Overview
- JWST observations in 2024, followed by ground-based data, detected sulfur-bearing gases including sulfur dioxide and hydrogen sulfide in L 98-59 d’s atmosphere.
- Interior–atmosphere simulations reconstructing nearly five billion years indicate a global molten silicate mantle with a magma ocean thousands of kilometers deep, comprising roughly 70–90% of the planet’s interior radius.
- L 98-59 d is about 1.6 times Earth’s radius, resides roughly 34–35 light-years away around a red dwarf, and has a bulk density near 40% of Earth’s, helping explain its unusual atmospheric chemistry.
- The planet’s atmosphere is hydrogen-rich with a very high sulfur content, including an estimated ~10% hydrogen sulfide, and ultraviolet-driven chemistry produces sulfur dioxide while a runaway greenhouse keeps surface temperatures above ~1,500°C.
- The study, published in Nature Astronomy, challenges current small-planet categories and proposes a possible broader class of sulfur-dominated magma-ocean worlds, a hypothesis the team plans to test with further JWST results and upcoming ESA Ariel and PLATO missions using machine-learning analyses.