The Genesis Rock

Return To The LM

 

Station 4 at Dune Crater

Corrected Transcript and Commentary Copyright © 1996 by Eric M. Jones.
All rights reserved.
Scan credits in the Image Library
Last revised 19 September 2014.

[Readers should note that, during the drive to Dune, Dave and Jim concentrate on the traverse and upcoming events. Spur Crater is literally and figuratively behind them.]

[Scott, from the 1971 Technical Debrief - "It seemed like that was a very fruitful place to obtain samples. I wish we could have spent more time there sampling because I'm sure we'd have found more of the anorthositic type, or the plage. But time being what it was, we pressed on back with a thought in mind that we'd stop at Dune Crater to pick up a secondary sample and take care of that requirement."]

["Summarizing the observations of the rock types collected at the Front, we saw breccia and crystalline. That was about it. Did we see any good pieces of basalt?"]

[Irwin, from the 1971 Technical Debrief - "No. We didn't see that until we got down on the Dune."]

[Scott, from the 1971 Technical Debrief - "I think that's right. There wasn't much block distribution. There weren't very many. All along the Front, there were half a dozen blocks that you could see on the whole base of Hadley Delta. There were no mounds. Did that big boulder we sampled up there (at Station 6a) have a fillet?"]

[Irwin, from the 1971 Technical Debrief - "I don't remember, Dave; you'll have to look at the pictures."]

[Scott, from the 1971 Technical Debrief - "Any patterned ground that you remember?"]

[Irwin, from the 1971 Technical Debrief - "No."]

[Scott, from the 1971 Technical Debrief - "No apparent flows or slides."]

146:16:04 Allen: Okay; and standing by for a mark when you roll.

146:16:09 LM Crew: We're rolling.

146:16:12 Allen: Roger. (Pause)

146:16:18 Scott: Hey, your camera's loose on the swivel, Jim.

146:16:23 Irwin: No, I'm getting a pan, here. (Laughs)

146:16:25 Scott: Oh, really? Oh. That's an awful fast pan.

146:16:28 Irwin: No, I just wanted to make sure it was running.

146:16:31 Allen: Dave, you'll want to trend...

146:16:32 Irwin: The light's not working.

146:16:33 Allen: ...course 346, and it's about 1.7 clicks to Station 4.

146:16:42 Scott: Okay. I'm going to go down sort of slow here, Joe. Just to make sure we play it cool.

146:16:54 Allen: Sounds reasonable. (Long Pause) And, Jim. When you finish photography, we're standing by for a description.

146:17:43 Irwin: Well, I just had the camera running, Joe. Remind me to turn it off when it runs out of film.

146:17:47 Allen: Yes, sir. I've got a hack.

146:17:48 Irwin: We've got about half a mag on it.

146:17:50 Allen: Roger. And you're running at 12 frames per second, I imagine.

146:17:53 Irwin: I think I know what that is. (Responding to Joe) Right.

146:17:57 Scott: But we're going down-Sun (garbled). Down-Sun isn't going to be very good on the photography, Joe, because the zero phase just washes out completely.

[This statement indicates that, at the moment, they are driving cross-slope. At Station 7, they were parked at about AZ.6/77.8; Station 4 is at the south rim of Dune Crater at about BE.9/77.1; and the LM is at BS.4/73.3.]

146:18:21 Irwin: Well, we're heading directly downhill, now. We're cross-Sun.

146:18:25 Allen: Okay.

[Obviously, Dave made a turn and is now headed north.]

146:18:31 Scott: Hey, are we looking at the big crater dead ahead?

146:18:33 Irwin: Is Dune, yeah.

146:18:34 Scott: Yeah.

146:18:35 Irwin: That should be Dune. (Pause)

146:18:40 Scott: You want to hit the...

146:18:41 Irwin: Southern (rim of Dune)...

146:18:42 Scott: Southwest

146:18:43 Irwin: Yeah

146:18:44 Scott: Yeah.

146:18:46 Irwin: But, again, that's...You know, we didn't see the levee, or rampart, on the eastern side.

146:18:54 Scott: No, we sure didn't.

146:18:57 Irwin: So probably any place on the southern rim would be good. (Pause) Although, from here, it almost looks like you could drive around the eastern rim of Dune. (Pause)

[Dune is the westernmost member of the South Cluster and a drive around the east rim would take them into the heart of the Cluster. Pre-mission photos suggested that there might not be any reasonably level path, particularly on the northeast side of Dune where it adjoins Crescent Crater.]

