Can someone explain the physics behind manna from heaven?

I remember reading an essay from Isaac Asimov, taking the piss out of a book that explained biblical nonsense as the planet Venus flying by the earth at that time and the hydrocarbons in its tail falling as carbohydrates.

Not much of a chemist but even I had a laugh at the idea of two very different compounds that share elements being... Hang on. He wanted us to believe Venus wandered er.

The book was called " When worlds collide " and a quick google shows that some Christian Science bookshops still sell it.