3-24

about a half hour of operation, the response changed perceptibly from the full-scale reading. After 7 hours, the indication had decreased to about 3 x lO -9 torr. At the time of lunar module depressurization prior to the second extravehicular activity period, the response increased to at least 7 x lO -8 tort. The exact value is uncertain because a pro- gr_zamed calibration, which time shares the data channel, was being per- formed near the time of maximum pressure. The pressure increase result- ing from lunar module outgassing is in reasonable agreement with predic- tions. Whenever a crewman approached the experiment during the second extravehicular activity period, the instrument response went off-scale, as expected, because of gases released from a portable life support sys- tem.

The stiffness of the electrical cable Joining the cold cathode gage to the suprathermal ion detector experiment caused some difficulty during deployment of the gage (see section lb.3.5). To avoid this problem the tape wrap will be eliminated from future experiment packages and will de- crease the cable stiffness The instrument apparently suffered a cata- strophic failure after about 14 hours of operation, because of a malfunc- tion either in the h.5-kV power supply or in the power-supply switching mechanism.

3.2 SOLAR WIND COMPOSITION EXPERIMENT

The solar wind composition experiment was designed to measure the abundance and the isotopic composition of the noble gases in the solar wind. In addition, the experiment permits a search for the isotopes tritium (H 3) and radioactive cobalt (Co56). The experiment hardware was the same as that flown in Apollo ii and consists of a specially prepared aluminum foil with an effective area of 0.4 square meter. Solar wind particles arrive at velocities of a few hundred kilometers per second and, when exposed to the lunar surface environment, penetrate the foil to a depth of several millionths of a centimeter, becoming firmly trapped. Particle measurements are accomplished by heating portions of the returned foil in an ultra-high vacuum system. The emitted noble gas atoms can be separated and analyzed in statically operated mass spectrometers, and the absolute and isotopic quantities of the particles can then be determined.

The experiment was deployed on the lunar surface and was exposed to the solar wind for 18 hours 42 minutes, as compared to 77 minutes for Apollo ii. Afterward, the foil was placed in a special Teflon bag and returned to earth for analysis.

L U L 3-25

3.3 LUNAR GEOLOGY

Geological information, in the form of voice descriptions, lunar surface samples, and surface photographs, was also provided during all other phases of the surface stay. It appears that the locations and ori- entations of a significant number of the returned samples can be deter- mined relative to their positions on the lunar surface; therefore, de- tailed geologic maps and interpretations can be made from this informa- tion. A summary of the returned lunar surface samples, compared with the Apollo ll samples, is contained in the following table:

Approximate weight, lb Material Apollo 12 Apollo ll

Fines* and chips 12.8 24.2 Rocks 61.0 24.3 Core-tube specimens 0.9 0.3 Total 7_.7 I_8.8

*NOTE: Terms used in this section are defined in a glossary, Appendix F

3.3.1 Ceology of the Landing Site

The lunar module landed on the southeastern part of the Ocean of Storms at ll0-1/2 hours. The coordinates of the landing site are given in section 4.3. This portion of the Ocean of Storms mare is dimpled by many small craters of Copernican and Eratosthenian age, and the landing site is contained within a broad Copernicus ray. The site is located on the northeast rim of the 150-meter-diameter Head crater and the northwest rim of Surveyor crater, in which the Surveyor III unmanned spacecraft landed on April 20, 1967. See figure 3-17 for a traverx_ map of the landing-site area. The surface northwest of the landing site is littered with debris from a 450-meter crater, informally called the Middle Crescent crater, the southeast rim of which lies about 200 meters northwest of the landing site.

On the second extravehicular excursion, the crew visited four craters of over 50 meters in diameter, and many of smaller size. The character- istics of eight craters were described, and a variety of material ejected from each was collected. The crew made numerous comments about smaller craters and about the surface features between them, including ground

I/ ILl. L: L U U. U L: U l/ ]/ L L L