Venus
Second planet from the Sun; surface conditions (~735 K, ~92 atm CO₂) are uninhabitable for known life, but the cloud deck at ~48–60 km altitude has a temperate temperature/pressure window that has been the focus of repeated biosignature speculation, including the contested 2020 phosphine detection.
Earth-to-Venus panspermia (2026)
Per src-venus-panspermia-earth-origin-2026-04, a jhuapl/sandia-national-laboratories team presented modeling at LPSC 2026 showing that natural panspermia from Earth to Venus is physically plausible. Combining the venus-life-equation with bolide pancake-model fragmentation simulations, the authors estimate ~100 viable Earth-derived cells dispersed in Venus’s clouds per Earth year and ~20 billion over the past 1 Gyr.
This means any future detection of microbial life in Venus’s clouds carries a non-trivial Earth-contamination prior — see false-positive-biosignatures.