The 50th Anniversary of the Genesis Rock – Watts Up With That?

Guest “How about that, geology fans?” by David Middleton

50 Years Ago: Apollo 15 on the Moon at Hadley-Apennine

David R. Scott, Commander
James B. Irwin, Lunar Module Pilot
Alfred M. Worden, Command Module Pilot

Backup Crew
Richard F. Gordon Jr., Commander
Harrison H. Schmitt, Lunar Module Pilot
Vance DeVoe Brand, Command Module Pilot


August 1, 2021 marked the 50th anniversary of the discovery of the “Genesis Rock”…

Genesis Rock

Published: September 22, 2017
On August 1, 1971, Apollo 15 mission commander David R. Scott relayed exciting news to Mission Control and the scientists in the back room.

“Guess what we just found,” Scott said. “Guess what we just found! I think we found what we came for.”

That sample, nicknamed the Genesis Rock, sample number 15415, was an anorthosite, a piece of the moon’s primordial crust. Geologists, hoping to learn more about the moon and its origins, selected the Hadley-Apennines landing site for precisely this reason. While not the oldest lunar sample brought back from the moon, geologists at the Manned Spacecraft Center (now known as the Johnson Space Center) later concluded that this rock was about 4 billion years old.

Apollo 15 was the first of three J missions, often called the true scientific missions to the moon.

These missions featured the Lunar Rover equipped with a television camera, a redesigned Lunar Module (LM) that allowed the crews to stay for extended periods on the moon and long duration backpacks for the moonwalkers allowing astronauts to spend more time exploring the lunar surface. Engineers also made changes to the Service Module, filling it with remote sensing instruments designed to document the moon’s surface. During the crew’s three spacewalks, Scott and James B. Irwin spent almost nineteen hours exploring the moon and covered 17.5 miles of lunar terrain in the lunar rover.

To prepare for this historic flight, the crew trained for months. An important part of that training included geology field trips with geologists from universities and the center as well as the U.S. Geological Survey. Apollo 15, 16 and 17 crews dedicated much more time to these exercises than their colleagues on the earlier Apollo lunar landings.

Apollo 15 astronauts traveled to a different geological site each month, which amounted to about 18 trips, compared to five or six for the previous flight of Apollo 14. Scott and Irwin practiced in terrain similar to the conditions they would find on the moon and within the limitations they would face on the surface. Gary E. Lofgren helped train the Apollo 15 crew and now serves as the lunar curator.

“You’d draw a circle around how far they could go,” Lofgren explained. “So this is the area that they can move around in. They couldn’t get farther from the LM than a certain distance … The amount of area that they could traverse was pretty small. We would pick out spots, and then we would tell them to collect the kinds of samples that were obvious to collect at that site: collect a sample of the soil and a sample of the rocks.”

During these traverses the crew gained skills in identifying rocks, describing terrain, documenting samples as well as proper sampling techniques. Sometimes they test drove Grover, a one-G rover.

CapCom Joseph P. Allen and scientists also gained valuable experience as they sat in a separate simulated control room and science support room. Scott and Irwin communicated by radio to Allen, as they would during their flight. Following the simulation, instructors who walked along with the two men pointed out what they had overlooked in their traverse.

In preparation for their landing in the Hadley-Apennine region, the instructors along with Scott and Irwin, visited volcanic sites like Hawaii and areas “where they would see the kinds of rocks we expected to find as part of that primitive crust,” Lofgren noted.

These sites included the San Gabriel Mountains, Ely, Minnesota, the Rio Grande Gorge and the San Juan Mountains. Their training paid off in spades. Leon T. Silver, an Apollo 15 instructor from Cal Tech, called the mission the “apotheosis of all the things we’d been planning to do… it was the coming together of developing the technical capabilities, preparing men to be explorers as well as many, many other things.”

He and others were confident that they would find a piece of the ancient crust. Why did these scientists place such faith in two former test pilots?

“Well,” he explained, “that’s because the human intention, well educated, well prepared, can squeeze things out, you understand?”

For more information on this significant flight, read some selected oral history interview excerpts available on the JSC History Portal:


Apollo 15 Commander Dave Scott and the Genesis rock. Image Credit: NASA

Here’s the communication transcript of the discovery of the Genesis Rock (CDR = Commander Dave Scott, LMP = Lunar Module Pilot Jim Irwin):

CDR Okay. Now let’s go down and get that unusual one. Look at the little crater here, and the one that’s facing us. There is this little white corner to the thing. What do you think the best way to sample it would be?

