Research sheds light on the destinies of atmospheres in distant planets

In a recent investigation conducted by two scientists from the University of Chicago, the evolution of atmospheres on planets orbiting distant stars was explored. Surprisingly, it was discovered that many of these planets do not possess atmospheres similar to Earth’s, but instead have dense layers of hydrogen. Through the use of simulated planet models, the scientists estimated that it is highly unlikely for a planet with a hydrogen atmosphere to transform into one resembling Earth’s atmosphere. In fact, these planets often end up losing their atmospheres entirely.The findings of this study, which were published on July 21 in the Proceedings of the National Academy of Sciences, enhance our comprehension of the formation and development of planetary atmospheres. Additionally, this research can assist astronomers in identifying the most promising locations to search for planets with Earth-like atmospheres.

Asst. Prof. Edwin Kite, the first author of the study and an expert in the history of Mars and the climates of other worlds, explained, “The habitable zone for planets is like a cosmic shoreline, balancing between having too much or too little atmosphere. The question of whether there are numerous planets situated along this shoreline or if they are rare is a significant inquiry in the field of planetary science.”Megan Barnett, a graduate student and the second author of the paper, highlighted the limited knowledge we currently possess regarding the atmospheres of rocky exoplanets. She stated, “Although the planets we examined in this study are too close to their stars to support life, studying them aids in our understanding of the overall processes involved in the formation or destruction of atmospheres.”

Scientists have discovered that the fate of rocky planets with hydrogen atmospheres after their initial formation remains uncertain. They have conducted simulations using various planet sizes and types of atmospheres to explore different scenarios. For instance, they examined the effects of changes in the brightness of nearby stars, which alter the amount of radiation received by the planet, as well as the cooling of the planet’s rock due to the dimming of the star or volcanic eruptions on the surface.

Based on their findings, it appears that if a planet begins with a hydrogen-rich atmosphere, there are limited circumstances in which it can transition into an Earth-like atmosphere. According to Kite, one of the researchers, this outcome is rare in their model. Instead, the most common result is that the planet loses its atmosphere and remains a barren rock indefinitely.However, there are a few instances where a planet slightly larger than Earth managed to acquire and maintain an Earth-like atmosphere through frequent volcanic eruptions that release gases.

Furthermore, the study revealed that a planet initially possessing an Earth-like atmosphere is more likely to retain it.

According to Kite, the scientists stated that their discoveries will provide valuable insights for the exploration of habitable planets using advanced telescopes like the James Webb Space Telescope, which is set to be launched in the upcoming year. These findings suggest that in order to locate exoplanets with Earth-like atmospheres and warm conditions, it would be beneficial to focus on planets that initially lacked hydrogen atmospheres, revolve around less active stars, or possess exceptional size.

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