DIX Planetary Science Seminar

One of the most profound findings from NASA's Kepler mission is the unexpected dearth of close-in exoplanets of sizes 1.5 to 2.0 Earth radii, i.e., a radius valley. This valley divides the population of the most abundant class of planets yet known, those between the sizes of Earth and Neptune, into small planets with Earth-like compositions and large planets with hydrogen-rich atmospheres or ice-rich interiors. Recently, we demonstrated that atmospheric mass-loss driven by the cooling luminosity of a planet and its host star's bolometric luminosity can explain this observation, even in the absence of any other process. In this talk, I will describe the key physical processes that drive this core-powered mass-loss mechanism. I will present how our results compare with observations, the insights they give us and the testable predictions we make as a function of planet and host-star properties. This will include sharing our latest work on the characteristics of the radius valley around M dwarfs.

One of our significant findings is that most observed exoplanets have hydrogen atmospheres interacting with molten or super-critical interiors for millions to billions of years. In our Solar system, we see this for planets such as Jupiter and Neptune. Studies show that such interactions can have far-reaching implications for an atmosphere's composition, structure, and evolution. However, we hardly understand these interactions, and studying them in a laboratory is difficult. I will discuss how we address this problem using quantum mechanical molecular dynamics. Specifically, I will share the findings of our upcoming work on the solubility of a planet's hydrogen atmosphere in its super-critical water interior and their implications for planets and exoplanets such as Neptune.