Paul D. Spudis
The Once and Future Moon
Smithsonian Air & Space

Imagine that you are an astronomer. You want to gaze at the universe in crystal clarity. Yet you look at the heavens through a murky, partly opaque sky; you must deal with light pollution and the dynamic, wildly unstable platform of the Earth’s surface. It’s frustrating – you dream of the great views you know you could get from space. That’s the ticket! Plus, locating a stable, rock-solid base in space (where you could build extremely sensitive instruments) would be a huge bonus.

For years, the Moon was seen as the ideal place to build and operate sensitive telescopes. Its low gravity permits the building of giant telescopes with enormous seeing power. The stable, seismically quiet base of the lunar surface would allow for the operation of multiple telescopes in unison – arrays, effectively creating one giant telescope with an enormous aperture (a technique called interferometry). The cold, dark sky as seen from space – unimpeded by clouds, air or other meteorological phenomena – affords superb viewing conditions (as twenty years of fantastic Hubble Space Telescope images have documented). So with such considerations, one might conclude that conducting astronomy from the lunar surface would be one of the prime activities desired by the astronomical community. Right?

Well, not quite. Back in 1984, efforts to build a community of supporters for a base on the Moon included many astronomers who supported such efforts on the basis of the considerations listed above. Throughout the early days of the return to the Moon movement, astronomers such as Harlan Smith of the University of Texas and many others campaigned tirelessly for recognition of the value of lunar-based astronomy. These studies culminated in the seemingly outrageous idea for a telescope using a spinning disk of liquid with a reflective surface, lining the interior of one of the millions of bowl-shaped craters on the Moon. Such an instrument would extend for kilometers, making a gigantic “eye” to look at the universe. One might think such an idea is crazy, but liquid mirror telescopes already have been constructed on Earth.

Interestingly enough, the launch and success of the Hubble Space Telescope resulted in the loss of support for lunar astronomy. The biggest advantage of space-based astronomy is views of a dark, clear sky. Such views are available in free space just as easily as they are on the Moon. Moreover, the big advantage of a stable platform on the lunar surface for observations is partly negated by technical developments that permit the assembly of free-flying platforms in space. Such developments might mean that a short wavelength interferometer could be built and operated without the need to go into the (small) gravity well of the Moon. These and other technical innovations led to a general loss of support within the community for astronomical science on the lunar surface.

Image of the southern sky in the far UV, taken by the first astronomical telescope on the Moon, Apollo 16 mission, April, 1972 [NASA].

One might be forgiven for suspecting that a long-standing antipathy against human spaceflight might have had something to do with the attitude of many astronomers. They might possibly have feared that the advent of a new human spaceflight endeavor would divert funds from their lengthy wish list of robotic missions and automated observatories. However, the idea that the Moon is somehow useful to astronomers still holds an attraction.

Recent work has focused on the value of using the Moon’s unique environment to observe some parts of the electromagnetic spectrum that we cannot access from Earth or even near-Earth space. Very long wavelength emissions (meter- and multiple-meter-scales) cannot be seen from the Earth’s surface because the layer of charged particles surrounding the Earth in space (the ionosphere) blocks such radiation. Even in orbit, interference from the ionosphere prohibits observations because of this “noise.” However, the far side of the Moon is permanently shielded from Earth’s radio noise by over 3,600 km of solid rock. From such a truly unique vantage point, we will be able to listen to the whisper of radio noise generated in the aftermath of the origin of the universe.

The Chang’E 3 lander carries a small telescope designed to look at the other end of the spectrum, the far ultraviolet (as the name implies, wavelengths shorter than visible light). The Chang’E telescope is producing data and although of small aperture, it can observe the sky at these wavelengths. Apollo 16 emplaced a UV telescope on the Moon back in 1972 and took ultraviolet photographs of the sky from the lunar surface, including the Earth and images of the southern sky (which includes two satellite galaxies to our own Milky Way galaxy – the Magellanic Clouds). These instruments documented the possible value of such observations from the surface of the Moon.

Other astronomers have looked in detail at how one might begin to utilize the unique environment of the far side to map the earliest stages of the history of the universe. One concept sends a teleoperated rover to the far side with a dual purpose. We could collect samples from the floor of the biggest, oldest basin on the Moon (South Pole-Aitken basin, an impact feature over 2,500 km in diameter) to test ideas about the early cratering history of the Earth-Moon system.  While we’re there, we could also lay out an antenna array designed to map the sky’s low frequency radio emissions.

HDTV still of Tsiolkovskiy crater from Japan's lunar orbiter Kaguya (SELENE-1). The Naval Research Laboratory, MIT and others are refining work on a possible radio telescope array deployed on the floor of the conspicuous farside crater to utilize the radio quiet of the lunar farside to probe the Cosmic Dark Age [JAXA/NHK/SELENE].