LMP I think probably – could we break off a piece of the clod underneath it? Or I guess you could probably lift that top fragment off.

CDR Yes. Let me try. Yes. Sure can. And it’s a white clast, and it’s about – oh, boy!

LMP Look at the – glint. Almost see twinning in there.

CDR Guess what we found? Guess what we just found?

LMP I think we found what we came for.

CDR Crystal rock, huh? Yes, sir. You better believe it. Look at the plag in there. Almost all plag – as a matter of fact – oh, boy, I think we might – ourselves something close to anorthosite, because its crystalline and there’s just a bunch – it’s just almost all plag. What a beaut.

LMP That really is a beauty. And, there’s another one down there.

CDR Yes. We’ll get some of these. – – – No, let’s don’t mix them – let’s make this a special one. I’ll zip it up. Make this bag 196, a special bag. Our first one. Don’t lose your bag now, Jim. O, boy!


“Plag” refers to plagioclase, the dominant mineralogy of anorthosite. The Genesis Rock was sitting on top of a mound of glass-matrix breccia and/or regolith clods (AKA The Pedestal), almost as if it had been intentionally placed there for the Apollo 15 astronauts to find.

The Genesis Rock was sitting on top of the mound (The Pedestal), just to the let of the center of this photo. 15435 LPI.

Transearth Coast Press Conference

CC Q2: Near Spur Crater, you found what may be “Genesis Rock”, the oldest yet collected on the Moon. Tell us more about it.

CDR: Well, I think the one you’re referring to was what we felt was almost entirely plagioclase or perhaps anorthosite. And it was a small fragment sitting on top of a dark brown larger fragment, almost like on a pedestal. And Jim and I were quite impressed with the fact that it was there, apparently waiting for us. And we hoped to find more of it, and, I’m sure, had we more time at that site, that we would have been able to find more. But I think this one rock, if it is, in fact, the beginning of the Moon, will tell us an awful lot. And we’ll leave it up to the experts to analyze it when we get back, to determine its origin.

Lunar and Planetary Institute

How’s that for luck? Without the field geology training they had received from geologists like Lee Silver and Apollo 17 astronaut Jack Schmitt, the luck wouldn’t have mattered; because they wouldn’t have known what to look for.

As it turned out, the Genesis Rock wasn’t as old as they had initially assumed; but it was a very significant find.

Ferroan Anorthosite
269.4 grams

Lunar anorthosite 15415 was found perched on a clod of soil breccia (15435) on the rim of Spur Crater (Wilshire et al. 1972). Spur Crater is about 50 meters above the mare surface on the slope of Hadley Delta.
It is subdued in nature and apparently old. The samples collected from Spur Crater had a range of exposure ages indicating that the material excavated may have been pre-exposed and/or may include material added from other sources after the Spur event (Arvidson et al. 1975).

During a Transearth Coast press conference, 15415 was called “Genesis Rock” and the name has stuck in spite of the fact that it may not be the oldest rock from the Moon. The astronauts correctly recognized that it was coarse-grained, made almost entirely of plagioclase and probably from the lunar highlands (figure 1). Thin sections also show that it is an anorthosite made almost entirely of coarse-grained plagioclase (figure 2) and that it is only mildly shocked. Age dating proved difficult, but an age of about 4 b.y. was determined by the Ar plateau method. However, the very low initial 87Sr/86Sr ratio attests to it great antiquity and the lack of meteoritical siderophiles proves its pristinity (lack of contamination by impacts).

In summary, 15415 is a unique lunar sample, in that, it is a pristine coarse-grained, unbrecciated anorthosite made up of mostly (98%) calcic plagioclase (An96). For a rock to have this much plagioclase, the rock must have formed by a process of plagioclase accumulation. It is generally understood that the original crust of the moon formed by plagioclase floatation from a magma ocean (see Warren 1985). But the exact connection of 15415 to this process is unclear, because Ar dating of 15415 showed it to be too young to have formed from the original lunar magma ocean.

Ryder (1985) provided a comprehensive review of all aspects of 15415. The section on 15435 provides a
picture of the sample on the moon.

Lunar and Planetary Institute

Photo of Genesis rock before processing. Cube is 1 inch. Image Credit: NASA

Anyone who is interested in the mineralogical, petrological and geochemical analyses of the lunar rock and regolith samples brought back to Earth by the Apollo astronauts, as well as the Russian Luna missions, can access them here: Lunar Samples.

