Planetary Science and Exploration Seminar - Two Talks

Recent JWST Insights into Rocky Planet Atmospheres from Habitable to Lava Worlds

The James Webb Space Telescope (JWST) has revealed rocky exoplanets far stranger than Earth and its Solar System siblings. The past three years have brought evidence for thick volatile atmospheres on the hottest lava worlds and bare surfaces on many of the coolest planets. I will briefly review how coupled interior-atmosphere mechanisms, from magma ocean outgassing to XUV-driven escape, shape rocky planet atmospheres in light of these observations. I will revisit the classical “cosmic shoreline,” anchored by Earth, Venus, and Mars, and share our recent findings recasting it as two boundaries set by distinct physics: an outgassing-regulated “cosmic sandbar” and an escape-regulated “cosmic shoreline” bounding an airless valley. Motivating detections include atmospheres on lava worlds 55 Cnc e and TOI-561 b, tentative helium on a temperate rocky M-dwarf world, and possible volcanic sulfur in the exo-Io L 98-59 system. I will close with recent advances and our work bridging planetary science with rocky exoplanet theory and observation, from phase curve mapping and the imprints of formation and migration, to the sub-Neptune connection through the radius valley and desert, and the growing capabilities of exogeology and exoclimatology. Traditional fields such as atmospheric science, paleoclimate, geology, and deep-interior geophysics are beginning to shape how we interpret rocky exoplanets, while exoplanet demographics return the favor by placing Earth and its siblings in a wider context. As JWST and NASA’s next-generation observatories, including the Nancy Grace Roman Space Telescope and Habitable Worlds Observatory, expand this census, we will learn whether Earth and its neighbors, from Venus and Mars to Europa, Titan, and Io, are the exception or the rule.

Speaker: Barron Nguyen, Stanford University

Magnetic Susceptibility as a Probe of Lunar Regolith Maturity

Space weathering refers to the physical and compositional alteration of planetary regolith that is consistently exposed to the harsh space environment. This process produces nanophase metallic iron, thereby increasing the magnetic mineral abundance and the overall bulk magnetic susceptibility compared to non-space-weathered material. On the Moon, with increasing amounts of space weathering, the regolith also becomes enriched in valuable volatiles (e.g., helium-3). Regolith maturity is a relative term corresponding to the amount of space weathering products a surface soil has accumulated. Here, we examine the potential for magnetic susceptibility measurements to provide rapid in-situ estimates of lunar regolith maturity as a simplified alternative to conventional ferromagnetic resonance spectroscopy measurements and discuss implications for in situ resource utilization such as helium-3 prospecting.

Speaker: Alexis Hensley, Stanford University

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Room 350/372