Liquid Water Found on the Moon?

ALSJ

122:54:35 Scott: (To himself) Okay; and roll it over. (Pause)

[Dave comes around to the northwest face of the boulder, hops down into the crater the boulder made when it landed, puts his right hand on the top, preparing to push it over, and then stops to examine the rock more closely.]

122:54:40 Scott: Oh; what's that in there? Oh, me. It looks like a breccia. It sure is. The top layer is a breccia. You can see it. (Pause)

[With the TV cable now loose, Fendell pans counter-clockwise and, consequently, we don't get to see Dave push the boulder over. The photographs he takes later indicate that it rolled on to what was the west face.]

[Scott - "When Fendell gave it a command earlier, it didn't move. Maybe it's now picking up that command and he doesn't want it to move."]

[Jones - "Or, he wants to finish the pan that he started and couldn't finish because the cable got hung up."]

[Scott - "As typical, everybody watching this would have a different idea of what to do with the TV camera. And poor Fendell, fortunately he's got a filter between him and all the people with the great ideas. But can't you imagine poor Ed sitting there in the Control Room and everybody in the viewing room having their own idea of where to point that camera? (Chuckling) We all want to put our fingers in the pie, right? That had to be funny, and frustrating"]

[We then watched a little more.]

[Scott - "See! You just said, 'Oh, Ed!' You want it pointed at us pushing the boulder over. I'd never thought about this before, but I can just see everybody down at the Control Center wanting to drive that camera."]

122:55:03 Scott: There, that baby's over! (Pause)

[Fendell finally reverses direction to go back to the boulder.]

122:55:08 Scott: (Probably having knocked his tongs over) Lose my tongs.

122:55:11 Irwin: Do you want me to bring the other tongs?

122:55:13 Scott: No, I can get them.

[Dave hops into position to try to get down to get the tongs, which are lying flat on the ground. Fendell zooms in on the boulder and we lose sight of Dave.]

122:55:19 Irwin: (Laughing) Let me get them with the scoop.

122:55:23 Scott: Yeah. (Pause) A couple of pictures, and we'll get some of that material (that was) underneath the rock. (Pause)

[Dave moves the gnomon and, after he places it on the soil which had been covered by the boulder, we can see it swinging dramatically from side to side.]

[Scott, from a 1996 letter - "I must have been in a big hurry!"]

[Jim crosses the field-of-view as he goes off to the right to retrieve Dave's dropped tongs.]

122:55:50 Scott: Oh, there's a great big glass bubble on that rock!

[Dave takes a stereopair, AS15-86- 11561 and 11562, stepping to his left between frames.]

Q: Does that mean there is ice?

A: There's something that is reflecting radar signals like ice.

Q: The geologist said it was ice.

A: Highly likely that it's ice. There may be other stuff mixed in with it. Carbon dioxide and things like that.

Q: What other things would give the polarization effect that you're reading now as possible water?

A: We looked at the possibility that it could be a funny arrangement of rocks and other things, but again, it really was so highly correlated with that angle and so highly localized with the South Pole, that the most likely explanation is something that is low loss, and ice is the most likely thing.

Q: Can you go over the one to ten percent again? I don't understand the difference between that and what's in the bottom of the crater and where the one to ten percent...

A: What we could measure, as far as the abundance of it, is we have the radar footprint in a certain area. What we can show is basically the amount of signature we get back, assuming that the ice on the moon reflects the way the ice on Mercury does which has been measured. We can estimate a percentage of the area that is "pure ice". We estimated that to be less than three- tenths of a percent of the area that we illuminated, so that's like 100 square kilometers.

Q: So the area that you illuminated, is that in the bottom of this crater?

A: We illuminated the whole area, this whole area was illuminated. So of the area we illuminated, we estimated about a third of the area was permanently shadowed. This is all in the paper, by the way, it's in the Science paper. So that percentage is reflecting like ice.

Q: So it's incorrect to talk of one pond or one lake...

A: Right.

Q: How far was the Apollo landing from this spot, and did the Apollo landings make a mistake by not looking in this area?

A: No. The Apollo landings were all close to the equator. The farthest away from the equator that we got on Apollo 15 was 26 degrees, and this is at 90 degrees south. That was designed primarily for safety reasons. On Apollo they wanted a free return trajectory; in case there was a problem with the spacecraft, the astronauts would just loop around the moon and come back. So it wasn't a mistake, they were sent to the equator by design.

Q: What do you think this would look like if you could go right down and see it? Would you see a fairly large pond here, other ponds all over the place, some ice in crevices and rocks?

A: You would probably see... First of all you wouldn't see anything because you'd be in the dark. But if you had a flashlight and you illuminated the surface, you would see a surface that looked not unlike any place else on the moon, but if you were to dig down into that and pull it up, you would find that there would be ice crystals contained in the interstices between the dust grains. So it's not a sheet or a pond. It's not an ice rink on the moon. It's basically ice mixed into the dirt.

Q: What's the presumptive volume of it then, and how did you discern that?

A: As I mentioned, what we can tell from looking at the radar return is roughly the area that is covered by this. Assuming it reflects ice like ice on Mercury -- making that assumption. That's been well looked at. Then in order to see this back scatter effect, this roadside reflector effect; it's estimated that we have to see some number of wavelengths of our radar into the ice. In reviewing the paper, several of the reviewers posited we probably need to see somewhere between 50 and 100 wavelengths. So our wavelength is about six inches. So at the thickest case, it's roughly 50 feet.

Q: That translates to what in volume?

A: We were very conservative in the press release, but if you take basically 100 square kilometers by roughly 50 feet, you get a volume of something like a quarter of a cubic mile, I think it's on that order. It's a considerable amount, but it's not a huge glacier or anything like that.

Q: Can you compare that with something you know?

A: It's a lake. A small lake.