146:20:06 Allen: Roger. We copy.

146:20:07 Irwin: (Lost under Joe) our tracks here, as we go downslope.

146:20:16 Scott: Rover tracks!

146:20:23 Irwin: Probably just follow the tracks, huh?

146:20:24 Scott: Yeah, probably.

146:20:25 Irwin: To Dune. Yeah.

146:20:26 Allen: Sounds good. (Pause)

146:20:32 Scott: We know that's a fairly good route.

146:20:33 Irwin: Yeah.

[Scott - "One of the methods we seriously considered on getting back to the LM was following the tracks back because, if you're over the horizon and your Nav system doesn't work, it's very hard to tell where to go - other than the Sun compass that we had. We used to joke about the old Hansel and Gretel trick."]

[Jones - "But, once you were down there, did you also have the feeling that there were sufficient horizon features."]

[Scott - "Yeah, there are pretty good horizon features; but you can't beat the comfort of the tracks. And, if you're offset, horizon features don't necessarily work."]

146:20:42 Allen: Copied, Jim. Thank you. (Pause)

[These readouts indicate a location near BA.5/76.3. This location is roughly 400 meters west of the outbound track. Ken Rattee puts them near BB.3/77.5, a location which is about 430 meters from Station 7 on a heading of 350. This location is consistent with the range difference indicated by the Nav system since they left Station 7; and a heading of 350 agrees well with the suggested heading of 347 that Joe gave to Dave as they were leaving Station 7 at 146:16:33.]

146:20:55 Irwin: Yeah. (Pause)

146:21:02 Scott: Yeah, we're about down out of it, now. What a beautiful sight. Man! Well, we didn't get the 500 in stereo up there, but you got a pan, didn't you?

146:21:16 Irwin: Yeah.

146:21:17 Scott: Okay. (Pause)

[They had planned to get sets of 500-mm photographs taken at two different stops. Jim's 70-mm pans will serve the purpose, albeit at lower resolution.]

146:21:26 Irwin: Boy, I can't get over those lineations, that layering at Mount Hadley.

146:21:29 Scott: Boy, I can't either. That's really spectacular.

146:21:31 Irwin: That's really beautiful. Talk about organization!

146:21:36 Scott: Yeah, man!

146:21:37 Irwin: That's the most organized mountain I've ever seen.

146:21:40 Scott: (Laughing) Yeah, they're so uniform in width.

146:21:44 Irwin: Yeah.

146:21:45 Scott: Nothing we've seen before (during training) has had the same thickness of each bed. Yet those are...

146:21:54 Irwin: Uniform thickness from the very top to the bottom.

146:21:57 Scott: Yeah.

[500-mm frame AS15-84- 11320, taken from Station 6, shows the lineations near the summit of Mt. Hadley.]

146:22:09 Allen: Roger, Jim; copy. Any idea of the dimension on that thickness?

146:22:20 Irwin: Actually, I'd estimate it's relatively thin.

[In the following, Dave apparently thinks that Jim is talking about the diagonal lineations on Mt. Hadley. During the mission review, Dave and I had the impression that Jim was taking about the "high water marks" at the base of the mountain.]

146:22:48 Irwin: Yeah. Certainly less than 1 (percent).

146:22:50 Scott: Yeah. If you look across the ridge line and then look at the dip to the northwest there, you could count a couple of hundred, anyway; couldn't you?

146:22:59 Irwin: Yeah.

146:23:02 Allen: Amazing.

146:23:03 Irwin: Apparently you couldn't see that on TV.

146:23:06 Allen: No, not at all...

146:23:07 Irwin: Yeah, I wouldn't think they'd be able to make out detail like that.

146:23:08 Allen: ...Not at all. Hopefully, it's in the photographs, but we're marking it down...

146:23:10 Scott: Yeah.

146:23:11 Allen: ...none the less. (Pause) That TV isn't everything.

146:23:18 Scott: And then, Jim, if you look horizontal, well, all the way up, I guess that...

146:23:25 Irwin: Yeah.

146:23:26 Scott: ...would be slumping.

146:23:27 Irwin: Yeah, there is. I see it now. Yeah.

146:23:29 Scott: It just looks like slump, probably.

146:23:30 Irwin: Yeah.

