Overview

• The analysis, presented at the EPSC–DPS2025 meeting in Helsinki by Dr. Manuel Scherf and Prof. Helmut Lammer of the Austrian Academy of Sciences, argues that ETIs in our galaxy are probably rare.
• Simulations indicate that a planet with about 10% carbon dioxide could sustain photosynthesis for roughly 4.2 billion years, compared with about 3.1 billion years at 1%.
• The study posits a minimum of around 18% atmospheric oxygen for open‑air fire and metal smelting, framing these as prerequisites for technological pathways.
• Statistical comparisons suggest another technological species would need to last at least about 280,000 years to overlap with humanity in time, with ten overlapping civilizations requiring average lifetimes above about 10 million years.
• The nearest technological civilization could be around 33,000 light‑years away and likely older than ours, with authors emphasizing significant biological and cultural uncertainties and calling for continued SETI searches.