Scientists working on the next Mars Rover mission must choose from a tantalizing array of potential landing sites. There are constraints — enough sunlight to power solar cells, a dearth of sharp boulders — but still, there’s an entire planet to explore. Although Mars is smaller than Earth, with 75 percent of our planet’s surface cloaked in water nearly equal amounts of land are exposed on both. Two Rovers will roam the Red Planet during the 2003 Mars Exploration Rover Mission. The selection process for their landing sites is like a beauty pageant, with scientists nationwide competing for two top slots.