Scientists Confirm Exoplanet L 98-59 d Features a Global Magma Ocean and Sulfur-Rich Atmosphere

In March 2026, an international consortium of scientists, utilizing data from the James Webb Space Telescope (JWST) and various ground-based observatories, officially confirmed the extraordinary characteristics of the exoplanet L 98-59 d. This distant world is situated approximately 34 to 35 light-years from Earth, orbiting in close proximity to a dim red dwarf star. Due to the intense radiation emitted by its host star, the planet maintains a blistering surface temperature exceeding 1,500 °C, which facilitates the existence of a permanent, global ocean of molten magma across its surface.

Recent findings published in the prestigious journal Nature Astronomy have revealed that the planet's atmosphere is heavily laden with sulfur-based compounds, specifically hydrogen sulfide (H₂S). The primary study, led by Harrison Nicholls of the University of Cambridge’s Institute of Astronomy, highlights the unusually low density of L 98-59 d, even though its physical size is roughly 1.6 times that of Earth. This specific density challenges existing planetary classification frameworks, as the data indicates an absence of the distinct separation between the crust and mantle that is characteristic of terrestrial bodies like Earth.

Advanced modeling of the planet’s evolutionary history over the last five billion years suggests that its interior is composed of a continuous, deep mass of molten material—a global magma ocean that extends thousands of kilometers toward the core. This significant discovery allows for the identification of a new class of planets where heavy sulfur compounds serve as the primary constituent. The research was a collaborative effort involving several experts, including Richard D. Chatterjee from the University of Leeds and Raymond T. Pierrehumbert.

The high concentration of hydrogen sulfide in the atmosphere is considered a direct result of the interaction between the sulfur reservoirs in the planet's interior and a gaseous envelope maintained by a runaway greenhouse effect. Richard D. Chatterjee pointed out that hydrogen sulfide likely plays a fundamental role in the planet's complex atmospheric dynamics. Furthermore, researchers from the University of Oxford who participated in the data analysis suggest that L 98-59 d might have originally been a larger "mini-Neptune" that gradually lost its primary atmospheric envelope over time.

The vast magma ocean serves as a long-term storage site, accumulating significant quantities of sulfur over billions of years, which aligns with observations of other exoplanets subjected to extreme stellar radiation. This molten reservoir likely played a crucial role in helping the planet retain a thick atmosphere despite the intense X-ray radiation from its parent star. Studying extreme environments like L 98-59 d provides scientists with a unique opportunity to investigate the early, molten stages of planetary formation. Future astronomical missions, such as Ariel and PLATO, intend to use these findings to create a more comprehensive map of planetary diversity across the galaxy.