There was a theorist who theorized a continuous mini-comet bombardment of earth.
I think it was the 1980's when a certain
theorist [his name escapes me] predicted that earth's atmosphere is constantly being bombarded my mini-comets.
His theory fell into disrepute thanks to spacecraft and spaceprobes
observing earth.
But he wasn't the first to link earth's water-supply with (a) comet impact(s).
I think it was the 17th century scientist Robert Boyle who speculated that the Great Biblical Flood was caused by a comet striking earth.