Chemical conditions on Hycean worlds

Area of Science:

• Astrobiology
• Exoplanetary Science
• Planetary Chemistry

Background:

• Traditional exoplanet research focused on rocky planets.
• Hycean worlds, sub-Neptunes with global oceans and H2-rich atmospheres, are a new class of potentially habitable exoplanets.
• Over a dozen candidate Hycean planets are known to transit nearby M dwarfs, making them prime targets for JWST observations.

Purpose of the Study:

• Investigate the atmospheric molecular composition and bioessential element inventory of a canonical Hycean world.
• Explore the chemical evolution and observable present-day atmospheric conditions.
• Assess the potential for prebiotic chemistry and the delivery of essential elements to the ocean.

Main Methods:

• Photochemical and kinetic modeling of atmospheric conditions.
• Analysis of atmospheric evolution under reduced primordial conditions.
• Modeling of bioessential metal delivery mechanisms to the ocean, considering geological factors.
• Estimation of bioessential metal requirements based on ocean depth and early Earth ocean data.

Main Results:

• Reduced primordial conditions can lead to an early atmosphere rich in organic molecules, serving as feedstock for prebiotic chemistry.
• Bioessential metal requirements for life can be met through plausible impact histories, atmospheric sedimentation, and other steady-state sources.
• Hycean worlds present a promising new paradigm for exoplanet exploration and the search for life.

Conclusions:

• Hycean worlds significantly expand the scope of exoplanet habitability studies.
• Their atmospheric and oceanic chemistry are conducive to the origin and sustenance of life.
• JWST and future observatories can characterize Hycean worlds, advancing the search for extraterrestrial life.