Guest “What a field trip!” by David Middleton
On December 7, 1972 (a date which should no longer “live in infamy”) at 12:33 a.m. EST astronauts Gene Cernan, Harrison “Jack” Schmitt and Ronald Evans lifted off Kennedy Space Center’s Launch Pad 39A, atop a massive Saturn-V rocket (SA-512) to begin the final (so far) manned space mission to the Moon. This mission is considered by many to be the most successful manned space mission on record.
Apollo 17 Crew
- Commander (CDR) Eugene A. Cernan (left)
- Command Module Pilot (CMP) Ronald E. Evans (center)
- Lunar Module Pilot (LMP)Harrison H. Schmitt (right)
On Aug. 13, 1971, NASA formally announced the crew for Apollo 17, the sixth and final Apollo Moon landing mission, planned for December 1972. The prime crew consisted of Commander Eugene A. “Gene” Cernan, Command Module Pilot (CMP) Ronald E. Evans, and Lunar Module Pilot (LMP) Harrison H. “Jack” Schmitt. Cernan, selected as an astronaut in 1963, would be making his third trip into space, having flown on the Gemini IX mission in 1966 and Apollo 10 in 1969 – the dress rehearsal flight for the first Moon landing. He also served as the backup commander for Apollo 14, but did not fly on the mission. Evans, selected as an astronaut in 1966, would be making his first spaceflight. He served on the support crews for Apollo 7 and 11, and as the backup CMP on Apollo 14. Schmitt, selected in the first group of scientist astronauts in 1965 and making his first trip into space on Apollo 17, served as the backup LMP on Apollo 15. He was the first geologist selected to land on the Moon.
As I write this post, I am 63 years old… I was 13 when Apollo 17 lifted off and totally enthralled with the space program. I still recall the grainy video of Neil Armstrong setting foot on the Moon in 1969 and the better resolution videos of the Apollo 15, 16 and 17 landing crews riding around in the lunar rovers. I still find it hard to accept that we abandoned the Apollo program right when NASA was perfecting the missions. Apollo 15 was the first true science mission J-missions). Apollo 15 and 16 were very successful J-missions, in no small part due to the fact that geologist Jack Schmitt played a huge role in training the crews in field geology. However, Apollo 17 was, in my opinion, the most successful of the J-missions. In 2011, I had the great pleasure in actually meeting Jack Schmitt at the American Association of Geologists (AAPG) convention in Houston, Texas. As a geologist, Apollo 17 holds a special place in my heart (possibly the only space not occupied by Mrs. Middleton and our 12 dogs).
If you have the time, this site is worth tuning in to…
NASA has a brief, but, nice summary of the mission here:
Of course, as a geologist, my primary interests are the geological aspects of the mission. The Lunar and Planetary Institute (LPI) maintains an incredible inventory of lunar regolith and rock samples returned by Apollo and the Soviet-era Luna missions.
The Taurus-Littrow landing site was chosen because it was thought that it would provide opportunities to study mare basalts, deeper crustal rocks and possibly evidence of more recent volcanism.
The Valley of Taurus-Littrow
The Apollo 17 landing site is in a spectacular location called The Valley of Taurus-Littrow on the southeastern edge of the Sea of Serenity (Mare Serenitatis). Sometime about 3.8 to 3.9 billion years ago, a mountain-sized asteroid or comet hit the Moon and blasted out a basin nearly seven hundred kilometers in diameter. Around the rim of Serenitatis, great blocks of rock were pushed out and up, forming a ring of mountains. In places, the blocks quickly fell again, and left radial valleys among the mountains. Taurus-Littrow is one such valley, located just south of Littrow Crater in the southwestern Taurus Mountains ( 0.9 Mb ) that form the highlands east of Serenitatis.
About 100 to 200 million years or so after Serenitatis formed, lavas welled up from the lunar interior and began to fill the low places. Many of the flows first reached the surface at the weak, fractured margins of the basin; and, as Schmitt and Cernan discovered, at some stages the flows were accompanied by fire fountains that blanketed their surroundings with tiny glass beads. Some of the beads were orange in color, but most were very dark. Even from Earth, the borders of Serenitatis look dark and, prior to the mission, there were many who speculated that this was an indication of recent volcanic eruptions.
