Why This Is Hell

I forgot to crosspost this

( CXXXII: Kate Wilhelm, The Clewiston Test (1976) )

( CXXXIII: Richard Brautigan, The Abortion: An Historical Romance 1966 (1971) )

( CXXXIV: Richard Brautigan, Dreaming of Babylon: A Private Eye Novel 1942 (1977) )

( CXXXV: Italo Calvino, Invisible Cities (1972) )

( CXXXVI: Barry Malzberg, The Day of the Burning (1974) )

( CXXXVII: David Gerrold, Space Skimmer (1972) )

( CXXXVIII: Doris Piserchia, Earthchild (1977) )

( CXXXIX: Ernest Callenbach, Ecotopia (1975) )

( CXL: Robert Silverberg, The Book of Skulls (1972) )

( CXLI: Charles Platt, The City Dwellers (1970) )

( CXLII: Larry Niven and Jerry Pournelle, The Mote in God's Eye (1974) )

( CXLIII: Larry Niven and Jerry Pournelle, Lucifer's Hammer (1977) )

Okay, so there seem to be a whole number of 1970s sf narratives about asteroids/comets/meteors hitting or nearly hitting the Earth (Rama, Lucifer's Hammer, In the Ocean of the Night, The Hermes Whatsit, Meteor, among others). Why then? The dinosaurs wiped out by asteroid theory (Alverez et al) appears to be 1980, and there's already tracking agencies by the mid-1960s. But what triggered all these stories (albeit not the first, but a rash of them)? Was it a meteor visible above the US in August 1972? Tunguska publicity?

( CXLIV: Thomas Pynchon, Gravity's Rainbow (1973) )