For those with less interest in igneous petrology, and just interested in how cool field geology is, I highly recommend the HBO miniseries, From the Earth to the Moon, episode 10, Galileo Was Right. For a detailed review of the field and aerial geology training see Science Training History of the Apollo Astronauts by William C. Phinney. The aerial geology training of the Command Module Pilots was particularly important.

One of the significant results of this training was Worden’s orbital observations during the actual mission of what he suggested were cinder fields in the Littrow area. This became a major factor in the selection of Taurus Littrow as the landing site for Apollo 17.

In the Technical Debriefing following the mission Worden indicated that “I thought that the training that I received in orbital geology was better than I had anticipated. I was very well prepared when I got there. The only comment that I’d have is that most of that detailed training we had came late in the game. It had to be sandwiched in with other things at the Cape…It would be helpful if we got into the detailed part of that a little bit earlier in the training cycle” (p. 17-10).

Science Training History of the Apollo Astronauts, page 146

The astronauts particularly enjoyed the field trips.

The attitude of the crew is reflected in the comments of Commander Dave Scott: “Another vital focus of our training was the intensive preparation for the geological investigations we would be carrying out. This meant field trips. I loved them. I loved to be outdoors. It was a chance to get away from the simulators and other hardware for three days at a time, a chance to have a few beers in the evening after a hard day in the field.”

Science Training History of the Apollo Astronauts, page 115

Field geology rocks!

Now, on to the rille…

Hadley Rille

“Fendell” refers to Ed Fendell, who remotely operated the LRV camera from mission control in Houston. “Allen” refers to CapCom Joseph Allen. Joe was the astronaut at mission control tasked with verbal communications with the Apollo 15 crew, he subsequently flew on space shuttle missions STS-5 and STS-51_A. “Jones” refers to Eric M. Jones, author of the transcript and his running commentary with Dave Scott.

165:22:40 Scott: And, I have the 500 out.

165:22:42 Allen: And look at that rille.

[Fendell is currently looking toward the northwest.]

165:22:47 Scott: How about that?

165:22:48 Allen: How about that, geology fans?

[North of the Rover, Jim has just finished a pan consisting of frames AS15-82- 11110 to 11127.]

[Frame 11110 shows the far wall of Hadley Rille with Hill 305 in the background.]

[Frame 11113 shows the view to the north and the slope of the mare surface toward the rille. ]

[Frame 11116 shows the view toward Mt. Hadley, which is partially obscured by the local horizon. Note that the lineations on the mountain are still faintly visible.]

[Frame 11117 shows the view toward the Swann Range with numerous, partially-buried boulders in the foreground.]

[In frame 11120 we see Dave at his side of the Rover, with his seat raised as he gets the 500-mm camera.]

[Frame 11121 is an excellent view south along the rille. Dave is reaching under his Rover seat to get the 500-mm camera. Note that the front section of the left front fender seems to be missing. {See the discussion at 148:55:33 and a Summary provided by Ron Creel ( 1.3 Mb PDF ) of the fender extension losses that occurred on all three Rover missions.} Note, also, the appearance of Silver Spur at the upper right and compare with Dave’s 500-mm image of Silver Spur, AS15-82-11250 taken during the SEVA at a similar viewing angle but a much lower sun elevation. See, also, a discussion of the appearance of Silver Spur in the Apollo 15 Preliminary Science Report.]

[Frame 11122 is an excellent picture toward the south, showing the bend of the rille near Elbow Crater. See a labeled detail. David Harland has combined high-resolution scans of 11121 and 11122 in a portrait of Dave at work.]

[Frame 11123 is centered on St. George Crater.]

[Frames 11124 and 11125 show the west wall of Hadley Rille. In 11125, note the foreground boulder one fiducial right and below center with horizontal structure.]

[Frame 11126 is centered on that boulder.]

[Frame 11127 ends Jim’s pan.]

[Jim crosses the TV field-of-view headed for the Rover.]

165:22:50 Scott: I can see from up at the top of the rille down, there’s debris all the way. And, it looks like some outcrops directly at about 11 o’clock to the Sun line. It looks like a layer. About 5 percent of the rille wall (height), with a vertical face on it. And, within the vertical face, I can see other small lineations, horizontal about maybe 10 percent of that unit.

[Dave’s 500-mm photo AS15-89- 12115 shows one of these outcrop just below the central fiducial. David Harland’s assembly of 500-mm frames AS15-89-12016 to 12042 shows the entire area. Jim goes to the back of the Rover to get his scoop.]