Taurus-Littrow is elongated on an axis that points northwest toward the heart of Serenitatis. At its inner, southeastern end, the valley butts up against a large, blocky mountain called the East Massif. Toward the south, a narrow outlet – partially blocked by a large crater – leads off to another valley. On the west side of this outlet, a second blocky mountain called the South Massif forms the southwestern wall of Taurus-Littrow. North of the East Massif, across an outlet into another small valley, the Sculptured Hills and farther to the west, the North Massif form the remaining walls of Taurus-Littrow. Between the North and South Massifs, the main exit from the valley leads out toward Serenitatis. This exit is about seven kilometers wide and is partially blocked by a kilometer-high hill called Family Mountain and, also, by a fault scarp that stretches between the North and South Massifs. In places, the scarp is 80 meters high.
The inherent geologic variety of Taurus-Littrow was a major reason for the selection of the site. From a landing point out in the middle of the valley, the crew could sample the dark soil, collect samples of the valley-filling lavas dug out by impacts, and sample pre-Serenitatis crustal material in both the North and South Massifs. Of particular interest were a number of large boulders seen in Apollo 15 orbital photographs of the lower slopes of the Massifs. Some of these boulders are sitting at the ends of tracks which show that they had rolled down from outcrops high on the mountains. Additional points of interest included a South Massif avalanche that drapes across the southern end of the scarp, and an intriguing crater called Shorty which sits like a dark blemish at the northern tip of the landslide outflow. Here, some of the geologists thought, might be a young volcanic vent. And finally, there were the Sculptured Hills which, from orbit, look as though they are not directly related to the Massifs and the Serenitatis impact but, rather, it was thought, might represent ejecta from the more recent Imbrium impact.
During the preceding missions, none of the crews that attempted pinpoint landings actually landed farther than about a half-kilometer from their target. Of course, as had happened in case of Apollo 11, larger errors were possible, particularly if the flight-path could not be updated during the powered descent; and NASA wanted to be sure that Cernan would be able to land even if Challenger were headed as much as four kilometers long or short of the target and as much as three kilometers to either side. Taurus-Littrow is not a large valley; and, indeed, the Apollo 17 crew was able to cover nearly half of it during their three geology trips. Still, it is large enough to contain the landing ellipse and several more besides. The actual target point was on the valley’s central axis, well away from the Massifs, and about six kilometers short of the scarp. This northwestward placement was chosen so that the crew would fly over the Sculptured Hills at substantial altitude as they entered the valley and, later, could drive to the foot of the South Massif without violating walkback constraints. In detail, the target area is a relatively smooth patch of ground in the midst of a cluster of large craters. The largest of these is Camelot Crater, about 600 meters across, and it promised good samples of the valley fill. Camelot is about a kilometer west of the target and provided Cernan with a visual fix at pitchover. Closer at hand, he had a trio of small craters called Punk, Rudolph, and Poppie to show him exactly where to land. He wanted to land midway between Poppie and Punk and just south of Rudolph.
The rocks and regolith samples collected by Cernan and Schmitt generally fell into three categories: basalts, breccias, and highland crustal rocks.
Some of the deep crustal rocks were fairly unusual compared to other crustal samples.
The Apollo 17 crew also collected several rare types of lunar rock, including norite, troctolite, and dunite, at stations 2, 6, and 8 near the base of the North and South Massifs and the Sculptured Hills. Norite consists primarily of the minerals plagioclase and orthopyroxene. Troctolite consists primarily of plagioclase and olivine, and dunite is nearly pure olivine. Many of these rocks originally formed in the lower half of the Moon’s crust during the solidification of the Moon’s magma ocean. These rocks formed between 4.2 and 4.5 billion years ago (the solar system formed about 4.56 billion years ago). They were later brought to the Moon’s surface by large meteorite impacts, such the impact that formed the Serenitatis basin.
One of the most interesting discoveries was the “Orange Soil“, initially interpreted by Schmitt as the result of a fumarole and evidence of recent volcanism.
However, it turned out to be ancient volcanic glass.
Mare basalts were emplaced as fluids that flowed easily across the Moon’s surface. However, photographs taken from lunar orbit suggested that some explosive volcanic activity had also occurred in this region, and some geologists thought this activity might have occurred recently in lunar history. Shorty Crater was explored to determine if it was actually a volcanic vent. Orange and black volcanic glass (the famous “orange soil”) was found near the rim of Shorty Crater and did form in an explosive volcanic eruption. On Earth, such eruptions are sometimes called fire fountains. However, the relationship between Shorty Crater and the volcanic glass is just coincidental. The glass formed 3.64 billion years ago from material that melted about 400 kilometers below the surface. Shorty Crater turns out to be an ordinary impact crater, and the lack of degradation of its features indicates that the crater is much younger than the glass.
