What are the motifs in The Martian Chronicles by Ray Bradbury?

Spendor, a member of the fourth expedition, speaks of the greed of man. He points out that greed has caused the commercialization of even the most ancient and priceless historical monuments of Earth. Spendor predicts the same will occur on Mars. He is proven correct, as man's greed eventually destroys the Martian planet as well as the planet Earth. The greed of men such as Parkhill, who kills two Martians, destroys an ancient city, and fires on ancient sand-ships in an effort to hold on to his hot dog stand, clearly show the dire consequences of greed. In the end, Parkhill realizes he has lost everything as war comes to Earth, and thus, the actions against the Martians were unnecessary.