Speaker
Description
L98-59 is an M-dwarf star located about 34.6 light-years away from Earth in the constellation Volans. L98-59 d is an extreme super-Earth exoplanet initially discovered by NASA's TESS in 2019. The JWST and ground-based facilities confirmed it belongs to an entirely new class of molten, sulphur-rich planets.
Volcanism is a critical planetary process that sheds light on internal structure, thermal evolution, volatile cycling, and geodynamics across diverse worlds. While Solar System bodies Venus and Io show volcanic activity driven by internal planetary heat and tidal heating, respectively, the exoplanet L98-59 d offers an important third case for comparative geodynamics beyond our Solar System. On L98-59 d, volcanism does not operate as localised surface eruptions like those seen on Io or Venus. Instead, volcanism manifests as planet-scale magmatism, driven by a deep, persistent, global ocean of molten rock.
This study examines the connections among internal heating, magmatic mechanisms, volatile transport, and atmospheric chemistry by comparing Venus and Io with the inferred properties of L98-59 d, which shows evidence of sulphur-bearing atmospheric species (such as H2S and SO2). Coupled atmosphere-interior models indicate that L98-59 d maintains a persistent magma ocean sustained over billions of years through a combination of tidal heating, strong atmospheric blanketing, and stellar irradiation.
Unlike Venus (mantle convection and stagnant-lid dynamics) or Io (extreme tidal heating from Jupiter), L98-59 d occupies a unique middle ground where a volatile-rich magma ocean acts as an interior storage reservoir that continually outgases sulphur species into its atmosphere. By demonstrating how atmospheric spectroscopy can serve as an indirect probe of interior melting and degassing processes, this comparative approach highlights how principles derived from Solar System analogues can be extended to evaluate the geodynamic diversity and evolution of exoplanetary worlds.