The far side L-2 mission concept involves humans stationed 60,000 km above the Moon to operate the rovers and deploy the antennas. These antennas are quite simple. They consist of dipoles (i.e., linear wires) several tens of meters in length, all connected to a receiver capable of listening to those low frequency bands minus the static and noise of the terrestrial RF environment. Over the course of a year, as the Moon orbits the Earth (and both orbit the Sun), nearly the entire sky could be mapped from this robotically emplaced astronomical instrument.

Despite some starts and stops, the promise of conducting astronomy from the Moon continues to draw the attention of imaginative scientists. Using one of the forthcoming commercial lunar landers, a group of private enthusiasts plan to deploy a small telescope on the surface. When we some day stand on the Moon, we will not only look down to study the complex history preserved there, but we will also look outward, into an endless universe, just as many science fiction authors envisioned.

Dr. Paul D. Spudis is a senior staff scientist at the Lunar and Planetary Institute in Houston. This column was originally published by Smithsonian Air & Space, and his website can be found at www.spudislunarresources.com. The opinions he expressed here are his own, and these are better informed than most.

Related:
ILOA to study deep space from Chang'e-3 (September 11, 2012)
Remote-operated lunar deep space telescope concept demonstration (July 26, 2012)
Farside offers radio-quiet to probe cosmic Dark Age (July 2, 2012)
The Moon as a platform for Astrophysics (April 24, 2012)
MIT to lead development of new radio telescope
array on lunar farside (February 19, 2008)
Naval Research Laboratory to design Farside DALI (March 11, 2008)
What better view? (March 26, 2008)
New model of lunar motion from Apollo LLRR (December 27, 2008)
MacDonald LLR defunded by NSF (June 21, 2009)
The continued importance of lunar laser ranging (August 3, 2009)
Laser Ranging and the LRO (August 12, 2009)
A Fundamental Point on the Moon (April 13, 2010)

Apollo 17 commander Eugene Cernan (UR, LR), CM pilot Ron Evans (UL, LR) and LM pilot and geologist Harrison "Jack" Schmitt (LL) relaxing in the Apollo 17 Command Module America after Cernan and Schmitt returned from three days of exploring the magnificent Taurus Littrow valley, the last manned expedition to the lunar surface 40 years ago, December 1972 [NASA/ Arizona State University].

Mark Robinson

Principal Investigator

Lunar Reconnaissance Orbiter Camera

Arizona State University

This year, we commemorate the forty-fourth anniversary of the first human lunar landing. By now, the whole world is very familiar with the high-quality Hasselblad snapshots taken by the Apollo astronauts during their voyages. However, 35-mm cameras were also carried on some of the Apollo missions for both surface and orbital imaging. Most of the surface 35-mm images are extreme closeups of the lunar regolith from the Apollo Lunar Surface Closeup Camera (ALSCC; Apollo 11, 12, 14); sometimes called the Gold Camera after its Principal Investigator Thomas Gold.

The Nikon camera used on board the Apollo Command Module was equipped with a 55-mm lens and was loaded with either black-and-white or color film. During Apollo missions 16 and 17, black-and-white film was used for dim-light photography of astronomical phenomena and lunar surface targets illuminated by Earthshine. During Apollo 17, color film was used for documenting various activities in the Command Module.

The 35-mm frames are now scanned as part of a joint project between Arizona State University and the NASA Johnson Space Center to scan all of the original Apollo flight films.

Boot print anaglyph - Stereo anaglyph (get out your red-blue stereo glasses!) AS14-77-10369a,b from the ALSCC showing extreme detail of an astronaut bootprint in the fine-grained lunar regolith. The original field of view is about 3 inches on a side [NASA/Arizona State University].

The Apollo 17 crew seems to have had the most fun with the 35-mm format! Gene Cernan, Ron Evans and Jack Schmitt snapped quite a few spectacular black-and-white images showing the view out of the window of their Command Module, the America. Some of these images are a bit grainy, resulting in a very different feeling than the crisp Hasselblad photographs. They also took numerous color candid shots inside the Command Module. It is rare to see such carefree moments during the Apollo missions, but you can feel the relief and happiness after the astronauts so successfully fulfilled their surface mission!

Reiner Gamma illuminated solely by earthshine (35-mm Apollo 17) - Reiner Gamma, one of the enigmatic lunar swirls; their origin is related to localized magnetic fields within the crust AS17-158-23894 [NASA/Arizona State University].

