The geologic investigation of the Taurus-Littrow Valley; Apollo 17 landing site, with a section on Apollo 17 lunar surface photography

Abstract

Astronauts Cernan and Schmitt, of Apollo 17, landed in the Taurus-Littrow valley of the Moon on December 11,1972. Their major objectives were (l) to sample very ancient lunar material such as might be found in pre-Imbrian highlands as distant as possible from the Imbrium basin and (2) to sample pyroclastic materials that had been interpreted as significantly younger than the mare basalts re turned from previous Apollo landing sites. The crew worked approx imately 22 hours on the lunar surface; they traversed about 30 km, collected nearly 120 kg of samples, took more than 2,200 photo graphs, and recorded many direct geologic observations. The lunar surface data, sample results, and geologic interpretation from orbital photographs are the bases for this geologic synthesis.The Taurus-Littrow massifs are interpreted as the upper part of the thick, faulted ejecta deposited on the rim of the transient cavity of the large southern Serenitatis basin, which was formed about 3.9 to 4.0 b.y. ago by the impact of a planetesimal. The target rocks, pre dominantly of the dunite-anorthosite-norite-troctolite suite or its metamorphosed equivalents, were fractured, sheared, crushed, and melted by the impact. The resulting mixture of crushed rock and melt was transported up and out of the transient cavity and depos ited on and beyond its rim. Hot fragmental to partly molten ejecta and relatively cool cataclasite and relict target rocks were intermixed in a melange of lenses, pods, and veins. Crystallization of melts and thermal metamorphism of fine-grained fragmental debris produced breccia composed of rock and mineral fragments in a fine-grained, coherent, crystalline matrix. Such breccia dominates the massif samples.High-angle faults that bound the massifs were activated during formation of the basin, so that structural relief of several kilometers was imposed on the ejecta almost as soon as it was deposited. Mas sive slumping that produced thick wedges of colluvium on the lower massif slopes probably occurred nearly contemporaneously with the faulting. Material of the Sculptured Hills, perhaps largely cataclasite excavated from the southern Serenitatis basin by the same impact, was then deposited on and around the massifs.Basalt, estimated to be about 1,400 m thick in the landing site, flooded the Taurus-Littrow graben before approximately 3.7 b.y. ago. The basalt (subfloor basalt) is part of a more extensive unit that was broadly warped and cut by extensional faults before the accumula tion in Mare Serenitatis of younger, less deformed basalts that over lap it. A thin volcanic ash unit, probably about 3.5 b.y. old, mantled the subfloor basalt and the nearby highlands. It, too, was sub sequently overlapped by the younger basalt of Mare Serenitatis.In the time since deposition of the volcanic ash, continued bom bardment by primary and secondary projectiles has produced regolith, which is a mechanical mixture of debris derived mainly from the subfloor basalt, the volcanic ash, and the rocks of the nearby massifs and Sculptured Hil...

Complex history of a zircon aggregate from lunar breccia 73235

“…Based on chemistry, Rhodes et al (1974) classified the rock as a KREEP-like noritic breccia. Dence et al (1976) and Wolf (1981) concluded that samples collected at the Apollo 17 Taurus-Littrow site are part of the Serenitatis basin ejecta sequence. However, Spudis and Ryder (1981) suggested that the breccia probably includes exotic components as well as reworked local material.…”

“…Aphanetic melt breccia 73235 has been interpreted as a melt product of the Serenitatus basin impact (Dence et al, 1976;Wolf, 1981) although Spudis and Ryder (1981) argue that the Apollo 17 melts display much greater compositional diversity that would a single impact melt sheet and favour generation of the diverse melt rocks by multiple impacts. Nevertheless, the consistency of 40 Ar/ 39 Ar ages of ca.…”

“…73235 is one of several samples (including 73215, 73217 and 73255) recovered from the rim of a 10 meter crater into landslide material off the South Massif (Wolf, 1981). The rock sample is a clast-rich aphanitic melt breccia with a variety of mineral and lithic clasts comprising about 75% dense matrix, 10% lithic clasts larger than a few millimetres across, and 15% mineral clasts larger than about 0.05 mm (Spudis and Ryder, 1981;Ryder, 1993).…”

Subsurface density structure of Taurus‐Littrow Valley using Apollo 17 gravity data

“…From conventional faulting theory, we expect this angle to be close to 60° [ Thatcher and Hill , ]. However, an extended time period between the graben formation and the basalt infill was likely [ Wolfe et al , ], and thus, we expect the angle to have shallowed through mass wasting toward its angle of repose, and possibly beyond this angle by impact gardening and seismic shaking by impacts [ Fassett and Thomson , ; Kreslavsky and Head , ].…”

Space weathering on the Moon: Patina on Apollo 17 samples 75075 and 76015

“…The polished thin sections consists mostly of pyroxene, plagioclase, and ilmenite, with minor olivine and small amounts of armalcolite, interstitial silica, troilite, and Fe-Ni metal (Neal and Taylor, 1993). Because 75075 was found as a loose fragment on a boulder, and because its composition is different from the other Station 5 basalts (75015, 75035, and 75055), which are thought to represent Camelot subfloor material, it is thought that 75075 was emplaced at Station 5 by a post-Camelot impact event (Wolfe et al, 1981). Macroscopically (Fig.…”