'Independence Day' explained: How is the alien invasion defeated?

In Independence Day (1996) they filmed Will Smith dragging the alien across the salt flats of Utah. Will Smith improvised the "And what the hell is that smell?" Nobody warned him of the horrible smell that sometimes comes of the Great Salt Lake due to billions of dead brine shrimp each year.

‘Independence Day’ – The 1996 Summer Blockbuster and Its Truly Terrifying Aliens