Many of the window shots present an oblique view across lesser known regions of the Moon. The terminator (boundary between night and day) scenes are always captivating. Look closely at the scene below; near the center is a shallow-sloped scallop-shaped rise. Just below and to the right are two other smaller rises - perhaps these are low shield volcanoes? You can dig deeper by visiting the LROC QuickMap browser and see if the NAC images can elucidate what is seen here (Natasha crater is at 19.973°N, 328.843°E).

Mare Imbrium meets Mare Procellarum (Apollo 17 35-mm frame) a complex region composed of nearly buried peaks that are part of the Imbrium rim, impact craters, and volcanic forms. Annotated AS17-160-23992 [NASA/Arizona State University].

Relive the incredible adventure that was Apollo, browse the Apollo 35-mm archive and the rest of the Apollo scans (Metric, Pans; Hasselblads to follow next year). While browsing, map out your own next mission to the Moon! The hard part is figuring out where to visit next. Enjoy!

Related Posts:
Project Mercury Photography Now Online
Project Gemini Comes to Life
Reiner Gamma Constellation Region of Interest
Mare Ingenii Swirls

In the days before his first mission into space, way back in March 1965, John Young was asked by a journalist if he minded flying into orbit with the fiery Virgil ‘Gus’ Grissom as his Gemini 3 crewmate. Without blinking, the 34-year-old Young replied: “Are you kidding? I’d go with my mother-in-law!” It was an indicator not only of Young’s intense dry wit, but of his equally intense devotion to the exploration of the final frontier – an exploration which consumes 400 pages in his long-awaited memoir, Forever Young, co-authored with Auburn University history professor and Neil Armstrong biographer James R. Hansen.

Long-awaited because Young has earned himself a reputation over the past five decades which cannot be surpassed. True, there are astronauts who have flown more times into space than him. True, there are other astronauts who have walked on the Moon, besides him. True, there are astronauts who have commanded more missions and flown longer in space than him. But for sheer longevity within the astronaut business, John Watts Young is unrivaled. Selected as a member of NASA’s second intake of spacefarers in September 1962 – an intake which former chief astronaut Deke Slayton once described as “probably the best all-around group ever put together” – he spent more than 40 years with NASA and flew six times, across three separate programs: Gemini, Apollo and the Shuttle. Even Jerry Ross, who became the first human to record a seventh voyage into space, has described Young as his hero.

Read the full review at AmericaSpace, HERE.

Apollo 11 capcom and Apollo 16 lunar module pilot Charlie Duke addresses Monte Sano Methodist Church in Alabama, July 22, 2012. Congregants snacked on Moon Pies and Tang before heading into the sanctuary to commemorate Buzz Aldrin's "lunar communion" 43 years ago, Friday [Glenn Baeske/The Huntsville Times].

Steve Doyle
The Huntsville Times
 
"It seemed only appropriate that astronaut Charlie Duke - the 10th human to set foot on the moon - was the guest of honor at the church's "Lunar Communion" service Sunday morning.

Pastor Dale Clem said Monte Sano United Methodist is one of just two U.S. churches that commemorate astronaut Buzz Aldrin taking communion on the moon July 20, 1969 - 43 years ago Friday. Aldrin's church, Webster Presbyterian in Houston, is the other.Before heading into the sanctuary, worshipers snacked on Moon Pies, crescent-shaped cantaloupe slices and, of course, Tang.

Selected for the astronaut program in 1966, Duke was in mission control as Aldrin and Neil Armstrong delicately maneuvered their Apollo 11 lunar landing module toward the moon's surface.

"Roger, copy you down, Eagle...We're breathing again." As Apollo 11 capcom, Duke was first to talk directly with another on the Moon [NASA].

Duke, the lunar landing module pilot, said his heart was racing at 144 beats per minute as the Saturn V took to the heavens. Commander John Young, making his second space voyage, was a relaxed 70 beats per minute.

When Duke's heart finally stopped hammering, wonder took over. He said he'll never forget the first time he gazed back toward home from 20,000 miles away.

"That jewel of Earth - the browns of the land and the crystal blue of the oceans and the pure white of the snow and clouds - is indelibly imprinted upon my mind."

Duke said he didn't have a spiritual experience, per se, during the 20 hours he spent combing the moon's surface.

But after returning to a hero's welcome and diving back into the business world, he said he began longing for something more.

Duke said he found what he was looking for when he reluctantly agreed to attend a three-day Bible study at a tennis club in New Braunfels, Texas.

