Characterizing the Radiative–Convective Structure of Dense Rocky Planet Atmospheres

Abstract We use a one-dimensional line-by-line radiative–convective model to simulate hot, dense terrestrial-planet atmospheres. We find that strong shortwave absorption by H 2 O and CO 2 inhibits near-surface convection, reducing surface temperatures by up to ∼2000 K compared to fully convective predictions. Pure-CO 2 atmospheres are typically 1000 K cooler than pure H 2 O, with only a few percent of H 2 O required to elevate surface temperatures by hundreds of kelvins for a fixed incident stellar radiation. We also show that minor greenhouse gases such as SO 2 and NH 3 have a limited warming effect when H 2 O is abundant. We find that even for insolation values as high as 12,500 W m −2 (37 × Earth’s) planets with mixed CO 2 –H 2 O envelopes have surface temperatures in the 1200–2000 K range, limiting surface melting. Our results highlight the critical role of shortwave heating on magma ocean planets and the need for improved high-temperature spectroscopy beyond 20,000 cm −1 .