April 23, 2025

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Speaker: Renyu Hu, Research Scientist, NASA Jet Propulsion Laboratory

Title: Exploring New Frontiers in Planetary Astronomy: From Magma Oceans to Liquid-Water Worlds

Abstract: The discovery of over 5,000 exoplanets has revolutionized our ability to address fundamental questions about planetary habitability and evolution: Are there Earth-like worlds in the Universe? Can they support life? My research accelerates the discovery and characterization of habitable planets by combining cutting-edge observations with advanced models to characterize the atmospheres and surfaces of rocky and low-temperature exoplanets, trace their evolutionary pathways, and search for signs of liquid-water oceans.

In this talk, I will discuss recent breakthroughs in the study of rocky exoplanets, including the first detection of a magma-ocean atmosphere on 55 Cancri e and the discovery of a volcanic, SO₂-rich atmosphere on L 98-59 b using JWST. These findings provide unprecedented insights into the interplay between geological processes and atmospheric evolution, establishing the emerging field of exoplanet geology. I will also present ongoing efforts to identify liquid-water conditions on temperate sub-Neptunes, illustrating how innovative models, such as our next-generation planetary atmosphere framework, EPACRIS, enable us to predict key atmospheric signatures and interpret groundbreaking JWST observations.

Finally, I will discuss the path forward for characterizing Earth-like planets and highlight how today’s exoplanet studies drive scientific and technological priorities of future exploration.

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Biography: Dr. Renyu Hu is an expert in the physical and chemical processes, evolution, radiative transfer, and remote sensing of planetary and exoplanetary atmospheres. Dr. Hu received his Ph.D. in planetary science from the Massachusetts Institute of Technology in 2013, and joined JPL as a research scientist in 2015. Dr. Hu developed, from the first principles, a general-purpose photochemical and thermochemical model for exploring the diversity of exoplanets, which has led to the first classification framework of mini-Neptunes, a search strategy for helium-atmosphere exoplanets, and the prediction of an O2-CO runaway state on M stars’ rocky planets. He also pioneered the method to detect minerals on bare-rock exoplanet surfaces. In addition to exoplanets, Dr. Hu uses stable isotopes to study the evolution of planetary atmospheres. For example, his research has led to evidence for a moderately dense early atmosphere on Mars, probably having a substantial fraction of nitrogen. Through these and many other research projects, Dr. Hu’s research group has played a significant role in both the deep characterization of exoplanets and the debate on the ancient climate of Mars, leading multiple efforts to characterize exoplanets using Hubble, Spitzer, TESS, and JWST. Dr. Hu is supervisor of the Exoplanet Systems group at JPL, and is one of the project scientists and exoplanet theme lead of the Habitable Worlds Observatory, NASA’s flagship mission in development to search for Earth 2.0 and life outside our solar system.