ABSTRACT
In the quest for life in the Universe, the most likely scenario is that we will one day find signs of life, or biosignatures – indications of the occurrence, past or present, of biochemical processes that could have their origin in extraterrestrial biological activity. Interpreters (astrobiologists) will then need to make connections between the expression (the biosignature) and the content (the living organism). The problem with biosignatures is semiotic and epistemological: how can meaning be discovered, deciphered, interpreted, or even invented, starting from material markers. One general epistemological problem of biosignatures is how to recognize the signatures as meaningful: individuate them as expressions that refer to content (i.e., life). A further problem is how to establish the connection between the expression and the content – the biosignature and the biological process that we call life – while ruling out, with a certain degree of certainty, explanations for the signatures that are not of biological nature. This chapter focuses on two major issues in astrobiology: (1) the differentiation of fossils from pseudofossils; and (2) the differentiation of biotic from abiotic processes.
