system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we discount the possibility of life on extrasolar planets outside their "Goldilocks Zones," when life on moons (Enceladus, Europa) within our own system, well outside our "habitable zone," are possibilities?
gpt
Because we currently have a sample size of 1 planet where we know something we understand to be life exists--so we look for as similar circumstances as we can find.  We know Enceladus and Europa are *possibilities*, but we know life on Earth is a certainty, so we look for other Earths, rather than other Enceladi and Europae.