Joel Raupe

Lunar Pioneer
 

A boulder that seems precariously balanced on the rim of 4.3 kilometer crater Descartes C (11.028°S, 16.273°E) was photographed by the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC), last year, as LRO happened to be maneuvering through a cycle of exceptionally low orbital passes. It was a fortunate happenstance for Larry F. Scott and myself, because we once suggested a spot only a few meters away for a notional unmanned landing target. Though our area of interest in 2008, the Descartes Formation, so far, appears only sporadically in the released LROC NAC catalog, the team at Arizona State, headed by Mark Robinson, could not have picked a better target for us when LRO was "skimming the Moon," last year.

In 2011, after maintaining the LRO primarily in a low,  near-circular polar orbit, between 35 and 65 km high, for nearly three years flight directors began a change-over to their preferred method for extending the record-breaking mission into 2015, to raise LRO's orbit above 100 kilometers, which they accomplished very early in January.

Their plan reduces, but does not eliminate, the demands on LRO's limited supply of propellant needed to maintain a minimally useful near-circular polar orbit. (See, "Skimming the Moon," September 6 2011.)

The Moon is anisotropic, or "lumpy," as Dr. Robinson reminded us, and its notorious mascons and mass-voids put an uneven drag on LRO's baseline altitude, and this requires well-planned periodic maneuvers to prevent the vehicle from crashing after only seventy days or so. But before raising LRO's orbit, twice in 2011 the spacecraft was maneuvered through brief periods when the low point in its orbit brought the spacecraft down to within 25 kilometers from the surface, and this allowed for some really spectacular and detailed surveys, including even more extraordinarily detailed examinations of the Apollo landing sites.

These close passes also presented opportunities to gather other NAC observations to within 40 cm per pixel, and among the smaller NAC footprints delivered up in March was a nearly complete cross section of Descartes C, a typical small crater situated in a familiar, though unusual, location in the Southern Highlands.

Fig. 3. At full resolution, a 550 km field of view marked off with by a yellow rectangle in Fig. 1, up above, directly centered on the bright Descartes albedo 'swirl;' viewed through a better-than-average telescope. Slightly above and to the left (northwest) of the swirl both North and South Ray craters can be seen, making the Apollo 16 landing site one of the easiest to "pick out" with the mind's eye, even with a telescope back on Earth. Again, the really breathtaking full mosaic by Yuri Goryachko, Mikhail Abgarian & Konstantin Morozov of Belarus, can be viewed HERE. [Astronominsk].

Descartes C marks one indefinite extent of the Descartes formation, a small field of furrows and segmented hills stretching to the crater's northwest, topped with a distinct and bright, but small and amorphous "swirl" resembling a fresh snowfall. This 400 sq. km. patch of optically immature surface, nested inside a remarkably intense local magnetic field, rates higher than average scientific interest.

Our 2008 proposal included a teleoperated robotic ground survey beginning at Descartes C, lengthwise, through the heart of the unusual terrain and swirl, and its lunar magnetic anomaly, perhaps eventually emerging near the landing site of Apollo 16. Today we have an additional stop on that 'fantasy tour' a short distance from our originally proposed landing site. 

Fig. 4. LROC QuickMap (250 meter resolution) view, also centered on the 'anomalous' albedo and the Descartes Formation, seen here mixed with the false color of the LROC Wide Angle Camera (WAC)-derived topography. Again, a yellow rectangle marks off the field of view visible in Fig. 7, below. Note the "centipede" chain of half-kilometer long hills, training to the northeast from Descartes C. That feature is the most obvious distinction setting the formation apart from nearly every other spot on the Moon's surface. The age and wear of Descartes crater becomes more obvious as one closes in on the area [NASA/GSFC/DLR/Arizona State University].

Fig. 5. Simulated slightly oblique view over Descartes (29 km), from the Cayley Formation plains explored by Apollo 16 in the northwest, 80-plus kms southeast over the Descartes Formation and its swirl albedo to the highly-eroded main Descartes crater in the south. LROC WAC mosaic, from observations collected in three sequential orbital passes December 3, 2011, averaging 52 meters resolution, from 38 km, 70° angle of incidence [NASA/GSFC/Arizona State University].

Fig. 6. "Figure 2" from "Correlation of a strong lunar magnetic anomaly with a high-albedo region of the Descartes mountains," by Richmond, Hood & Halekas, et al. (GFL, V. 30, # 7, 2003) "Contour map of the two-dimensionally filtered magnetic field magnitude (in nano-Teslas, or nT) at an altitude of 18.6 km in the vicinity of the Apollo 16 landing site (boxed cross). The photo- graph is a portion of Apollo 16 mapping camera frame 0161 (AS16-M-0161). Several exposures of the Cayley formation (CF) and the adjacent Descartes mountains (DM) are indicated" [Lunar Prospector Magnetometer data, 1999].

