Distinguishing Oceans of Water from Magma on Mini-Neptune K2-18b

Journal article

Mildly irradiated mini-Neptunes have densities potentially consistent with them hosting substantial liquid-water oceans ("Hycean" planets). The presence of CO2 and simultaneous absence of ammonia (NH3) in their atmospheres has been proposed as a fingerprint of such worlds. JWST observations of K2-18b, the archetypal Hycean, have found the presence of CO2 and the depletion of NH3 to 4 μm region, where CO2 and CO features dominate: magma ocean models suggest a systematically lower CO2/CO ratio than estimated from free-chemistry retrieval, indicating that deeper observations of this spectral region may be able to distinguish between oceans of liquid water and magma on mini-Neptunes

Authors: Shorttle, O; Jordan, S; Nicholls, H; Lichtenberg, T; Bower, DJ

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Astronomical Society
• Journal: The Astrophysical Journal Letters
• Volume: 962
• Issue: 1
• Pages: L8-L8
• Publication date: 2024-02-02
• DOI: 10.3847/2041-8213/ad206e
• EISSN: 2041-8213
• ISSN: 2041-8205
• Language: English
• Keywords: Astrophysics; Astrobiology; Environmental science; Water vapor; Magma; Volcano; Geology; Geochemistry; Physics; Meteorology; Planet