This story, though, raises the question of why there is but a single ejecta layer of iridium and shocked quartz in late Cretaceous rocks around the world.

ECONOMIST: Mass extinctions

Rocks laid down at the time - some 65.5 million years ago - show a thin layer abundant in rare elements like Iridium, spherules and shocked Quartz that could only have come from a meteorite impact.

BBC: Closing the 'three metre gap'

Further examination revealed a crater rich in shocked quartz and iridium, minerals that are commonly found at impact sites. (These are also the telltales in distant layers of ejecta that the rock in question has come from an impact.) Most important, the rocks above and below Shiva date it to 65m years ago.

ECONOMIST: Mass extinctions