Geothermal environments, in particular their chemistry and microbiology, are of broad scientific interest with respect to the formation of mineral deposits (e.g. Jones et al. 1997) and the ecology of extremophiles, a key component of origin of life studies and astrobiology (e.g. Stetter, 1996). Lipid biomarkers, in comparison to DNA and RNA, are relatively well preserved in geothermal sinters and it is likely that such compounds. once encased in the silica matrix, could persist for extended periods of time (Pancost et al., 2005). Consequently, they can be used to gain insight into microbial diversity and, where preserved in ancient materials, assess past changes in environmental conditions.