Our paper broadly outlined a very notional multipurpose robotic lander-rover mission in support of the proposed International Lunar Network (ILN). We advocated discovery of ground truth about one lunar magnetic anomaly in particular, and its well-known relationship with a bright surface swirl marking. Also, we wanted to add our small voices to the chorus recommending a cautious approach to the scientifically valuable (and remarkably fragile) artifacts of Apollo, "from the ground, and from a distance." Of course, since then, a growing chorus has out-grown much need for small voices. The NASA Human Exploration and Operations Directorate's recommendation "to space-faring entities," released in July 2011 explicitly spells out the agency's similar concern.

Interest in lunar swirl "patterns" appears as strong as ever, and may be growing. It's become difficult to remember that little more than a decade ago the anomalous albedo 'swirls' today associated with features near Descartes and nearby Airy craters (both easily visible from Earth) were still little recognized.

Because the more famous, more aesthetically pleasing swirl fields at Reiner Gamma, Mare Ingenii and Mare Marginis have been properly associated with local crustal magnetism the recognition of anomalous optically immature regolith elsewhere on the Moon was "reverse engineered."

In the case of smaller 'smudges' near both Airy and Descartes craters, for example, acknowledgement as true swirls has depended on the fleeting detection of magnetic fields at both locations late in the Lunar Prospector mission, not long prior to its eventual crash landing in Shoemaker crater, near the Moon's south pole, in 1999.

For many years after the demise of that small spacecraft researchers continued to tease more and more data from a telemetry stream that today seems remarkably sparse when compared with oceans of data continuously relayed back from LRO. Magnetometer readings from only two low altitude fly-over encounters by Lunar Prospector with the Descartes Formation delivered sufficient evidence to demonstrate a tightly wound mini-magnetosphere existed over the bright albedo swirl, upon on the unusual hills between Descartes crater and the landing site of Apollo 16. The relatively small magnetic anomaly may be the most intense crustal magnetism on the Moon (See Fig. 6).

Fig. 7. The swirl painted on the unique contours of the Descartes formation, just beyond the eroded northern rim of the main crater, is not as striking a in photographs taken from orbit, such as the picture taken from Apollo 14 and 16, or the LROC Wide Angle Camera images from close orbit. The estimated strength of the very localized magnetic field, as measured from Lunar Prospector from an altitude of 18.3 km in 1999, is indicated in nano-Teslas (nT).  LROC WAC observation M177535094C (604nm), LRO orbit 11299, December 3, 2011; angle of incidence 69.57° at 52.3 meters resolution from 38.27 km [NASA/GSFC/Arizona State University].

It's difficult to recall any controversy over the origin (and natural sustaining) of optically immature regolith, at Reiner Gamma, for example. Nevertheless, some very respectable researchers still insist the swirl albedo patterns are the result of scant, recent encounters with comets. The most detailed crater counting methods have all but ruled out any swarming impact origin to the Reiner Gamma swirl. The magnetic field strengths associated with many of these fields are, in some cases (e.g., Descartes and Gerasimovich), sufficiently intense to refract solar wind, but these fields are too small in scale to refract their less frequent but cumulative encounters with the most energetic and heaviest cosmic radiation.

Remote sensing of the Descartes swirl indicates the presence, in abundance, of nanophase iron in the surface grains, thought to be at least one of the ingredients of optical maturity, and a strong indicator of the transparency of the local magnetic field to iron nucleons, a big part of the cosmic ray mix. (Unless, of course, lunar micro-grains implanted with nanophase iron arrived at the site by another mechanism.)

Swirl fields and their associated magnetic fields along the north rim of 4 billion year-old South Pole-Aitken basin are each individually, very closely associated with the antipodes of the most easily-recognized nearside impact basins. The lovely swirls of Mare Ingenii, for example, are nearly on the direct opposite side of the Moon from Mare Imbrium, and the jumble of swirls in and around Goddard crater and Mare Marginis are similarly on the opposite side of the Moon from Mare Orientale.

Because these basins are still believed to be between 3.85 and 3.1 billion years old, respectively, the ages of the magnetic fields clustered at their antipodal foci are thought to be at least as old as those impacts. (But, it should be noted here that no basin-forming impact has yet been associated with the antipodes of smaller nearside swirl patches near Airy or Descartes craters, nor, for that matter, with the unique and much more widespread Reiner Gamma swirl within Oceanus Procellarum.)

The persistent mystery of lunar swirl patterns is still the longevity of "optical immaturity," brightness at the lunar surface that constitutes the swirls themselves. As soon as these "patterns" were associated with local crustal magnetism it was quickly suggested that some refraction, even reversal, of the relentless solar wind kept the surface under their influence from being "darkened." Experiments with high-energy radiation bombardment under laboratory conditions, the energetic variety of cosmic rays that can't be steered away by these fields, appears to indicate that, eventually, any lunar regolith will mature, after only 900 million years or so. As the upper few centimeters of the lunar surface is eventually pulverized into abrasive powder, the process of maturation by hard radiation gets underway.

