An asteroid 1 km or larger striking Earth would release energy equivalent to millions of nuclear weapons, triggering immediate regional devastation followed by a global impact winter caused by ejecta blocking sunlight. An object 10 km in diameter — comparable to the Chicxulub impactor that ended the Cretaceous period — would trigger a mass extinction event eliminating 75%+ of species.
Unlike science fiction, we would likely have years to decades of warning for any large impactor. The challenge is not just detection but the enormous technical and political challenge of deflection. The Ark is not a planetary defence system — it is the insurance policy for when deflection fails.
NASA's Planetary Defence Coordination Office tracks near-Earth objects larger than 140 metres. As of 2026, there are over 2,000 confirmed Potentially Hazardous Asteroids. The probability of a civilisation-ending impact within any given century is low — but low probability is not zero probability.