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At least 109 records · Page 6

U-Th-Pb and Rb-Sr systematics of Apollo 17 boulder 7 from the North Massif of the Taurus-Littrow valley

Portions of highland breccia boulder 7 collected during the Apollo 17 mission were studied using U-Th-Pb and Rb-Sr systematics. A Rb-Sr internal isochron age of 3.89 plus or minus 0.08 b.y. with an initial Sr-87/Sr-86 of 0.69926 plus or minus 0.00008 was obtained for clast 1 (77135,57) (a troctolitic microbreccia). A troctolitic portion of microbreccia clast 77215,37 yielded a U-Pb internal isochron of 3.8 plus or minus 0.2 b.y. and an initial Pb-206/Pb-207 of 0.69. These internal isochron ages are interpreted as reflecting metamorphic events, probably related to impacts, which reset Rb-Sr and U-Pb mineral systems of older rocks.

Nunes, P. D.↗

Petrology of a stratified boulder from South Massif, Taurus-Littrow

Boulder 1 from Station 2 at the foot of South Massif is unique in being the only stratified boulder sampled by the Apollo 17 astronauts. Our studies of two of the four specimens that were collected from separate layers show that the boulder is composed of glass-poor, fragment-rich breccias which are aggregates of differentially annealed terra material, mainly ANT, but including basaltic troctolite, pigeonite basalt, granitic particles, dark breccia-rimmed anorthositic clasts, and a KREEPless norite that has not been recognized elsewhere at the Apollo 17 site. The boulder appears to derive from the uppermost blue-gray layer on South Massif, which we believe consists of ejecta deposited from a single large impact event (possibly the one which excavated the Serenitatis Basin).

Stoeser, D. B.↗

Mare basalts from the Taurus-Littrow region of the moon

Two distinct chemical basalt types have been sampled at the Apollo 17 landing site. Very high-titanium basalts (about 13 wt % TiO2) are the dominant type and display a textural range from olivine-porphyritic, ilmenite vitrophyres to plagioclase-poikilitic, ilmenite microgabbros. Most of these rocks could have come from one flow. These basalts appear to represent partial melts from feldspar-ilmenite cumulates with an Ar-40/Ar-39 age of about 3.7 G.y., which have experienced little, if any, near-surface fractionation of olivine and Fe-Mg-Ti oxides. A second type of basalt virtually identical to the Apollo 11 (low-K) basalts is much less common.

Papike, J. J.↗

Petrology of the highlands massifs at Taurus-Littrow - An analysis of the 2-4 mm soil fraction

The petrography, phase chemistry, and Ar-40/Ar-39 ages of 2-4 mm fragments from the soils of both mare and highlands stations sampled by Apollo 17 are studied. It is found that the massifs consist of a complex stratigraphy of interlayered noritic breccias of varying metamorphic grades, melt rocks, and anorthositic rocks. A stratigraphic correlation of the lithologies within the North Massif and the South Massif is carried out. The petrogenesis of rock types with respect to thermal and impact history is discussed. The observed spinel cataclasites may represent relatively deep material sampled by the Serenitatis event.

Bence, A. E.↗

Taurus-Littrow chronology - Some constraints on early lunar crustal development

A number of samples obtained during the Apollo 17 mission give direct evidence of lunar processes occurring more than 4 aeons ago. The significance of Rb-Sr data for the history of the involved materials is discussed and mineral isochrons are presented for an Apollo 17 mare basalt. Data on a number of Apollo 17 soils and on some Apollo 15 and 16 whole-rock samples are also presented.

Nyquist, L. E.↗

Sulfur abundances and distributions in the valley of Taurus-Littrow

Total sulfur abundances have been determined for 36 Apollo 17 soil, breccia and crystalline rock samples. Sulfur concentrations range from 550 to 1300 micrograms S/g for soil samples, with the orange soil containing the lowest amount of sulfur. Noritic breccias contain between 720 and 950 micrograms S/g, while the anorthositic rocks have sulfur contents of 270 and 368 micrograms S/g. The dunite 72415 contained the lowest sulfur content (44 micrograms S/g) of any Apollo 17 sample studied. Apollo 17 basalts have unusually high sulfur contents (1580-2770 micrograms S/g) as compared to Apollo 12 and 15 basalts and terrestrial basalts. Sulfur abundances for the Apollo 17 basalts are almost identical to those from Apollo 11 basalts. A negative correlation between percent metallic iron and total sulfur for the Apollo 17 and 15 basalts was found and suggests that a portion of the metallic iron in lunar basalts may result from desulfuration of the melt prior to crystallization from the lunar magma.

Gibson, E. K., Jr.↗

Geological model for Boulder 1 at Station 2, South Massif, Valley of Taurus-Littrow

A possible geological model for the origin and history of the materials that make up Boulder 1 is proposed on the basis of firm and probable regional, local, and boulder geological constraints. These constraints are described in detail, unresolved questions are considered, and a model is presented which appears to satisfy all the firm constraints and most of the probable constraints. According to this model, the crystallization of plagioclase and other ANT-suite phases now present in the boulder as clasts and matrix materials took place during the melted-shell stage of lunar history; the original rocks were greatly modified during the cratered-highland stage; and the events that determined the major characteristics of the boulder occurred during the large-basin stage.

