To truly understand the atmospheres of low-mass rocky exoplanets as they evolve, scientists are diving deep into their nature and composition. This exploration is crucial for interpreting observational data.

During the magma ocean phase of terrestrial and sub-Neptune planets, a fascinating exchange occurs between the planet's interiors and its atmosphere. This interaction is influenced by the planet's volatile materials, the chemical balances at play, and how gases and fluids dissolve in molten rock.

As temperatures drop and the atmosphere cools, changes unfold. Gas-phase reactions and condensation reshape the atmospheric landscape. To investigate these phenomena, a groundbreaking open-source Python package called Atmodeller has been developed using JAX, allowing for sophisticated simulations that mimic the conditions of planets like TRAPPIST-1e and K2-18b.

Atmospheric Evolution: Key Findings for TRAPPIST-1e

For planets similar to TRAPPIST-1e, simulations reveal a striking trend: during the magma ocean stage, CO-rich atmospheres reign. As these planets undergo isochemical cooling, their atmospheres transform predominantly into CO2-rich environments, reaching pressures of several hundred bar at a temperate 280 K. Remarkably, nearly 40% of these simulations indicate the potential coexistence of liquid water, graphite, sulfur, and ammonium chloride—all essential ingredients for potential habitability!

The Sub-Neptune Dilemma: CH4 Riches Await?

In the realm of sub-Neptune gas dwarfs, the story shifts. With pressures soaring to several gigapascals, gas behaviors veer away from ideality, drastically boosting solubilities of atmospheric components. This phenomenon results in lower total atmospheric pressures compared to ideal models, leading to the formation of methane-rich atmospheres when total pressures exceed approximately 3.5 GPa. These conditions arise when the hydrogen-to-carbon ratio is around 100 times that of solar proportions, with oxygen levels moderately reducing.

In contrast, at reduced pressures or higher hydrogen-to-carbon ratios, molecular hydrogen remains the primary atmospheric constituent. Regardless of the planet's characteristics, at elevated temperatures, atmospheric solubility shifts the carbon-to-hydrogen ratio, enriching it beyond its initial states.

The research led by Dan J. Bower and his team opens new doors to understanding the atmospheric dynamics of these intriguing worlds, paving the way for future exploration and possibly, the search for extraterrestrial life.