flow back to the hot day side of the exoplanet, where the rock evaporates again.
Still, the cycle on K2-141b is not as stable as that on Earth, say the scientists. The reflux of the Magma Ocean to the day side is slow, and as a result, they predict that the mineral composition will change over time – which will ultimately change the surface and atmosphere of K2-141b.
“All the rocky planets, including Earth, started out as molten worlds, but then quickly cooled and solidified. Lava planets give us a rare glimpse into this phase of planetary evolution, ”says Professor Cowan from the Department of Earth and Planetary Sciences.
The next step will be to test whether these predictions are correct, the scientists say. The team now has data from the Spitzer Space Telescope, which should provide an initial insight into the day and night side temperatures of the exoplanet. With the launch of the James Webb Space Telescope in 2021, they can also check that the atmosphere is behaving as predicted.
Reference: “Modeling the atmosphere of the lava planet K2-141b: Effects on low and high resolution spectroscopy” by T. Giang Nguyen, Nicolas Cowan, Agnibha Banerjee and John Moores, November 3, 2020, Monthly announcements from the Royal Astronomical Society.
DOI: 10.1093 / mnras / staa2487
