A shadow biosphere is a hypothetical microbial biosphere of Earth that would use radically different biochemical and molecular processes from that of currently known life. Although life on Earth is relatively well studied, if a shadow biosphere exists, it may still remain unnoticed because the exploration of the microbial world targets primarily the biochemistry of the macro-organisms.

https://en.wikipedia.org/wiki/Shadow_biosphere

For this market, the form of life discovered should be different enough to suggest that it doesn't have a common ancestor with typical life