Scientists Rehearse for a Second Tunguska, Though the Rock Has Not Yet Been Named

MOFFETT FIELD, CALIF. — Experts in the business of imagining the sky falling are preparing a new drill. According to a report by The Debrief, an exercise now under way for the 2027 Planetary Defense Conference is built around a hypothetical impact threat from a roughly Tunguska-sized object.

The account comes from Lorien Wheeler, Impact Risk Assessment lead for NASA's Asteroid Threat Assessment Project at the Ames Research Center. She told the publication that NASA's Center for Near-Earth Object Studies regularly takes part in such exercises to test its assessment methods.

The difficulty, Wheeler says, is how little is known in advance. Asteroids range from weak, loosely bound rubble piles to strong, dense iron-type bodies, and she said that combining these structural uncertainties with uncertainty about size produces a huge range in potential mass and energy.

Her team uses the Probabilistic Asteroid Impact Risk model, which, according to the report, weighs millions of hypothetical impact scenarios to estimate the range and likelihood of damage. Such work supports NASA's Planetary Defense Coordination Office.

Even with the Tunguska event on record, Wheeler said, it is hard to predict how quickly an asteroid might break up, how high it might burst, and how its energy would divide among blast waves, heat, cratering or tsunami waves. The Debrief reports that the simulations are nonetheless improving scientists' ability to evaluate threats and inform defense plans, though not to predict every consequence with certainty.