165:23:26 Scott: And that unit outcrops (at various places) along the rille. It’s about 10 percent from the top, and it’s somewhat irregular; but it looks to be a continuous layer. It may be portions of (mare basalt) flows, but they’re generally at about the 10-percent level. I can see another one at about 12 o’clock to the Sun line, which is somewhat thinner, maybe 5 percent of the total depth of the rille. However, it has a more-well-defined internal layering of about 10 percent of its thickness. I can see maybe 10 very well-defined layers within that unit.

[The rille is about 350 meters deep in the area of Stations 9 and 10, so 10 percent of the depth corresponds to about 35 meters.]

Video Clip  2 min 39 sec ( 0.7 Mb RealVideo or 24 Mb MPG )

165:24:12 Allen: Beautiful, Dave, beautiful.

[During Dave’s last transmission, Jim moved north of the Rover to start sampling. Fendell reaches the clockwise pan limit, he is looking virtually up-Sun over the right corner (left, from our perspective) of Jim’s seat.]

[Dave and Jim spent quite a bit of time in the field learning how to do verbal descriptions. Here, Dave was primed to look for layering in the far wall because the layering would tell the geologists back home something about how the mare basalts were deposited.]

[Scott – “You probably noticed that I use percent rather than feet or some other finite measure. A lot of times, when we were doing field work, you really didn’t know what the feet were. Unless you know what the distance is, you can’t tell the feet. And (with training) it becomes very comfortable to do things in percent, because you can do it very quickly. And it’s pretty accurate because, knowing how deep the rille is, you can calculate the feet later. Whoever taught us the percent thing made it very easy to describe because you don’t have to go through ‘well, let’s see, it’s a little over a mile over there…’. That’s a lot of mental conversion.”]

[Jones – “With lots of room for error. Whereas, with this, bang, you’re there.”]

[Dave then mentioned that, before the flight, they had thought about how to use the 500 at this Station. See cuff checklist page CDR-27.]

[Scott – “The technique with the 500 was to get a horizontal sweep and a vertical sweep. From the place where Jim did the pan. That was the whole idea.”]

[Jones – “And the best examples of that are the Hadley pictures you took from Station 6, the 500s you took here, and the similar ones you took at Station 10.”]

165:24:14 Scott: As I go down the rille, below this upper layer at 10 percent, there seems to be mostly debris in the order of large angular fragments, maybe the largest being like 5 percent of the total depth of the rille.

[Frame AS15-89- 12117 shows the largest talus block in the Station 9a photos.]

165:24:38 Scott: And then they gradually break on down to very small fragments and a talus slope.

[Fendell reverses direction and starts panning counter-clockwise. After a short while, Jim returns to the Rover and Fendell gives us a look at Jim’s SCB while Jim does something at his seat.]

165:24:43 Scott: I see no significant collection of talus at any level. It seems to be fairly uniformly distributed in patches all the way down, to as far as I can see, to the bottom of the rille. In looking on to my 12:30 to 1 o’clock on up the rille…And, I guess we’ll get a little closer, when we get down to sampling it down there. Why, it looks very much the same. Outcrops of this one unit, irregularly spaced, discontinuous, but along the general 10 percent from the top line; with the talus sliding down into the bottom of the rille. I see no differences in color. However, the vertical section of the unit, which is exposed, looks to be somewhat lighter in gray. The blocks, which have fallen down into the talus, seem to have a more tan or different tone of gray color to them. Sort of like the fresh vertical section was more recently exposed. Let me let you digest that for a minute, and let me take a bunch of 500’s. I’ll get you the vertical and the horizontal and, boy, there’s lots of things to shoot at over there. (Pause) Hey, Jim, where’d you take the pan? Right over here?

165:26:17 Irwin: Where there’s a little circle (of disturbed soil) on the ground.


“How about that, geology fans?”

Lunar rilles are long, narrow depressions on the Moon’s surface. They can be linear or sinuous and often resemble dried river beds. They are most likely the result of collapsed lava tubes. Maybe the Artemis astronauts can help figure out how they formed.

Jul 26, 2021
Apollo to Artemis: Drilling on the Moon

By Leejay Lockhart
NASA’s Kennedy Space Center

Fifty years ago, Apollo 15 lifted off from Kennedy Space Center, sending Commander David R. Scott, Command Module Pilot Alfred M. Worden, and Lunar Module Pilot James B. Irwin on the first of three Apollo “J” missions. These missions gave astronauts the opportunity to explore the Moon for longer periods using upgraded and more plentiful scientific instruments than ever before. Apollo 15 was the first mission where astronauts used the Apollo Lunar Surface Drill (ALSD) and the Lunar Roving Vehicle (LRV).

