Exoplanets & Habitability Seminar, March 14th, 2023 ath 10:15h

Host
Eleonora Alei

Speaker
Thea Kozakis

Title
Is ozone a reliable proxy for molecular oxygen?

Abstract
Molecular oxygen (O2) paired with a reducing gas is regarded as a promising biosignature pair for atmospheric characterization of terrestrial exoplanets. In circumstances when O2 may not be detectable in a planetary atmosphere (i.e., at mid-IR wavelengths) it has been suggested that O3, the photochemical product of O2, could be used as a proxy to infer the presence of O2. While O3 is not directly produced by life, it plays an important role in habitability as the ozone layer is the primary source of UV shielding for surface life on modern Earth. However, O3 production is known to have a nonlinear dependence on O2, as well as being strongly influenced by the UV spectrum of the host star. To evaluate the reliability of O3 as a proxy for O2 we used Atmos, a 1D coupled climate/photochemistry code, to study the O2-O3 relationship for "Earth-like'' habitable zone planets around a variety of stellar hosts (G0V-M5V) for O2 abundances from 0.01%-150% of the Present Atmospheric Level (PAL) on modern Earth, as well as for varying biological surface fluxes. We found that the O2-O3 relationship differed significantly around different stellar hosts, with different trends for hotter stars (G0V-K2V) than cooler stars (K5V-M5V), with the main factor being the UV spectrum of the host star. In this talk I will discuss the atmosphere chemistry processes driving O3 formation and destruction, as well as how observational signals of O3 would vary in different scenarios.

Time
Tuesday 14th of March, 10.15 to 11am (Zürich time).

Zoom link
Time: 14 mars 2023 10:00 AM
external pagehttps://ethz.zoom.us/j/63326237268call_made