146:23:31 Scott: Because they're discontinuous, subhorizontal lines, which are pretty much cross-bedded, if it was bedding, and I don't think it is. It just looks like slump-pattern ground. (Pause)

[Dave may be referring to the features just below the ridge line in AS15-84- 11321.]

146:23:56 Irwin: Oh, we're going at about point-8 clicks.

146:23:59 Scott: (Laughing as he defends his honor) Oh! No, no. "Eight."

146:24:02 Allen: Roger. Copied "Eight".

146:24:03 Scott: (Laughing) "Point 8!" That's almost backing up.

[They have an analog readout for speed and digital readouts for range bearing, distance, and range. See, also, a pre-shipment Boeing photo of the flight Rover.]

146:24:33 Allen: Roger. Copying every word, Jim. Keep talking. (Pause)

[The indicated location is near BC.1/76.3. The change in range since they left Station 7 and the heading combine to suggest a location nearer BC.7/77.0.]

146:25:10 Irwin: There's the LM directly ahead of us.

146:25:12 Scott: Yep.

146:25:13 Irwin: Bearing is...Yeah, bearing is right on. Right on the money.

[Here, Jim is noting that the bearing and heading agree perfectly. The LM is at BS.4/73.3 and, if Dave and Jim are currently at BC.7/77.0, the bearing to the LM should be 346 and the range should be 3.8 km. Although errors in the nav system are of interest when trying to plot an accurate traverse path, in terms of finding the LM or, once the map location of the LM was known, a planned geology stop, the errors were of little consequence given that the astronauts can get close and then drive around for a few moments if necessary. ]

[During the mission review, Dave was intrigued by the fact that, although they were at a range of 3.9 kilometers, they could see the LM. He suggested that I do the relevant calculations. So, here goes. The Moon has an average radius of R = 1738 km and, if it were a smooth, perfect sphere, the distance of the horizon (in km) for an observer with his eyes X meters above the surface would be sqrt(2 * X * R / 1000) = 1.86 sqrt(X). Similarly, a second observer would be able to see the first observer if they were separated by a distance less than the sum of their horizon distances. Photo AS15-85- 11471 shows Dave seated on the Rover and, knowing that the distance from the forward edge of the front wheels to the aft edge of the rear wheels is 3.1 meters, we can estimate that his eyes are about 1.7 meters off the ground. On a perfectly spherical Moon, his horizon distance would be 2.4 kilometers. Similarly, the top of the LM is 7 meters above the surface and, consequently, its horizon distance is 4.9 km. The net result is that, on a perfectly spherical Moon, Dave and Jim would be able to see the top of the LM at a range of 7.3 kilometers and - with perfect eyesight - the footpads at 2.4 km. At their present range of 3.9 km, on a perfectly spherical Moon they would be able to see the top 0.6 meters of the LM. And, finally, if they were on a rise of at least 4.4 meter, at a range of 3.9 km, they would be able to see the entire LM.]

146:25:41 Allen: Roger, Jim. Copy. And are you progressing towards Dune Crater now?

146:25:48 Irwin: Yes. Well, we're following our tracks. We thought when we got up here just south of Dune, we'd probably head north-northeast.

146:26:00 Scott: Big boulder on the surface. About a foot.

146:26:06 Allen: Okay, Jim. Copy...

146:26:08 Irwin: (Lost under Joe) awhile.

146:26:09 Allen: ...And just a factor into your thinking, we can afford a very short stop in the vicinity of Station 4. It doesn't have to be really very close (to the planned stopping place). We're interested in either documented samples or a rake sample there, if you think it looks like a good area for a rake sample.

146:26:30 Scott: Okay. Understand, Joe.

146:26:33 Irwin: But you'd still like the station to be on the southern rim, I would think.

146:26:38 Scott: Sure!

146:26:39 Irwin: Yeah.

146:26:40 Allen: Probably downwind...

146:26:41 Irwin: Like at Autolycus.

146:26:42 Allen: ...from Aristillus...

146:26:43 Scott: Why don't you head for right there, Jim?

146:26:44 Allen: ...or Autolycus, Jim, but the exact position's certainly not critical. Your judgment.

146:26:51 Irwin: Okay.

146:26:52 Scott: Okay. We'll go get some.

[They are hoping to find some of the Autolycus/Aristillus ejecta which, presumably, dug the South Cluster. Those craters are a few hundred kilometers north of Hadley and, if any pieces of these low-velocity impactors have survived, the thought was that momentum would most likely put them near the south rims of Dune and the other craters.]

