OPPORTUNITY EXPLORES FOR 14 YEARS DISCOVERS EVIDENCE OF ANCIENT FLOWING WATER NARRATOR: Over 50 years of Mars exploration has revealed intriguing clues, suggesting Mars has a surprisingly watery past. ASHWIN VASAVADA: There’s a lot of evidence for ancient flowing water on Mars. For one thing, there’s a lot of rivers that once coursed across the surface that are now dry, today. There’s also evidence for floods that catastrophically scoured the surface. JOHN GROTZINGER: It’s undeniable that the early history of Mars was much wetter than it is today. STEVE SQUYRES: The surface of Mars is littered with an uncountable number of little round things. These “blueberries,” as we nicknamed them, are what geologists call “concretions.”