Setting records on the Moon
Gene Cernan and “Jack” Schmitt set records that have stood for 50 years: 75 hours on the lunar surface, with three extra-vehicular activities EVA’s in the lunar rover (LRV), comprising over 22 hours. The second EVA was truly remarkable.
The second EVA was the longest of the Apollo program both by duration, 7 hours and 37 minutes, and by traverse distance, 20.4 km roundtrip, reaching a maximum distance of 7.6 km from the Lunar Module at Station 2. It was likely also the most complex EVA of Apollo based on the diversity of the geologic targets. Cernan and Schmitt began by repairing the right rear fender of the rover using laminated maps and small clamps. The fender had been damaged when snagged by a rock hammer during EVA 1. The repair substantially reduced the amount of dust that the rover kicked up while driving. Stations 2 and 3 were on a landslide at the base of the South Massif. The mountains surrounding the landing site were uplifted by the impact that formed the Serenitatis impact basin, and the boulders on the landslide gave the crew to access to material that had originally been located far up the South Massif slope. Stations 4 and 5 were on the valley floor while returning to the Lunar Module. Shorty Crater (Station 4) was suspected prior to the mission to be a possible volcanic vent due to the dark halo surrounding the crater. Schmitt discovered orange soil, which turned out to be 3.6 billion-year-old pyroclastic glass from an ancient volcanic eruption. Camelot Crater (Station 5) is 600 meters in diameter with a very rocky rim. The ejecta at the edge of the crater provided samples of basalt that was originally more than 100 meters below the valley floor.
In addition to the successful geological traverse, Commander Cernan also managed to both damage and repair the rover…
At 118:51:20, while doing final Rover preparations before driving out to meet Jack Schmitt at the ALSEP deployment site, Gene Cernan accidentally caught the hammer he had stowed in his calf pocket under the right rear fender, tearing off the rearward extension. He used grey duct tape to re-attach the fender extenstion but, at about 122:47:48 during the drive back to the LM from Station 1 at the end of the EVA, the tape failed and the fender extension fell off.
Gene and Jack did not stop to retrieve the fender extension and, during the rest period after EVA-1, support personnel in Houston designed a replacement fender that Gene and Jack could make from tape, unneeded maps, and some clamps they had in the cabin. See the discussion at 137:19:09.
A detail from AS17-137-20979 is presented at the top of this page, showing the replacement fender on the Rover just before Gene and Jack leave Station 2. At the time Gene took the picture, the replacement fender had been tested during 9.1 km of driving.
At about 167:41:11, during the drive to Station 9 late in EVA-3, the replacement fender began to fail, perhaps due to the combined effects of prolonged solar heating and the dust and rock fragments thrown against its underside during the total of about 29 km of driving they’d done since Gene installed it.
Later, after parking the Rover east of the LM so that the world could watch LM liftoff with the Rover TV, Gene removed the replacement fender and brought it back to Earth. As of September 2005, it was still on display at the Smithsonian’s National Air and Space Museum.
In just over 22 hours of EVA’s, Cernan and Schmitt traveled over 22 miles across the lunar surface. Only Lunokhod 2 and Opportunity traveled farther. However, Lunokhod 2 operated on the lunar surface for four months and Opportunity spent about 14 years covering 28 miles on the surface of Mars.
Don’t hit the Lem!
Shortly before departing the lunar surface, Jack Schmitt probably set the record for the longest rock hammer throw in geological history…
170:29:49 Schmitt: Let me throw the hammer? Please.
170:29:50 Cernan: It’s all yours.
170:29:51 Schmitt: You got the gravimeter
170:29:52 Cernan: You deserve it. A hammer thrower…You’re a geologist. You ought to be able to throw it.
170:29:56 Schmitt: You ready?
170:29:57 Cernan: Go ahead.
170:29:58 Schmitt: You ready for this? Ready for this?
170:30:00 Cernan: Yeah. Don’t hit the LM. Or the ALSEP. (Pause)
[Jack throws the hammer with a discus motion. It is visible against the sky for a long time. Gene’s picture of Jack, AS17-143-21941 may have been taken just after he threw the hammer.]
170:30:07 Cernan: Look at that! Look at that! Look at that!
170:30:12 Schmitt: Beautiful.
170:30:14 Cernan: Looked like it was going a million miles, but it really ‘t.
170:30:17 Schmitt: Didn’t it?