[Scott, from the 1971 Technical Debrief - "Let's see, (reading from a list of questions) 'in approaching Station 4, did you get the feel of any buildup on the down-sweep (south) side of the secondaries? Did you get any directional kind of feel for those secondaries?' I didn't."]

[Irwin, from the 1971 Technical Debrief - "No. But it was just obvious that we were coming into an ejecta pattern there from Dune Crater. Concentrations of rocks increased as we approached the rim."]

[Scott, from the 1971 Technical Debrief - "But I didn't notice any grain-size difference. When we talk about grain size, I don't believe the grain-size change would be obvious to the eye. If there is any difference in grain size, it's probably micro, because I never noticed any."]

[Irwin, from the 1971 Technical Debrief - "It's hard to see when you're driving."]

146:26:58 Scott: Yeah, I think you're right.

146:27:02 Irwin: Okay, we're heading off now at (a heading of) 025. Heading directly toward the southern rim of Dune. (Pause)

146:27:21 Allen: Rover, this is Houston.

146:27:26 Scott: Go ahead.

146:27:28 Allen: Roger. The mag's run out on your camera, Jim. You should shut that off, and we don't want you to stray too far from your Rover tracks. Head back more or less the way you came. We have time for about a 10-minute stop someplace south and perhaps a little west of Dune Crater. Over.

146:27:48 Scott: Rog, Joe. We'll do that. We're just on the rim of Dune right now.

[Scott, from the 1971 Technical Debrief - "It was interesting to us concerning the ground's interest in finding our tracks. Every time we headed back from any point, they said, 'Find your tracks and follow them.' I guess there was some doubt as to the Rover Nav system, but I felt very comfortable about where we were. I never felt that we needed to find our tracks. Did you?"]

[Irwin, from the 1971 Technical Debrief - "No. Particularly from the Front, because we could see the LM."]

[Scott, from the 1971 Technical Debrief - "Another factor was the mountains in the background and the horizon. We could pick a point on the mountain and drive towards that point and we knew we were going toward the LM. I never felt disoriented or lost. I think we could have completely lost the Rover Nav system and I wouldn't have had any apprehension about finding the LM."]

[Irwin, from the 1971 Technical Debrief - "Yes; as you remarked, you could see Pluton all the way back. Just head toward Pluton."]

[Scott, from the 1971 Technical Debrief - "We could see Pluton, and we knew the LM was on a slight rise; topographic high, anyway. So I didn't feel tracks were necessary. As a matter of fact, I think we deviated from the tracks to find better routes, or more direct routes."]

[Irwin, from the 1971 Technical Debrief - "Yes. We certainly did on EVA-3."]

[Scott, from the 1971 Technical Debrief - "Well, on EVA-2, also. After Station 4, if we had followed out tracks, we would have had to do some weaving in and out of the craters there."]

[Scott, from a 1996 letter - " (With regard to horizon features), once you see the LM and locate it relative to a distant feature, then you can track the feature and reach the LM without seeing it again."]

146:27:58 Irwin: I did, Joe, but apparently it didn't run past...I still have about 45 percent left.

146:28:14 Allen: Okay, Jim. Fine.

146:28:20 Irwin: Yeah, I have turned it off.

146:28:24 Scott: This is a good spot right here.

146:28:27 Irwin: Boy, look at those large blocks on that west wall.

146:28:30 Scott: Yeah, man! Look at the large one right here. Okay, let me get this (seatbelt) off.

146:28:43 Allen: Standing by for your mark when you stop. And either Dave or Jim, we're going to need our (TV) camera and LCRU and the camera lens brushed off before you continue.

146:28:58 Scott: Okay.

146:28:59 Irwin: Okay; we've stopped, Joe.

146:29:00 Allen: Roger. Mark that.

146:29:01 Irwin: We're reading 292, (repeating the heading) 292, (bearing) 347, (distance driven) 8.9, (range) 3.4, 94, 100, 89, 90; motor temps, both low.

146:29:24 Allen: Okay; beautiful. (Long Pause)

[As indicated in the Station 4 sketch map, Figure 5-74 in the Apollo 15 Preliminary Science Report, they have parked about 40 meters south of the intersection of the rims of Dune and a younger, 100-m crater. They are virtually at the planned Station 4 location of BF.0/77.0. The Nav readouts give a position of BE.1/76.4, a position 270 meters SW of their actual location, as shown on Ken Rattee's map. This is very similar to the 290 meter error at Spur. When they get back to the LM at 147:09:22, the indicated error will be 200 meters SSW.]

