It's a simple story: war has wrought a nuclearwinter that threatens to wipe out all life on Earth, and the spaceship is sent in search of a "cosmo cleaner" to save humanity.
Since no dinosaur fossils have ever been found in sediments dating from after this point, conventional wisdom has it that the largest creatures ever to roam the earth must have been cut down in their prime - victims of an asteroid impact that sparked firestorms, acid rain and a nuclearwinter that blotted out the sun.
And the nuclear-winter hypothesis (that the smoke from fires caused by a global nuclear war would blot out the sun's rays and thus cool the earth catastrophically) owes its origin, at least in part, to observations of a planet-wide dust storm on Mars.