Transcript:NARRATOR: Ken Edgett and Mike Malin are space photographers -- fascinated by what they see and learn from their images. But unlike other photographers, the cameras they use are millions and millions of miles away -- circling the red planet. The Mars Orbiter Camera is on the Mars Global Surveyor, orbiting the planet since 1997. The mission's longevity has allowed scientists to monitor a changing planet, which enabled the camera team to witness the appearance of craters where none existed before and see evidence of current water flows on the surface KEN EDGETT, MARS ORBITER CAMERA IMAGING TEAM MEMBER The thing that startles me The most is the idea that the water has flowed on Mars in this decade. One of these two sites that we observed, it had no new deposit in the gully in 2001 which is in this decade. We come back in 2005 and there this stuff, that was amazing. MIKE MALIN, MARS ORBITER CAMERA PRINCIPAL INVESTIGATOR We think what's actually happening is that there is ice formed in the rock acting as a dam and then water builds up behind that ice dam. And as the pressure of that water gets high enough it breaks through the dam and out comes a lot of water and debris that was forming the dam. For an astronaut or robotic vehicle, you wouldn't want to be in the gully at the time. Clearly that would be like being caught in a channel in the desert during a flash flood. EDGETT: Many of us have heard for years the mantra, follow the water. That's what NASA's Mars exploration is about. We now know where to look! NARRATOR: Using this before and after technique, the team made another very serendipitous discovery. Malin It was in a picture that had been taken as context for a higher resolution view and I had put in my notes-- why hadn't we taken a picture of the dark spot? And Ken's response was because it didn't exist! Narrator: It was an impact crater, a new one, formed in the last five-to-six years. Since then, they've found a total of 20 new craters in a relatively small area. Malin If someone were to live on Mars for about 20 years, the cratering rate is high enough that they would hear one of these events sometime during those 20 years. There are enough of these objects hitting, spread out statistically over the planet, that you would expect to hear one of these blasts when it hit the ground. That isn't happening on the Earth. Narrator: The findings add to Mars Global Surveyor’s legacy. The spacecraft is probably finished with its operating life, but it leaves a treasury of scientific discovery. MALIN: To find any evidence for liquid water today is mind boggling. Ken and I are explorers. We unfortunately have to use a surrogate vehicle. I think both of us would love to go to Mars and come back. But this is exploration and it’s a not just an intellectual activity. It's an emotional activity as well. NASA's Mars Reconnaissance Orbiter continues the work of Mars Global Surveyor, by taking pictures of this amazing planet at even higher resolutions.