146:29:43 Allen: Okay, Dave. And if you think you can make this a 10-minute stop, we'll forego the TV. We're interested in keeping it pretty short.

146:29:51 Scott: Let's forego the TV, Joe.

146:29:55 Allen: Okay. (Pause) And a rake might be useful...

146:30:00 Scott: Okay.

146:30:02 Allen: ...here, but once again,...

146:30:05 Irwin: The last ... ditch ahead.

146:30:07 Allen: ...your choice on getting us a few samples.

146:30:09 Irwin: For a 10-minute stop, Dave, I don't think the rake is...

146:30:12 Scott: No.

146:30:13 Irwin: ...very good.

146:30:19 Allen: Just depending on however you read the fragment(-size) distribution.

146:30:26 Scott: Yeah.

146:30:27 Irwin: There are a lot of large fragments here, Joe.

146:30:31 Scott: Jim, I've got to change my film Mag here.

146:30:33 Irwin: Okay; I'll take a pan.

146:30:35 Scott: Take a pan, yeah. Good idea.

[Comm Break]

[Jim's Station 4 partial pan (assembled by David Harland) is AS15-90- 12237 to 12248.]

[Mike Constantine has assembled a high-resolution version ( 745k ).]

[Frames 12237 and 12238 are down-Sun views.]

[In frame 12239, the western rim of Dune Crater is at the right edge of the picture. Hill 305 is on the horizon. Frames 12240 and 12241 show some of the large boulders on the rim of Dune Crater.]

[Frame 12242 shows the large Station 4 boulder on the rim of Dune Crater. The large vesicles are a few inches across. Vesicles are the imprints of gas bubbles trapped in the rock as it cooled and are usually found at the top of a lava flow. As is indicated in a detail, there is a line of outcrops on the far wall which may represent the upper portions of the mare lavas underlying the regolith.]

[Frames 12243 and 12244 show the eastern portions of Dune Crater, with Mt. Hadley in the background. Note the prominent lineations on the mountain.]

[Frames 12245 to 12248 show the Swann Range.]

146:32:28 Scott: Jimmy? (Pause)

146:32:34 Irwin: Camera's stopped working.

146:32:36 Scott: It has? Maybe you're out of film.

146:32:41 Irwin: I just put this on! (Pause)

[Frame AS15-84- 11248, the last one in Jim's partial pan, is only the 70th frame on this magazine. The following is taken from the Apollo 15 Mission Report.]

["Near the end of the second EVA, the (LMP's) 70-mm camera ceased to advance film. The crew reported that the camera was again operational after return to the lunar module. The camera was again used on the third EVA; however, after a short series of exposures had been made, the failure recurred. The camera was used for additional photography during the TransEarth phase without recurrence of the problem. Post flight analysis of the hardware included operational testing, disassembly and inspection, and measurement of battery charge. Operational testing with film loads indicated proper film advancement until approximately 200 cycles had been accumulated, at which time the failure mode was duplicated several times in succession. The film did not advance, although the motor was running. Disassembly and examination of the drive mechanism showed that the two set screws in the drive pinion were slipping on the motor shaft."]

["After the last use of the camera during the mission, the crew had difficulty removing the magazine. This was caused by a rivet which had become detached from the camera magazine latch mechanism."]

["Corrective action is as follows: flats will be ground on the motor shaft. A locking compound will be applied to the set screws when they are properly torqued against the flats. Also, epoxy will be applied to the tops of the screws to prevent them from backing off."]

[In a 1996 letter, Dave suggested that an additional factor in the failure may have been the fact that "the cameras had probably never been this hot for this long. They were a real heat sink."]

[Excessive heating could have contributed to slippage of the set screws but, no matter what the details were, the fixes were successful and no camera problems of this type occurred on either Apollo 16 or 17.]

146:32:46 Scott: Well, I'll take the (sample documentation) pictures. Let's get one sample. (Answering Joe) Jim's out of film, or his camera stopped, and I can take the pictures.

146:32:56 Allen: Dave...

146:32:57 Scott: Why don't we move it over here to a...

146:32:58 Allen: ...did you change your mag out at the last stop? Yeah, I guess you did. Beautiful! Press on.

