Apol­lo 17: Des­ti­na­tion Tau­rus-Lit­trow - 6th and fi­nal Lu­nar Land­ing

Jack Schmitt examines Tracy's Rock
Jack Schmitt ex­am­ines Tra­cy's Rock
Image 1/4, Credit: NASA

Jack Schmitt examines Tracy's Rock

Jack Schmitt in his el­e­ment as a field ge­ol­o­gist. For over an hour the as­tro­nauts stud­ied an 18 me­tre-long rock that had rolled down a hill­side out­side the im­age and in­to the val­ley. Gene Cer­nan ac­tu­al­ly want­ed to write his daugh­ter’s name in the dust on the rock, but for­got to do so, so the rock now bears her name in­stead.
Orange lunar soil
Or­ange lu­nar soil
Image 2/4, Credit: NASA

Orange lunar soil

“It’s all over!! Or­ange!! … I stirred it up with my feet.” Jack Schmitt’s ex­cit­ed ex­cla­ma­tion got Hous­ton all fired up, as he and the ge­ol­o­gists be­lieved that they had found very re­cent vol­canic de­posits. How­ev­er, these turned out to be ti­ta­ni­um-rich vol­canic glass that had been sprayed over the sur­face in fiery foun­tains dur­ing vol­canic erup­tions. As the la­va cooled by sev­er­al hun­dred de­grees in no time at all, it did not form a crys­tal struc­ture, so the molten ma­te­ri­al so­lid­i­fied in­to glass. This hap­pened bil­lions of years ago.
Necessity is the mother of invention on the Moon, too
Ne­ces­si­ty is the moth­er of in­ven­tion on the Moon, too
Image 3/4, Credit: NASA

Necessity is the mother of invention on the Moon, too

The lu­nar map had to be used to re­place a dam­aged fend­er on the Rover. With­out this pro­tec­tion, the tyres would have kicked up so much dust that it would have been dif­fi­cult for the as­tro­nauts to drive. The dust be­came lodged in their space­suits and stuck there as though it were glued on.
Apollo 17 Commander Eugene Cernan steering the two-seater lunar rover
Apol­lo 17 Com­man­der Eu­gene Cer­nan steer­ing the two-seater lu­nar rover
Image 4/4, Credit: NASA

Apollo 17 Commander Eugene Cernan steering the two-seater lunar rover

Dur­ing the last three Moon land­ings, the as­tro­nauts were able to ex­plore the ar­eas around their land­ing sites with a lu­nar rover, which was a bat­tery-pow­ered ve­hi­cle with a mass of 210 kilo­grams. The du­ra­tion of their stays on the Moon was ex­tend­ed to three Earth days, al­low­ing three long ex­cur­sions - each cov­er­ing a dis­tance of ap­prox­i­mate­ly 30 to 35 kilo­me­tres - to be car­ried out dur­ing the Apol­lo 15, 16 and 17 mis­sions. This greater mo­bil­i­ty al­lowed the as­tro­nauts to con­duct far more in­ten­sive stud­ies of the lu­nar land­scape and col­lect many more rock sam­ples.

Crew and spacecraft

The era of the Apollo project was drawing to a close. Ever since 1970, it had been clear that Apollo 17 would be the last mission to the Moon in December 1972. For NASA had long since abandoned its plan for the originally envisaged missions 18, 19 and 20, one reason being the expense, another the fact that the program no longer had political backing. Thus, it was a foregone conclusion that no human being would step on the Moon for a long time after Apollo 17.

This was one of the facts that guided the selection of the crew members. Initially, NASA followed the rotation that had been practiced so far, according to which it would be the turn of the backup crew of the second-but-last mission, Apollo 14. This meant that Eugene ‘Gene’ Cernan would definitely be Commander. So Cernan would get to put his foot down in the lunar dust after all, having approached the Moon to within 14,5 kilometers together with Tom Stafford during Apollo 10, the final dress rehearsal for the first lunar landing. Cernan (Apollo 10 and 17), Young (Apollo 10 and 16), and James Lovell (Apollo 8 and 13) were the only astronauts to fly to the Moon twice. Ronald Evans was assigned Command Module Pilot; it was his only space flight. Joe Engle, the Lunar Module Pilot on the backup crew of Apollo 14, should have been the third man on the team. However, NASA allowed itself to be convinced that the last journey to the Moon should be made in the company of a scientist – Harrison ‘Jack’ Schmitt, a geologist qualified by his work during the preparations for Apollo 14, 15 and 16 when he occupied the interface between the mission management and the scientists.

