Biosignature False Positives

In our search for life - whether within the earliest part of Earth's geologic record, on planets within our solar system such Mars, or especially for extrasolar planets - we must infer the presence of life from its impact on the local or global environment. These "biosignatures," often identified from the known influence of terrestrial organisms on the Earth's atmosphere and surface, could be misdiagnosed when we apply them to alien worlds. The so-called false positives may occur when another process or suite of processes masks or mimics a biosignature. Here, we examine several leading biosignatures, then introduce potential false positives for these signals, and finally discuss methods to discriminate between the two using current and future detection technologies. We conclude that it is the astrobiology community's responsibility to thoroughly exhaust all possibilities before we resort to "life" as an explanation.