[Obviously, Joe missed Dave's transmission at 146:30:31 about changing his film magazine.]

146:33:08 Irwin: Okay.

[Before they head for the boulders at the rim of Dune, they do some sampling near left-rear wheel of the Rover. Figure 5-74 from the Apollo 15 Preliminary Science Report indicates the location. Figure 5-76 details the locations of the collected samples.]

146:33:20 Irwin: Joe, I have a partial pan there, and my camera stopped working.

146:33:25 Allen: Okay, Jim. No problem. (Long Pause)

[Dave is probably putting the gnomon in position.]

146:33:52 Irwin: Okay, you're going to have to take the pictures.

146:33:53 Scott: Yeah, I'll take all the pictures, if you'll get the...(Long Pause)

[Dave takes a cross-Sun stereopair, AS15-87- 11759 and 11760, and a down-Sun, 11761.]

146:34:20 Irwin: Yeah. (Pause)

146:34:29 Scott: Okay, let me get another one (meaning another sample). (Pause)

146:34:39 Irwin: I got it.

146:34:41 Scott: Give me the bag and you get some soil here. Watch that big one. I want to get that one, too. (Pause as Jim puts some soil in the bag, undoubtedly with the scoop) Okay; good. Why don't you zip the bag. And let me get that other big rock. (Pause)

[Dave's after of the first sample site is AS15-87- 11762. In a moment, Dave will collect the large rock which is just north of the gnomon leg.]

[The large rock is sample 15495, a 0.9 kg 'vuggy' basalt.]

[A "location" photograph is one with the sample in the foreground and the Rover, the LM, or a prominent horizon feature in the background. To take AS15-87- 11763, Dave simply raises his aim to get the horizon in the picture.]

[Jim has put the first sample bag in Dave's SCB. As they will mention shortly, it is bag number 203 and contains 250 grams of soil (sample 15471) and basalt samples 15475 and 15476. The locations of 15475, 76, and 95 are shown in Figure 1 of the 15471 write-up.]

146:36:01 Irwin: No, I don't.

146:36:02 Scott: Okay, hold this bag, and it's number 174.

146:36:07 Allen: Okay, Dave. Copy that. 174.

146:36:12 Scott: And there's one before that that came off Jim's bag rack (meaning Jim's pack of individual sample bags).

146:36:21 Allen: Rog. And was that an empty one?

146:36:22 Scott: That mine?

146:36:23 Irwin: Yeah. Read the number on my bag (meaning the top bag in the holder.)

146:36:37 Scott: (Responding to Joe) Joe, just...We'll get to you.

146:36:39 Allen: Okay.

146:36:32 Scott: There's 204 in there now. It must have been 203. Okay, back up a little bit, Jim, so I can get the ("after") picture. That a boy.

[Dave's after of the "large rock" that was near the gnomon leg is AS15-87- 11764.]

146:36:51 Irwin: The large gray one to your right with large vesicles in it.

146:36:55 Scott: Yeah, that big boulder. Yeah, man!

[They are heading for the large boulder on the rim of Dune.]

[Scott - "That Station 4 boulder was striking. I remember that."]

[David Harland has assembled a trio of pictures showing the Station 4 boulder.]

[Scott, from the 1971 Technical Debrief - "We got to Dune Crater and there was one obvious boulder with large vesicles right there in the southern side of the notch that we hadn't sampled. That was probably one of the most prominent rocks we saw during the whole time (on the Moon)."]

[Irwin, from the 1971 Technical Debrief - "I saw another rock with exactly the same size vesicles right at the edge of the rille (at Station 10)."]

[Scott, from the 1971 Technical Debrief - "You're right"]

[Irwin, from the 1971 Technical Debrief - "That was probably the bedrock."]

[Scott, from the 1971 Technical Debrief - "Yes, I'd say definitely it was bedrock. We sampled that one in the center near the vesicles, and on the edge where there were smaller vesicles on the outside of the rock. They were millimeter-size vesicles. That rock was about 6 feet high and 4 feet across, with rounded, 3-inch vesicles, very clean with plagioclase laths in it that were a centimeter long and a millimeter wide (and with) random orientation."]

146:37:00 Scott: (Let's) get to it. (Pause; approaching the large boulder) Huge vesicles. Oh, look at the plagioclase in there! Man, look at the laths, Jim; it's beautiful. Whooo! Vesicles in this must be about 2 to 3 inches...

