Astronauts Dave Scott and Jim Irwin are some 150 meters up Hadley Delta Mountain, getting ready to take a close look at one of the biggest boulders they've seen so far. This is exactly where they want to be. Apollo 15 is the first mission to explore the mountains of the moon.

A few minutes earlier, Jim had dismounted the Rover up-slope of the boulder to take a series of panoramic photos. Dave and Jim both thought the slope there was a little too steep for them to easily move about, so Dave remounted the Rover and drove it down-slope to a little less steep area.

As Dave gets off the Rover, he notices the Rover beginning to slip sideways down the mountain. He grabs it. "I think I'll get back on. Tell you what, Jim. We'd better abandon this one."

As Jim moves toward Dave, he takes a quick look at the boulder. "Dave, let me come down and hold our Rover and you come up and look at this. The rock has lot of green on it." Dave, and indeed, any other geologist that I know of, could not possibly resist. Can you imagine finding a green rock on the moon?

I have painted Jim, on his knees, keeping the Rover from sliding down the mountain, while Dave scrapes several samples off the top of the green boulder. Some time after the mission Dave would say, "at one point, Jim and I almost had Al Bean do a painting of this scene. If Al Bean were to do something that Jim and I thought was unique about our mission, what would it be? So, we talked about it, Jim and I. And we came up with the operation of the side of the hill."

"There was some great geology on that boulder, we're working in fine powder on an 18 degree slope which is about as steep a surface as could be safely worked on with the Apollo technology spacesuit, and the Rover was so light that it wanted to slide down the hill. How far would it have gone? Who knows? We were in a new situation."

When examined back on Earth, the samples turned out to contain tiny beads of green glass, derived from deep within the moon, that were sprayed onto the surface billions of years ago in volcanic eruptions called fire fountains. The green glass is one of the most precious and scientifically significant samples brought back by Apollo astronauts.