SMuK 2021 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

SYEP: Symposium What makes an exoplanet habitable

SYEP 1: What makes an exoplanet habitable

SYEP 1.2: Hauptvortrag

Mittwoch, 1. September 2021, 14:30–15:00, Audimax

Geological drivers of habitability — •Raymond T. Pierrehumbert — University of Oxford

Atmospheres of rocky planets are dynamic entities, and their evolution is governed by the balance between outgassing from the planetary interior, crustal sinks of atmospheric or oceanic volatiles, and escape of volatiles to space. It is increasingly recognized that geological processes (and not just a planet's position in the nominal habitable zone) are crucial to determining habitability. The role of the deep carbon cycle in determining whether planets near the outer edge of the nominal habitable zone can maintain enough atmospheric CO2 to attain the maximum-greenhouse limit is particularly stark, but there are also issues regarding the circumstances in which the silicate weathering thermostat can prevent CO2 from building up to levels that render the planet uninhabitable. Geological processes also govern other aspects of atmospheric composition having a bearing on emergence of life (as we know it), and of interpretation of biosignatures. These include methane abundance and nitrogen cycling.

In this talk, I will review some of the key processes involved in geological drivers of habitability, including supply of uranium and thorium, representation of continental and seafloor weathering, composition of volcanic outgassing, and the role of magma oceans. Some remarks on special features of hydrogen-dominated atmospheres will be offered. A number of critical unresolved issues will be highlighted.