Department of Physics & Astronomy
University of New Mexico

Physics and Astronomy Colloquium

A Critical Dependence On Size For Planet Habitability: The Effect Of Nebular Ingassing

Presented by Dr. Zachary D. Sharp, Center for Stable Isotopes (CSI), UNM

Although dozens of approximately Earth-sized planets have been found beyond the Solar System, their suitability as stable habitats for life remains largely unknown. The presence of abundant water in these bodies is a critical factor, however, the processes that deliver water to terrestrial planets orbiting inside the snow line remain contentious, even within the Solar System. Here we use a coupled nebular atmosphere-magma ocean model to demonstrate that direct ingassing to a magma ocean from an early atmosphere derived from the solar nebula readily supplies the vast majority of Earth’s water. The same atmosphere supplies primordial helium in amounts that vastly exceed what is inferred from the compositions of hotspot basalts today. We show that the abundance of ingassed volatiles depends critically on the lifetime of the solar nebula relative to the planet accretion time, and is also a strong function of the planet mass. Terrestrial planets that accrete approximately 40% of Earth’s mass or larger within their stellar nebula ingas multiple oceans of water, whereas Mars-sized (~0.1 Earth mass) bodies ingas little or no water from the same nebula. Earth-sized planets are therefore predicted to be far more volatile-rich than smaller terrestrial planets, and consequently are more promising targets in the search for advanced life.

3:30 pm, Friday, January 18, 2019
Room 125, Dane Smith Hall
Southwest corner of Las Lomas and Yale, Albuquerque, New Mexico

Refreshments will be available before the colloquium, at 3:15 pm, in the lobby of Dane Smith Hall.

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