Sample size/response relationship as a means of discriminating biotic and abiotic signatures

摘要

Attempts to detect extraterrestrial life in-situ are complicated by the possibility of local geochemistry posing as biochemistry. A means is presented to discriminate biotic and abiotic signatures by the time resolved response of progressively smaller sample sizes when added to growth media. A purely geochemical response should show a linear reduction in response as the sample size decreases, however, the effects of saturation must be considered. A biochemical response should show a characteristic growth curve whose onset is progressively delayed with smaller sample sizes. Significantly, the overall shape of the growth curve would remain invariant. Potential complications include variations in growth dynamics such as short lifetimes and/or high mortality rates. A third case is also considered where both geochemical and biochemical responses are present. Experimental results are presented using an electrochemical approach.