Astronomers have discovered an exoplanet, L 98-59 d, that may possess an atmosphere characterized by sulfur dioxide and hydrogen sulfide, gases associated with unpleasant odors reminiscent of rotten eggs and burnt matches. This finding, published in The Astrophysical Journal Letters on November 1, suggests the planet could have a molten or volcanic surface.
Located approximately 35 light-years away in the constellation Volans, L 98-59 d is classified as a super Earth, slightly larger and heavier than Earth. Utilizing the James Webb Space Telescope, a collaborative effort between NASA and the European and Canadian space agencies, researchers observed the planet orbiting a red dwarf star.
If confirmed through additional studies, L 98-59 d would become the smallest known exoplanet with an atmosphere. Lead author Agnibha Banerjee noted the stark contrast between this planet's atmosphere and those of rocky planets in our solar system, which typically contain more water vapor and carbon dioxide.
Red dwarf stars, the most prevalent type in the Milky Way, present unique challenges for planetary atmospheres due to their violent stellar radiation. The research team employed transmission spectroscopy to analyze the atmosphere by examining starlight filtered through it, identifying missing light wavelengths to determine molecular composition.
Current data is based on a single observation of the planet's transit across its star, leading to some uncertainty regarding the atmospheric interpretation. Banerjee acknowledged that the team slightly favors the atmosphere hypothesis over potential contamination from stellar spots.
While the exoplanet appears inhospitable for life, its potential volcanic activity raises intriguing possibilities. The researchers speculate that L 98-59 d could share similarities with Jupiter's moon Io, known for its intense volcanic activity influenced by gravitational interactions.
Néstor Espinoza, a co-author, is spearheading a broader study utilizing the Webb telescope to explore rocky exoplanets orbiting red dwarfs, aiming to determine the presence of atmospheres in these distant worlds. Initial findings indicate substantial amounts of hydrogen sulfide in L 98-59 d's atmosphere, suggesting a unique environment.