Schmitt, H. H.↗

Evidence for detection of 1-10 MeV emission from the Taurus region in 1971 August

Results are reported for three observations of the Crab Nebula with a balloon-borne actively collimated NaI detector over the energy range from 0.2 to 10 MeV. Possible changes in instrument performance and environmental background levels during the balloon flights are investigated, and fits for source strength are made over four broad energy channels. X-ray power-law spectra and pulsed-flux fractions are determined for both the Crab Nebula and its pulsar, NP 0532. A statistically significant flux greatly in excess of the power law was detected above 1 MeV during one flight; this flux, which has declined by at least a factor of 4 or 5 at the times of more recent observations, is assumed to be real and is attributed to the nebula.

Gruber, D. E.↗

Large and small scale structures of molecular clouds in the Taurus Perseus complex

The gaseous components studied in H I and OH absorption against the extragalactic radiosources 3C123 and 3C111 are found to be the low-density edges of condensations of a few 100 solar masses. The densest part of one of these condensations has a structure similar to that found in other dark clouds: it is fragmented into several cores of a few solar masses, with an orbital velocity dispersion of about 2 km/s. In turn, the extended low-density layer, optically thick in CO (2-1), is not a common feature. It depends on the ambient UV field, but the dust temperature in the core may control its existence. Even more critically; it is found that the lower is the dust temperature, the less massive is the core and the more extended is the envelope around it, for a given total mass in a given external pressure.

Falgarone, E.↗

An X-ray survey for pre-main-sequence stars in the Taurus-Auriga and Perseus molecular cloud complexes

Seventy-five fields from the Einstein X-Ray Observatory IPC detector between 3h and 5h right ascension and 15 deg and 35 deg declination are examined to search for X-ray-emitting low-mass pre-main-sequence (PMS) stars. Six such stars were previously found; they appear to be similar to T Tauri stars but without dense circumstellar envelopes or winds. Finding charts are presented for 59 X-ray sources that may be PMS stars. While some are likely to be spurious X-ray sources, chance coincidences with unrelated stars, or non-PMS stellar sources such as RS CVn type binaries, approximately half are probably X-ray-selected PMS stars.

Feigelson, E. D.↗

X-ray sources in regions of star formation. III - Naked T Tauri stars associated with the Taurus-Auriga complex

Ground-based and IRAS optical and IR spectroscopic and photometric observations are reported for 90 stars in or near 59 Einstein Observatory X-ray error circles in the Tau-Aur region. The data are presented in extensive tables and sample spectra and characterized in detail, with particular attention to 28 newly discovered 'naked' T Tau stars, which are shown to be normal stars with no significant IR or UV excess and ages of 1-40 Myr. These stars are found to outnumber normal T Tau stars by a factor of 10 in an area near the Tau-Aur dark clouds, and it is argued that their evolution toward the ZAMS is typical for low-mass stars. The implications of this finding for the time scales of circumstellar-disk dissipation and planet formation are discussed.

Walter, Frederick M.↗

A reexamination of luminosity sources in T Tauri stars. I - Taurus-Auriga

An analysis is presented of 72 T Tau stars identified by IRAS in the Tau-Aur complex. The composite energy distributions of the stars are constructed to define bolometric luminosities and the luminosity components in different spectral regimes are separated. The near- to far-IR spectral indices of these stars are analyzed. It is shown that 2/3 of typical T Tau stars have a bolometric to stellar luminosity ratio of about 1.0, which implies no appreciable disks. The distribution is bimodal, however, with a second peak at about 2.0, suggesting that 1/3 of the stars have disks. The bolometric luminosities of the north and south components of T Tau are found to be in the range of 9-21 solar luminosities and 1.5-14 solar luminosities for T Tau N and T Tau S, respectively.

Cohen, Martin↗

Star formation in Taurus-Auriga - The high-mass stars

The question of whether the star formation in the Tau-Aur clouds produces low-mass stars exclusively is considered. The paper identifies 29 B stars as possible kinematic members of the T association, and it is argued that the data are consistent with the existence of a single initial mass function (IMF) generating the low and high-mass stars. It is concluded that the Tau-Aur T association is related to the Cas-Tau OB association, and there is no evidence that the association IMF differs from the field star IMF.

Walter, Frederick M.↗

Compositional variations in Apollo 17 soils and their relationship to the geology of the Taurus-Littrow site

New compositional data for major and trace elements in Apollo 17 solids are combined with data from the literature in order to constrain a mass-balance model that accounts for the compositions of most solids as mixtures of a small number of lithologic components observed at the site. Variation in the proportions of six chemical components accounts for most of the compositional variation in the solids. Each of the components is represented by lithological components observed in the regolith. Three of the chemical components are of mare origin: high-Ti mare basalt, LTV basalt, and pyroclastic orange glass. Three are of highland origin: noritic impact-melt breccia, anorthositic norite breccia, and high-Mg/Fe troctolites and norites. Results from a six-component mass-balance model indicate that VLT basalt composes only about 8 percent of the total basalt component, while orange glass composes up to 26 percent of some solids. The troctolite/norite component is only important in soils from the North Massif.

Korotev, Randy L.↗

The Serenitatis Basin and the Taurus-Littrow highlands: Geological context and history

The Apollo 17 mission was targeted to land at the southeastern edge of the Serenitatis Basin, one of a number of large impact basins on the Moon. The geologic setting of the Apollo 17 site is reviewed, the implications for the formation of basins from Apollo 17 results are assessed, and unanswered questions potentially addressable with existing and new data are outlined.

Head, James W.↗