So how is the optically immature regolith of these swirls kept fresh?

It was our suggestion in 2008 that the answer rests in the very slow migration of lunar dust. The supply of fresh, optically immature dust is continuously supplied by the gardening of impacts, both large and very, very small. And then, at the beginning and end of a daily cycle of charging and discharging of these smallest grains, these nested magnetic fields (which are likely to have more than one kind of origin) preferentially lose and accumulate both mature and immature dust, dividing up both the levitation and fallout along opposing polarities, in a very slow process that still manages to out pace the relentless process of "reddening" or "darkening" by hard radiation, admittedly a less frequent kind of radiation than the bulk of solar wind, but just as relentless.

Which brings us to "Boulder 668," on the north rim of Descartes C, a crater that is itself nested on the north rim of a far more ancient crater, Descartes. The number "668," by the way, marks the boulder's elevation, according to a rough reading of the LROC QuickMap website and its WAC-derived digital elevation model. Obviously there's nothing official about the name.

The boulder reminds us of "House Rock," as well, its smaller cousin ejected out from the North Ray crater impact, and at one time closely examined and sampled directly by John Young and Charles Duke in 1972 (and only about 80 km away from Boulder 668 and Descartes C).

Charlie Duke samples a shatter cone formation in Outhouse Rock, a large fragment shed off the southern end of House Rock, at North Ray crater during the third and final EVA of Apollo 16.  AS16-116-18649 [John Young/NASA/JSC/ALSJ].

The choice for the Apollo 16 landing site, the only manned visit to the lunar highlands, and a landing site referred to as "Descartes," was made in the sincere belief that the apparently unique topography of the Descartes Formation strongly indicated the area to be volcanic in origin. Mission planners were disappointed to discover, almost immediately after Apollo 16 landed, however, no obvious sign of volcanism.

On their second EVA, Young and Duke drove up the slopes of "Stone Mountain," the northwest extreme of the Formation, and looked high and low for a sample uncontaminated by ejecta from nearby South Ray crater.

On their departure from the Moon Captain Young remarked about "still mysterious Descartes," unaware then of the tantalizing evidence they had almost inadvertently uncovered. Their haul of samples proved every bit as valuable as any from the Apollo missions to the overall body of lunar research in the decades following Apollo.

Almost as a footnote, their magnetometer readings proved to be the strongest ever detected on the lunar surface.

In the years since Apollo it's become generally accepted that the unique topography of the Descartes Formation, completely apart from its swirl albedo and magnetic personality, "probably" originated with the impact that formed Mare Imbrium, whose influence is so clearly etched into the landscape of the region, so obviously radiant from the center of that basin. Others say the Nectaris impact, before Imbrium and closer by, tossed up what may turn out to have been a very large, semi-coagulated chuck of impact melt that quickly fell back to the Moon more or less intact, immediately settling in and around existing crater remnants.

Also generally recognized as perhaps the oldest, remarkably intact feature of area is old Descartes itself, an apparently very worn and "tortured" crater differs in many ways from worn craters of apparently the same age elsewhere on the Moon. As worn as it is, it's concentric rings have, for the most part, not been erased (again, remarkably) appear more like a sand castle after the first wave of an incoming tide, without the notched rims characteristic of many largely intact older craters. Descartes seems over washed, with an infill of material around it which consists of more than just the convoluted terrain of the Descartes Formation plateau to its north.

In any case, Descartes, by all appearances, hollowed out a place in the ancient Southern Highlands, perhaps prior the supposed late heavy bombardment.

Though Descartes is now mostly "back-filled," today, more likely from a steady bombardment that erased many of its nearby contemporaries, the impact that formed the old crater tossed up its deepest excavated material and deposited this around its smoothed rim. Some time after this, apparently not from volcanic vent, the half-kilometer-scale chains of hills and furrows of the Descartes Formation arrived on the crater's north exterior, forming or deforming a plateau. Under that material, or, more likely, within the material itself is a very intense, very local crustal magnetic field. That field has since interacted with the slow process of lunar dust charging, discharging, preferential accumulation and levitation, dust migration and the forces driving optical maturity, to form the bright swirl within the magnetism's exceptionally strong influence.

Eons pass, and along came the progenitor that excavated Descartes C crater at the crossroads of all this ancient history. In its formation there was tossed up along its rim the long-buried material once tossed up from an even greater depth by Descartes. "Boulder 668" may represent a bulk of older material less shock metamorphosed than the melt splashed over its rim and pooled on its small floor. The boulder poses questions more, perhaps, than it answers.

