By fertilizing inorganic regolith with organic human waste that has been processed through bioreactors, future astronauts living on Mars could be able to create their own organic soil.
One feature of the Solar System that doesn't require a complex explanation is the cratered surfaces of some of the planets and moons. These surfaces have been pummeled by impacts, and on some bodies, these impacts are defining features. The craters tell the tale of our Solar System's history.

