Oral title: Detecting Biosignatures and Pre-Biosignatures in the Atmospheres of Earth-like Planets Around Other 

Oral abstract: When we observe the first terrestrial exoplanet atmospheres, we expect to find planets at a wide range of 
geological conditions and evolution. In our own Solar System we already have three very different terrestrial exoplanets in 
Earth, Mars, and Venus. Additionally the atmospheres of these planets have not been fixed in time. Earth itself offers 
many possible atmospheric states of a planet. We set out to examine how an Earth-like planet at different geological 
epochs might look around other star types (F, G, K and M dwarf stars). Additionally, we examine the plausibility of 
detecting prebiotically interesting molecules, such as HCN, NH3, CH4, and C2H6 in an early-Earth type atmosphere. We 
find that some of these molecules could be produced abiotically in a CO2/CH4/H2 rich atmosphere with lighting and 
photochemistry. These molecules would be interesting to detect in an exoplanet atmosphere since they are known to be 
useful for key prebiotic chemical pathways. HCN, for example, is present at each of the initial photochemical reactions 
that produce lipids, amino acids and nucleosides, the three building blocks of life (Patel et al. 2015).  We also look at the 
rise of oxygen and the detectability of combinations of biosignature gases throughout Earth history, modeling the great 
oxygenation event and Neoproterozoic oxygenation event event around other star types. We show the VIS - IR spectral 
features, with a focus on biosignatures observable through geological time for FGKM stars and the effect of clouds on the 
signal.