Planetary Science and Exploration Seminar, Barron Nguyen / Alexis Hensley

Barron Nguyen
NSF Graduate Research Fellow /  Coterminal M.S. student in Earth and Planetary Sciences, Stanford University

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

 

Abstract:
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 Bio:
Barron Nguyen is an NSF Graduate Research Fellow and coterminal M.S. student in Earth and Planetary Sciences at Stanford University, working with Prof. Laura Schaefer. His research spans rocky planet climate and atmosphere evolution, from magma ocean outgassing and tidal heating to XUV-driven escape, including the cosmic shoreline, water inventory evolution, the rocky to sub-Neptune connection, phase curve thermal mapping, and the search for tidal-Venuses and habitable worlds. In parallel, he works to translate these tools into climate resilience and ocean sustainability through a researcher-practitioner lens.

Suggested Readings: 
Zahnle, K. J., & Catling, D. C. (2017). The Cosmic Shoreline: The Evidence That Escape Determines Which Planets Have Atmospheres, and What This May Mean for Proxima Centauri B. The Astrophysical Journal, 843(2), 122. https://doi.org/10.3847/1538-4357/aa7846
Nguyen, B. K., Schaefer, L. K., Ji, X., Theissen, C. A., Dai, F., Peng, B., Tang, Y., Zorzi, A., Hill, M., & Weiner Mansfield, M. (2026). An Evolving Cosmic Shoreline and Sandbar Bounding the Rocky Airless Valley. The Astrophysical Journal Letters, 1008(1), L4. https://doi.org/10.3847/2041-8213/ae9743

 

Alexis Hensley
PhD Student, Geophysics, Stanford University

Magnetic Susceptibility as a Probe of Lunar Regolith Maturity

Abstract:
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 Bio:
Alexis Hensley is a Geophysics Ph.D.  student under the supervision of Prof. Sonia Tikoo. She received her B.A. in Physics and Geology from Berea College in 2025. During her undergraduate studies her research was primarily concerned with Earth’s radiation belt processes, in particular demonstrating the use of GPS satellite monitoring during radiation belt dropout events. Her recent work primarily investigates lunar magnetic mineralogy and broadly, lunar magnetism coupled with space weathering interactions.

Suggested Reading: Bentley et al. (2009) https://doi.org/10.1016/j.pss.2009.07.013