Historic First Direct Surface Analysis
The James Webb Space Telescope performed the first direct analysis of an exoplanet's surface, marking a major shift from previous studies that focused on atmospheres. Using the Mid-Infrared Instrument (MIRI), astronomers observed thermal infrared light emitted from LHS 3844 b's intensely hot dayside during secondary eclipses in 2023 and 2024. This breakthrough technique allowed scientists to study the planet's geology directly.
Surface Composition and What It Rules Out
Analysis of the infrared spectrum reveals a dark, low-silica surface dominated by basalt and olivine-rich materials similar to Mercury or the Moon. The data ruled out an Earth-like crust rich in silica and granite, which typically form through water-driven geological processes and plate tectonics. No trace concentrations of volcanic gases like carbon dioxide or sulfur dioxide were detected, despite MIRI's ability to sense such compounds.
Two Possible Geological Scenarios
Researchers propose two explanations for the planet's dark, featureless surface. One scenario suggests a relatively young surface shaped by recent volcanic activity, though the absence of detected volcanic gases argues against this. The alternative explanation favors an old, space-weathered surface covered in a thick layer of dark, fine-grained material formed over long periods by radiation and meteorite impacts. Without an atmosphere for protection, the airless world remains especially vulnerable to this space weathering process.
Planet Characteristics
LHS 3844 b orbits a cool red dwarf star every 11 hours, orbiting just three stellar diameters above its host star's surface. The planet is tidally locked, meaning one hemisphere constantly faces the star while the other remains in perpetual darkness. Located 48.5 light-years from Earth, this super-Earth lacks any atmospheric protection from cosmic radiation.
Future Research
Follow-up JWST observations are planned to further refine understanding of the planet's surface properties and determine whether it consists of solid rock or loose, weathered material. Scientists are confident the same mid-infrared spectroscopy technique will clarify the nature of LHS 3844 b's crust and enable study of other rocky exoplanets in the future. 
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