Enhanced flux of extraterrestrial ³ He across the Permian–Triassic boundary

The ca 252 Ma Permian–Triassic boundary (PTB) represents the most severe mass extinction event of the Phanerozoic, with the disappearance of ~ 80% of marine invertebrate species. Large-scale eruption of the Siberian Traps is the commonly favored cause, although the link between volcanism and extinction remains debated. Here, we report evidence for an extraterrestrial ³ He influx in the PTB section of deep-sea bedded cherts from Japan. This unusual signal indicates a significant increase in the influx of interplanetary dust particles, likely related to an asteroid shower in the inner solar system. High-resolution stratigraphy indicates that the peak flux of dust particles occurred during the final 500 kyr of the Permian, concurrent with a pre-extinction decline in radiolarian diversity. [Figure not available: see fulltext.].