Terraforming means changing the environment of a planet so that it is similar to earth's. on mars, the average temperature is about minus 60 degrees celsius. so one of the main goals of terraforming mars is to warm it up. one idea for warming mars comes from a problem here on earth-climate change. most scientists agree that earth is becoming warmer due to increased levels of greenhouse gases in our atmosphere. we might create similar condition on mars by building factories that release greenhouse gases. the gases will change the atmosphere on mars. rain will fall, and it may be possible to grow plants for food. the plants will add more oxygen to the air.