In 2008 we fancifully suggested approaching the artifacts of Apollo 16 from the ground, and from a distance of 80 kilometers, all starting with a landing less than 100 meters from the north edge of Descartes C and "Boulder 668." Showing great faith in the future of robust teleoperated robotics we suggested being driven to reconnoiter the Descartes Formation to closely examine "still mysterious Descartes," its magnetic field and albedo. Now, thanks to this remarkably close examination of our proposed landing site we have our fantasy rover's first stop picked out for us for us to examine, and a reason to linger around the perimeter of Descartes and Descartes C a little longer than originally planned.

Fig. 8. Descartes C (4.32 kilometers, centered near 11.028°S, 16.273°E), nested on the deeply eroded rim of Descartes proper, has gradually been seen in increasing detail following multiple LROC Narrow Angle Camera (NAC) observations over LRO's three years in lunar orbit. No longer just a bright crater in a bright region, having excavated an unusually complex area, Descartes C is itself richly complex, with impact melt on steep walls and debris flows into a small kilometer-wide melt-flooded floor. The boulder at 668 meters elevation, high on its rim, was excavated from below the melt pond 750 meters below [NASA/GSFC/Arizona State University]

Mark Robinson

Principal Investigator
Lunar Reconnaissance Orbiter Camera
Arizona State University

On May 28 LRO was slewed 59° to the west, from an altitude of 92 km (57 miles) and captured a dramatic view of the Apollo 16 landing site.

During the Apollo 16 mission Ken Mattingly passed over the site several times at an altitude of 120 km (75 miles).  If you imagine yourself in the Command Module, then this view is close to what you would have seen.

The lighting is nearly identical to that of when the Lunar Module Orion set down on the Moon.

On the second day of surface activities John Young and Charlie Duke headed south to sample material from Stone mountain and ejecta from South Ray crater. They headed south and turned east climbing up the flank of Stone Mountain. Imagine the view that Young and Duke had from Cinco crater (Station 4)! From their vantage point some 300 meters above the LM, the astronauts could see all the way from South Ray crater to North Ray crater.

With the annotated version you can easily retrace the routes followed by Young and Duke as they spent three days exploring this highland landing site. Read a detailed reconstruction of the astronaut activities through the Apollo Lunar Surface Journal. 

What did they find at House Rock? Why was Shadow Rock an important science target? Is Baby Ray crater older or younger than South Ray crater? Then imagine yourself picking up where the Apollo astronauts left off over forty years ago!

When will we return to the Moon?

Dive into the full resolution oblique shot of the Apollo 16 site, HERE.

Retrace the astronaut traverses in an annotated version of oblique image, HERE.

Previous Apollo 16 LROC Featured Images

Orion, Up Close

Footsteps Under High Sun

Fly over the Apollo 16 landing site and follow the journey
of Young and Duke to North Ray crater and back:  

40 years parked on the Cayley plain northwest of the Descartes formation.

The Apollo 16 Lunar Module Orion set down on the lunar surface 40 years ago (21 April 1972) after remaining in a holding pattern for six hours while technical issues with the Command Module Casper were resolved.

Here John Young and Charlie Duke undertook the first and only exploration of a highlands site; their main goal was to sample the enigmatic light plains deposits that geologists had interpreted as remnants of a large scale explosive volcanic eruption.

These proposed volcanic rocks were to be very different than the volcanic mare basalts sampled at previous sites (Apollo missions 11, 12, and 15).

Once Young and Duke started looking at rocks near Orion, it became clear that there were no strange highland volcanic rocks. What they found were breccias, breccias, and more breccias. Why breccias, and how did they form? The Apollo 16 rocks were most similar to those collected by Apollo 14 astronauts Al Shepard and Ed Mitchell. As it turns out, the breccias formed as part of massive flows of ejecta from the Imbrium and Nectaris basin-forming events. Young and Duke were sampling crushed rocks that flowed hundreds of kilometers from their source!

Similar to the other Apollo missions, the Apollo 16 crew set up science instruments to measure varied aspects of the Moon and its environment. Most science instruments were part of the Apollo Lunar Surface Experiments Package, or ALSEP. The Apollo 16 crew also carried with them on their geology traverses the Lunar Portable Magnetometer (LPM) that measured variations in the strength of the Moon's weak magnetic field. Some of the ALSEPs (Apollo missions 12, 15, 16) carried a stationary Lunar Surface Magnetometer (LSM) that provided a point measurement for the landing site as a whole.