146:37:22 Allen: Oh, yes.

146:37:23 Scott: ...in size. And it's a big boulder.

146:37:30 Allen: Okay, Dave, we're going to have to sack that one up and think about moving on.

146:37:36 Scott: Yes, sir. (Pause)

[Dave takes a series of photos of this large, basalt boulder. AS15-87- 11765 and 11766 are cross-Suns from the south. In taking 11766, Dave has raised his aim to show the upper parts of the boulder. Note the angle of Jim's adjustable scoop. Frames 11767 and 11768 are down-Suns; 11769 and 11770 are cross-Suns from the north.]

[Next, Dave moved in to get close-ups 11771 and 11772 and used his tongs to get the distance right.]

[Dave then moved to his right to get 11773 and 11774.]

146:37:46 Scott: Really is, isn't it?

146:37:47 Irwin: You going to try and knock a piece off, here?

146:37:48 Scott: Yeah.

146:37:50 Irwin: Should come off pretty easy.

146:37:51 Scott: Sure looks like it. (Pause) Get all these. (Pause) Okay, if you'll hold my tongs, here. (Pause, perhaps as he gets the hammer off Jim's PLSS) Okay. (Pause) Should be able to get it right here in the middle. (Pause) Piece. Got it. (Long Pause)

146:38:42 Irwin: Okay; that's enough, Dave.

146:38:43 Scott: I think you're right.

146:38:48 Allen: And we think you're right.

146:38:49 Scott: That one right there. (Pause) Okay, good show. Good shape. (Chuckling about the size of the piece he's knocked off) (I'll) put this (hammer) back (on Jim's PLSS).

146:39:16 Irwin: Now put that large one in my pack.

[The authors of Apollo 15 Voice Transcripts Pertaining to the Geology of the Landing Site, N.G. Bailey and G.E. Ulrich, suggest that the 'large one' may be sample 15498, which is a 2.34 kg breccia. It contains abundant clasts of mare basalt. However, as indicated in the Apollo 15 Lunar Sample Information Catalog, 15498 arrived at the Lunar Receiving Lab in SCB-6 which, at the beginning of EVA-2, was hanging of the geopallet at the back of the Rover. If Dave and Jim did collect 15498 at Dune, it seems more likely that the 'large' sample mentioned at 146:39:16 and 146:39:40 is 15499, the 2.0 kg piece of basalt Dave just broke off the top of the boulder. Where and when the latter was collected is unknown and, because of the lack of TV coverage, will probably never be known.]

146:39:25 Irwin: Uh...

[What they don't remember is that, just before they left Spur, Dave took the SCB with the anorthosite off Jim's PLSS but didn't replace it with another one. See the dialog following 146:43:37.]

146:39:39 Irwin: Son-of-a-gun.

146:39:40 Scott: Put that in my pack (SCB); will you, Jim? Okay; this is a large corner of a vesicular rock that's a big boulder sitting here.

[This is definitely 15499. It is undoubtedly the largest "chip" that any of the Apollo astronauts broke off a boulder.]

146:39:56 Scott: Is that right?

146:39:57 Irwin: Yeah, it's just about filled.

146:39:58 Scott: Okay. Hey, maybe...Let me get those two frags there from the center. Give me...

146:40:02 Irwin: Yeah.

146:40:03 Scott: ...those tongs. You can get out a bag.

146:40:06 Allen: Okay, Dave. And this should be...

146:40:07 Scott: This is the ... of anything we've seen.

146:40:08 Allen: ...the last one. We want to...

146:40:09 Irwin: By a long shot.

146:40:10 Allen: ...head them up and point them out.

146:40:12 Scott: Okay. "Head them up and point them out." (Bag) 204. Oh, let me get the other one. Two frags from the center of the...

146:40:26 Irwin: No, that's not it. Down...No.

[Jim has kept his eye on two fragments Dave knocked off the boulder earlier. They are samples 15485 and 86. Their original locations on the face of the boulder are indicated in Figure 3 in the write-up for sample 15499.]

146:40:30 Irwin: Down there. Right there. That's it.

146:40:36 Scott: 204 for the two frags in the center of the boulder. And the big chip off the top, that's got the vesicles in it, is in my pack, solo (meaning it is not bagged).

146:40:44 Allen: Roger.

146:40:50 Scott: And that's not much for Dune, but I think it's representative.

146:40:57 Allen: Okay. And we're ready to roll.

