Avi Loeb and co-author Shokhruz Kakharov examine whether methane detected in interstellar object 3I/ATLAS could be a biosignature. They analyze both natural panspermia — microbes frozen in an interstellar iceberg revived by solar heating near perihelion — and directed panspermia, where a technological civilization deliberately places life-bearing capsules inside such objects. Using data from SPHEREx and the Webb Space Telescope, they calculate that while frozen survival metabolism would require an implausible quadrillion kilograms of biomass, active methanogenic archaea in warm liquid settings could produce the observed methane with only ~100 tons of biomass. They also explore engineering constraints for directed panspermia, noting that hypervelocity impacts would destroy biological payloads and that gentle emplacement analogous to OSIRIS-REx would be required. The paper concludes that natural panspermia is plausible but requires credible liquid-water activation pathways, while directed panspermia demands careful thermal and mechanical engineering.
