NASA video says this is how Mars might once have looked

Scientists, studying data from unmanned missions to Mars, believe the planet had a thick atmosphere and even oceans several billion years ago. Now NASA is letting you see what a young Mars might have looked like.

The video was made to promote the upcoming launch of NASA's next Mars craft, MAVEN, scheduled for lift off from Cape Canaveral on Monday. MAVEN will be studying Mars’ atmosphere for clues to the planet’s past climate.