146:40:58 Scott: I hope it's representative because it...(Responding to Joe) Okay. Put that in my bag, Jim?

146:41:05 Irwin: Yeah. (Pause)

146:41:12 Scott: Got it?

146:41:13 Allen: And, Rover, you should be able to easily follow your tracks...

146:41:16 Scott: Huh?

146:41:17 Allen: ...back home.

146:41:21 Scott: Sure. I'm sure we can, Joe. (Pause) Okay, Jim. Head back to the Rover.

146:41:37 Irwin: Okay. (Pause)

146:41:46 Scott: Boy, underneath that one is another one with larger vesicles in it. (Long Pause)

[This may be the point at which Dave takes AS15-87- 11777 to 11779.]

[Scott, from the 1971 Technical Debrief - "In contact with that (6-foot rock on the surface) was a highly vesicular-like - maybe half-centimeter (vesicles) - uniform, spherical, vesicular rock, which was a lighter gray and had not been chipped. I took a picture of it. It's too bad we didn't get to sample it. But, it was a different (lava) flow, entirely. A different rock, and they were in contact."]

146:42:41 Irwin: Okay, I'm reading pressure, 3.85 (psi); (warning) flags are clear, and 50 percent (oxygen remaining).

146:42:49 Scott: Okay. Dust off (the RCU) a little bit here. I'm reading 42 percent, about 3.9, and - (if I can get the) dust off - flags are clear!

146:43:09 Allen: Sounds good.

146:43:10 Scott: Okay. Jim. Let me have a seatbelt. Ooh! Easy, easy, easy!

146:43:18 Allen: Jim, when you get settled, you can check the camera on 12 frames per second and turn it on again, please.

146:43:29 Irwin: Yeah. I don't know why it didn't come on last time, Joe.

146:43:31 Allen: Okay, check it at 12 frames per second, please.

146:43:33 Irwin: Try it again.

146:43:37 Scott: Just sit back as you can now. Can you hold these things for me, Jim? Hold those, too. (Pause) There. You're in. (Pause) (Thinking about the missing SCB) Oh, no; I didn't put a bag on you, did I? Yeah, that's right. We're okay!

146:44:12 Irwin: What did you do with that bag?

146:44:13 Scott: I stuck it on the Hand Tool Carrier so it -

146:44:15 Irwin: That's right.

146:44:16 Scott: Yeah.

146:44:17 Irwin: Okay. Boy, you had me worried.

146:44:18 Scott: Well, I had me worried, too. I knew the one with the good rocks, I hadn't lost, because I stuck that in the seat pan. But I thought I'd put one on you, and now I remember I started to put it on you, and your harness looked loose, so I stuck it on the handtool carrier where it's got a lock. So we're okay.

146:44:35 Allen: And we knew all the time, Dave. We should have told you. (Pause) Wanted to keep you honest, though.

146:44:42 Scott: All right, Joe. Keeps us honest. Okay.

146:44:51 Irwin: Okay, it looks like the camera is working, Joe. It's just hard to press that in all the way.

146:45:03 Irwin: We'll try it again on our drive back.

146:45:05 Allen: Okay, Jim. Sounds good. We'll be standing by for your mark.

146:45:13 Scott: Okay, I'm on. Get my handy-dandy seatbelt. (Long Pause) Okay. Seatbelt's fastened. I think I'm finally learning how to do that. Okay. (Pause) Okay, Joe. Mark. We're rolling.

[Dave parked the Rover at 146:28:59 and, consequently, this has been a 17-minute "10-minute station". He parked the Rover on a heading of 292. Frame AS15-87-11780 was taken from Dave's seat, probably accidentally and probably at Station 4. Certainly it shows a view somewhat north of west. Note the dust smudge on the lens.]

[Scott, from a 1996 letter - "Although it was a limiting factor, the clock was not the objective. The objective was to do some good geology quickly. We could have easily limited the stop to ten minutes - but without doing much geology. The ground rules gave us some flexibility; and we used it! Joe was getting pretty anxious; and we should have made a deal: stay at Dune longer and drive back faster. Dune was another great place!!"]

[Scott, from the 1971 Technical Debrief - "The other frags (than the one's off the boulder) we picked up at Dune Crater, we just didn't have time to look at. We didn't give them (meaning Houston) a TV stop there, either. When you cut down the time to the point we had, it's just too bad. We spent a lot of time there, too."]