Choosing the last landing site on the Moon proved a difficult job. The list of locations that were proposed and rejected is long indeed. Thus, for example, landing on the edge of Tycho or Copernicus, two comparatively young craters, was taken into consideration – a maneuver which NASA found too risky in the end, just like Schmitt‘s proposal to land on the far side of the Moon for the first and only time. In the end, the researchers agreed with NASA on the Taurus-Littrow valley on the eastern edge of Mare Serenitatis.

On the evening of December 6, 1972, a Saturn V rocket bearing the serial number SA-512 was ready for the last journey to the Moon, its third stage carrying the Apollo spacecraft which, weighing almost 47 tons consisted of the command module ‘America’ and the service module at the top and the lunar module ‘Challenger’ in the third rocket stage.

Mission progress

For the first time, NASA ventured to launch an Apollo mission during the night. The spectacular lift-off into the nocturnal sky above Florida took place on December 7 at 0:33 local time. About half a million people witnessed the historic event, when Apollo unfolded all its fascination for the last time as the 111-meter-high Saturn V rocket launched to the skies.

The further course of the mission was almost perfect. The transfer to the Moon proceeded without incident, followed by Cernan’s and Schmitt‘s picture-book descent to the lunar surface on December 11. Similar to Apollo 15, the last part of the landing maneuver was not uncritical, for ‘Challenger’ had to pass between mountains several thousand meters high, the ‘South Massif’ and the ‘North Massif’ in the mountainous rim of the Serenitatis impact basin.

At 20:54 CET, Cernan touched down the lunar module almost exactly in the spot originally envisaged. “This is absolutely incredible!” Schmitt exclaimed spontaneously, and Cernan described a conspicuously structured mountain slope by saying, “This looks like the wrinkled skin of a man a hundred years old – my God, it‘s beautiful here!” This first inspection of the surroundings through the windows of ‘Challenger’ sent the expectations of the scientists on Earth soaring. No more than four hours after landing, the two astronauts were ready for their first excursion.

Cernan and Schmitt formed a brilliant team; that much had been clear for a long time. Like the two preceding ‘J-missions’ involving a three-day stay, Apollo 17 also carried a lunar rover to increase the astronauts’ radius of action. While the rover was made ready, Cernan’s geologist’s hammer got caught in the fender of the right-hand rear wheel, breaking off part of it. Driving without a fender is disagreeable because the wheels throw up lunar dust which then spreads over the entire vehicle – and the astronauts. To repair the damage, Cernan and Schmitt fixed a geologic map as a spare fender, and the problem was solved.

The astronauts began by installing the geophysical experiments whose design was somewhat different from that of the previous missions: measurements of local gravity fields, which vary because of differences in the composition of the subsoil, proved particularly successful. They furnished geologists with clues to the volcanic past of the area.

On the Moon

Problems occurred only with an experiment that served to detect gravity waves from the depths of space. Researchers would have certainly won a Nobel Prize if they had succeeded in measuring these ‘echoes’ of the Big Bang, the birth of the universe, in the form of seismic vibrations simultaneously on the Earth and the Moon. However, the design of the instrument was faulty, and Schmitt did not succeed in getting it to work well enough to permit meaningful measurements.

On the other hand, they did not encounter any problems placing several small explosive charges along their excursion routes. After their return lift-off from the lunar surface, these charges were fired and the speed and direction of the propagation of the seismic waves measured and radioed directly to Earth. These data could be used to generate profiles of the region’s geologic structure.

