No one’s sure if synthetic mirror life will kill us all. For four days in 2019, scientists hunkered down to brainstorm the impossible—mirror bacteria with proteins twisting in the opposite direction. Excitement turned to alarm by 2024 as researchers feared these organisms could evade our immune systems and spread unchecked.

Despite this, some doubt whether mirror life is even feasible. Molecular biologist Ting Zhu argues that speculation should not guide decision-making, warning against a broad moratorium on early-stage research.

The road to creating mirror-life organisms remains complex and costly. Yet the risks are real enough for a global conversation among chemists, synthetic biologists, bioethicists, and policymakers. The question is: when does science become science fiction?