Over the decades, a flotilla of Mars spacecraft have relayed back to Earth freeze-frame portraits of a cold, dry, dusty and desolate planet. But Mars experts are becoming progressively more surprised as they observe a world in constant change. Evidence is mounting that the red planet bares witness to very young, water-related features. Mars has undergone episodic climate cycles that have caused dramatic changes to its surface. Some of these climate swings may have been fairly recent as measured in geologic time.