Scott and Irwin would land on the Moon and use the ALSD at the site where they set up several scientific instruments during the nearly 67 hours they were on the surface of the Moon. The tool was a rotary-percussive drill that used a combined motion that hammered a rotating drill bit into the surface to make a hole. The overall purpose of gathering core samples was part of NASA’s lunar geology studies to learn more about the composition of the Moon and discover more about its history by looking at different kinds of rocks, including some from below the surface.

Now, NASA is going back to the Moon as part of the agency’s Artemis missions and has a new drill headed to the lunar surface as a commercially delivered payload via the Commercial Lunar Payload Services initiative. The Regolith and Ice Drill for Exploring New Terrain (TRIDENT) is key to locating ice and other resources on the Moon.

“Honeybee Robotics designed the TRIDENT drill for NASA to sample lunar regolith,” said Amy Eichenbaum, the Polar Resources Ice Mining Experiment-1 (PRIME-1) deputy project manager. “TRIDENT will help understand the physical properties of the lunar regolith while also allowing analysis of the resources present in samples taken from various depths.”

TRIDENT is also a rotary-percussive drill, but one major difference between it and its Apollo counterpart is that TRIDENT does not need astronauts to operate it manually. Honeybee Robotics originally partnered with NASA through the Small Business Innovation Research program, a highly competitive program that encourages small businesses to engage in federal research.

Polar Resources Ice Mining Experiment-1 (PRIME-1) will be the first in-situ resource utilization demonstration on the Moon. For the first time, NASA will robotically sample and analyze for ice from below the surface. PRIME-1 will use TRIDENT to drill in a single location at a site with a high likelihood of having water – whether in liquid or ice form. It will drill down about 3 feet (1 meter) below the surface, each time bringing up samples that NASA will analyze with a scientific instrument – the Mass Spectrometer observing lunar operations (MSolo).

“MSolo will measure water ice and other volatiles released from the sample brought to the surface by the TRIDENT drill,” said Dr. Janine Captain, the principal investigator for MSolo. “These measurements will help us start to understand the distribution of resources on the lunar surface, a key to enabling a long-term presence on the Moon.”

Apollo 15 landed near the Hadley Rille, a long, deep channel-like gorge in the Moon’s surface, which was at the base of the Apennines Mountains to the north of the Moon’s equator. PRIME-1’s destination is the Moon’s South Pole – new territory far from all the Apollo landing sites – a location very interesting because NASA has previously detected water there from space. However, gathering more accurate data requires PRIME-1, like ALSD, to land and drill into the surface to examine what is there.

What PRIME-1 discovers will help to update resource models for where explorers are most likely to find water on the Moon. About a year after the PRIME-1 mission, NASA will send an exploratory rover – Volatiles Investigating Polar Exploration Rover, or VIPER – to the surface. VIPER is NASA’s first mobile robotic mission to the Moon, and will carry a TRIDENT drill and scientific instruments that enable it to directly analyze water ice on the surface and subsurface of the Moon at varying depths and temperature conditions. VIPER will explore multiple sites on the lunar South Pole for about 100 days.

PRIME-1 and VIPER will build upon the legacy of Apollo 15 by using drills and rovers, allowing NASA the chance to look below the surface and detect what is there. Much like Apollo 15, NASA is preparing to send new capabilities to the Moon that will enable people to stay there for longer than ever before, because learning how to find and use water is a key to living and working on the Moon and other deep space destinations.

“The Apollo missions first introduced the concept of drilling to provide subsurface understanding of a foreign world,” said Dan Andrews, VIPER Project Manager. “PRIME-1 and VIPER will expand the state of the art as we look to a future of sustainable exploration and learning how to live off the land.”


Maybe NASA needs to hire the world’s best deep-core drillers!

Apollo 15 Crew

Mission Commander (CDR) David R. Scott is 89 years old and lives in San Antonio, Texas. Apollo 15 was his second Apollo mission. He previously flew on Gemini 8 and Apollo 9.

Command Module Pilot (CMP) Alfred M. Worden. Col. Worden passed away last year at the age of 88. Apollo 15 was his only spaceflight mission.

Lunar Module Pilot (LMP) James B. Irwin. Col. Irwin died of a heart attack in 1991 at the age of 61. Apollo 15 was also his only space flight mission.

Apollo 15 Landing Site

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