At long last, they succeeded in extracting from the lunar soil or regolith a sample two and a half meters in length which, when analyzed later on in a laboratory on Earth, proved conclusively that even the lunar subsoil is literally as dry as dust and does not contain any moisture at all (it was only some 40 years later that researchers were able to show that, because of external influences, water does exist on the Moon, albeit in extremely small quantities of ice).
Another core 2.80 meters in length was used to measure temporal variations in the impact of cosmic radiation neutrons on the Moon. It was found that, because there is no protective magnetic field, the lunar subsoil constitutes an excellent ‘archive’ of the cosmic radiation environment, which is unlike anything we have on Earth.

The greatest significance, however, was attached to the geologic observations made by the two astronauts during three excursions that totaled 22 hours in length. During that time, they took 2200 photos with their Swedish Hasselblad cameras equipped with lenses made by Zeiss in Oberkochen (the manufactory is located not far from Speyer) and gathered 110.4 kilograms of lunar rock. Traversing a total of 36 kilometers in the lunar rover, they went up to 7.6 kilometers away from the lunar module, a distance from ‘Challenger’ which they would have had to cover on foot had the rover failed.

After a somewhat subdued first day, when Jack Schmitt‘s mood was not of the best because not enough good solid geology was being done in his opinion, the excursions of the two subsequent days proved to be the scientifically most productive in the entire Apollo program.

Results

The purpose of Apollo 17 was to find answers to two important questions about the history and evolution of the Moon. First, the landing site at Taurus-Littrow is far enough away from the Mare Imbrium basin which was created by the impact of an asteroid 3.8 billion years ago when the ejecta were scattered across a large part of the near side of the Moon. Selecting a landing site at the rim of Mare Serenitatis, which is markedly older than that of Mare Imbrium, being investigated by Apollo 14 and 15, presented a last chance of obtaining extremely old rock samples. In actual fact, the astronauts succeeded in finding a sample that was more than 4.3 billion years old. At the same time, second, geologists were hoping to find young volcanic rock in the same place, which would have helped to constrain more closely the period during which volcanic eruptions happened on the Moon.

Photos taken by Apollo 15 when in orbit around the Moon show dark areas in the Taurus-Littrow region that appear to be considerably younger than the vicinity. When Cernan and Schmitt went there in their rover, they discovered that these areas actually did consist of volcanic deposits which, however, were far more than three billion years old; consequently, they were no help in answering the second question of how long volcanism was present on the Moon. However, the crew did find unusual volcanic deposits, orange-colored lunar dust created by jets of fire in which titanium-rich lava solidified into orange-colored glass beads which discolored the ground. It was not only Jack Schmitt who was wildly enthusiastic about their discovery.

When Gene Cernan followed Schmitt up the ladder of the lunar module on December 14, 1972, he was the last of the twelve astronauts of the six lunar landing missions to leave a footprint behind. The words he spoke before he did so were as remarkable as those of Neil Armstrong in 1969 but are far less popular: “We leave as we came, and God willing, as we shall return with peace and hope for all mankind.”

At 23:55 CET, Cernan and Schmitt lifted off from the lunar surface for the command module in which Ron Evans had been carrying out experiments during his 75 lunar orbits. On December 19, 1972, at 20:24:59 CET, Apollo 17 splashed down in the Pacific. The Apollo project, one of mankind‘s greatest adventures, was over; for Gene Cernan it was “the end of the beginning” of the exploration of the Moon.

The texts presented here were created by the DLR Institute of Planetary Research and space expert Gerhard Daum for the exhibition ‘Apollo and Beyond’ at the Technik Museum Speyer. Among other things, the history of the Apollo programme is showcased in detail using both text and images. In addition, full-scale models of the Apollo 11 Lunar Module ‘Eagle’, the Apollo 15 Lunar Roving Vehicle and an Apollo space suit for visiting the Moon’s surface, as well as a 3.4-billion-year-old rock collected from the Apollo 15 landing site can be seen in a lunar landscape.

Contact
  • Ulrich Köhler
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Plan­e­tary Re­search
    Rutherfordstraße 2
    12489 Berlin
    Contact
  • Elke Heinemann
    Ger­man Aerospace Cen­ter (DLR)

    Com­mu­ni­ca­tions and Me­dia Re­la­tions
    Telephone: +49 2203 601-2867
    Linder Höhe
    51147 Cologne
    Contact
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