The LSMs showed that from site-to-site the magnetic field varied by about a factor of fifty, from a low of 6 gammas (Apollo 15) to a high of 313 gammas (Apollo 16). From the LPM station-to-station measurements within the Apollo 16 traverses, the magnetic low was 121 gammas and high the high was 313 gammas; a factor of nearly three over a distance of 7 km.

After setting up the LPM, a final experiment was performed by measuring the magnetic field before and while a small rock was perched on the experiment. This experiment returned two important results: a) the local rocks had a remnant magnetic field so weak that the LPM could not detect it, and b) that the LPM was still working as before launch. These results came from the fact that the astronauts brought the sample (60335) back to Earth, and it was measured by an identical LPM as well as well as even more sensitive instruments.

What did these varied magnetic readings tell us about the Moon? The Moon's magnetic field comes from crustal and mantle materials, has no dipole signature, and is very weak. 

This is a magnetic field very different from the dipole field generated in the Earth's core. Right now scientists do not understand the origin of the lunar magnetic field or its variations. Perhaps the signature of an early, but now extinct, dipole field was captured in ancient lunar rocks as they cooled from a magma ocean. 

Perhaps basin-forming impacts induced local fields in the crust. These Apollo area measurements do tell us that the interior of the Moon is heterogeneous and complicated: the Moon is not a simple body. The two GRAIL spacecraft, Ebb and Flow, that are now in orbit about the Moon will provide gravity measurements that geophysicists will use to deepen our understanding of the lunar interior; the Apollo era magnetic readings will be part of that unfolding story.

Trent Faris
WBTV Charlotte

LANCASTER, SC (WBTV) - Most kids grow up dreaming of the stars wanting to be an astronaut.

When Charlie Duke was at Lancaster High School in 1950 he just dreamed of following his father's footsteps to be a military officer. After graduating from the Naval Academy, Duke became a pilot in the Air Force.  He was serving as a fighter pilot in Germany when he heard about the first selection of astronauts to go into space.

"I began to say man that ought to be a fun, fun experience, but I wasn't qualified. Then I thought the space program would pass me by," said Duke during a rare sit-down interview with WBTV.


Duke ended up at MIT where his work on Apollo guidance and navigation systems earned him a ticket onto the Apollo program. In the nine Apollo missions to go to the moon, Duke worked on five of them, including Apollo 11.

"Well, Neil Armstrong came to me and said 'How about doing the same thing you did on 10 for us' so I developed those procedures," said Duke.

Everyone knows these famous words: "Houston, Tranquility base here. The Eagle has landed." Those words came from Armstrong after the first successful landing on the lunar surface in 1969. 

The voice you hear next on the transmission from mission control - was Duke. "Roger that Tranquility. We copy you on ground. You've got a bunch of guys about to turn blue, we're breathing again," Duke was recorded saying.

Duke was the back-up Lunar module pilot for Apollo 13 and 17, but Apollo 16 was his mission to the moon.

Read the article, HERE.

From the Apollo Lunar Surface Journal: 120:25:42 "John Young jumps off the ground and salutes for this superb tourist picture. He is off the ground about 1.45 seconds which, in the lunar gravity field, means that he launched himself at a velocity of about 1.17 m/s and reached a maximum height of 0.42 m. Although the suit and backpack weigh as much as he does, his total weight is only about 65 pounds (30 kg) and, to get this height, he only had to bend his knees slightly and then push up with his legs. In the background, we can see the UV astronomy camera, the flag, the LM, the Rover with the TV camera watching John, and Stone Mountain. Journal Contributor Joe Cannaday notes that high-point of John's first jump was at a time close to 120:25:49 and the second was almost exactly three seconds later."

After trading places for Young to capture Duke's 'Air Force salute' Houston passes along 'good news.' The U.S. House of Representatives has authorized the Space Shuttle program. 

Young, who will command the first Space Shuttle mission 9 years later, answers, "Beautiful. Wonderful. The country needs that Shuttle mighty bad. You'll see."

From the Apollo Lunar Surface Journal: "John became the Chief of the Astronaut Office in 1975 and, later, appointed himself to command the first Shuttle flight. STS-1 was 36-orbit mission launched on April 12, 1981, the twentieth anniversary of Yuri Gagarin's Vostok flight. The pilot - and only other crewmember - on STS-1 was Robert Crippen.".

Landing site of Apollo 16, between North Ray and South Ray craters, northwest of the Descartes Formation ("Stone Mountain, at lower right) in the nearside lunar highlands. Full 52 meter resolution detail from LROC Wide Angle Camera monochrome (604nm) observation M177535094C, LRO orbit 11299, December 3, 2011; angle of incidence 69.4° from 38.2 kilometers altitude [NASA/GSFC/Arizona State University].