Engineering topics

Spudis, P. D.

Publications and source records attributed to Spudis, P. D..

At least 37 records · Page 2

NASA NTRS1992

The distribution of anorthosite on the nearside of the moon

Remote sensing studies of lunar basin and crater deposits were conducted in order to determine the composition of surface units and to investigate the stratigraphy of the lunar crust. These studies have combined both visible and near-IR spectral observations with multispectral imaging in order to determine the lithology of relatively small portions (2-10 km) of the lunar surface. Numerous deposits of pure anorthosite (plagioclase greater than 90 percent) were identified and an interesting pattern has emerged. The purposes of this report are as follows: (1) to summarize the results of our previous studies of the distribution of anorthosite; (2)to present new findings concerning the modes of occurrence of lunar anorthosite; and (3) to assess the implication for the magma ocean hypothesis.

Hawke, B. R.↗

NASA NTRS1992

Lunar Base Siting

There are widely dispersed lunar sites of interest for known and potential resources, selenology and observatories. Discriminating characteristics include certain geologic and topographic features, local mineralogy and petrology, solar illumination, view of Earth and the celestrial sphere, and soil engineering properties.

Lunar↗

NASA NTRS1991

Remote sensing and geologic studies of the orientale basin region

Both visual and near-infrared spectral observations are combined with multispectral imaging to study the Orientale interior and exterior, the Cruger region, Grimaldi Region, the Schiller-Schickard Region, and the Humorum Region of the Moon. It was concluded that anorthosites occur in the Inner Rook Mountains of Orientale, the inner ring of Grimaldi, and the main ring of Humorum. Imaging spectroscopy shows that the entire eastern Inner Rook Mountains are composed of anorthosites. Orientale ejecta are strikingly like the surface materials in the region where Apollo 16 landed. This similarity indicates similar mineralogy, i.e., noritic anorthosite. Thus, Orientile ejecta is more mafic than the Inner Rook Mountains. This situation is also true for the Nectaris, Humorum, and Gramaldi basins. Isolated areas of the Orientale region show the presence of gabbroic rocks, but, in general, Orientale ejecta are noritic anorthosites, which contain much more low-Ca pyroxene than high-Ca pyroxene. Ancient (pre-Orientale) mare volcanism apparently occurred in several areas of the western limb.

Hawke, B. Ray↗

NASA NTRS1991

Remote sensing and geologic studies of the terrain northwest of Humorum basin

A portion of the highlands terrain northwest of the Humorum basin, a large multiringed impact structure on the southwestern portion of the lunar nearside, exhibits anomalous characteristics in several remote sensing data sets. A variety of remote sensing studies of the terrain northwest of Humorum basin were performed in order to determine the composition and origin of the anomalous unit as well as the composition of the highland material exposed by the Humorum impact event. It was found that at least a portion of the mare-bounding ring of Humorum is composed of pure anorthosite. Other details of the study are reported.

Hawke, B. Ray↗

NASA NTRS1991

Sources of mineral fragments in impact melts 15445 and 15455 - Toward the origin of low-K Fra Mauro basalt

The compositions of major and minor elements in mineral clasts in low-K Fra Mauro (LKFM) are studied in order to gain a deeper understanding of the genesis of LKFM and its primogenitors. The fragments are picked up as the impact melt moves outward from the center of the target. It is suggested that most of the mineral debris found in the melts is derived from troctolites of the Mg-suite. The chemical end member that dominates the LKFM melt matrics is not present as either mineral or lithic clastic debris in these melt rocks. It is proposed that the missing chemical component of LKFM could have been a magma, existing within the crust 3.9 Ga ago, and was either ejected intact to form LKFM melt rocks or was mixed with other shock-melted crusted and mantle rocks to produce the LKFM compositions. Assimilation of lithic and mineral clasts into the melt after breccian assembly is not a significant process and cannot be adduced to explain the LKFM melt/clast dichotomy.

Spudis, P. D.↗

NASA NTRS1991

Searching for Crisium Basin ejecta - Chemistry and ages of Luna 20 impact melts

Chemical (INAA) and chronological (Ar-40 - Ar-39) analyses of six Luna 20 impact melts are performed, and these are compared to the results of Podosek et al. (1973), commonly taken to be representative of the Crisium Basin impact. At least two chemical groups of impact melts are identified. One is interpreted as melts derived from the local crust by craters over the last 3.9 Ga. Another group, which includes one of the samples dated by Podosek et al. (1973), is chemically and chronologically (3.85 + or - 0.02 Ga) indistinguishable from Apollo 17 samples interpreted as Serenitatis impact melts, and hence could be melt formed by that event and deposited at the Luna 20 site. One sample (22023,3,F) has a well-defined age of 3.895 + or - 0.017 Ga, and is chemically similar to, but distinct from, impact melts from other basins. This sample, and its chemistry and age are tentatively identified with the Crisium Basin impact. Whether the age of the Crisium impact is given by 22023,3,F, the samples analyzed by Podosek et al. (1973), or neither, it is clear that Crisium impact melt is not abundant in the Luna 20 collection.

Swindle, T. D.↗

NASA NTRS1989

Geology and deposits of the lunar Nectaris basin

The geology and composition of Nectaris basin deposits have been investigated in order to provide information on the lunar basin-forming process and the regional geologic setting of the Apollo 16 landing site. Several outcrops of nearly pure anorthosite were noted in locations such as the walls of Kant crater, an inner ring of the basin, and the crater Bohnenberger F. The results suggest that the impact can be modeled as a proportional-growth crater, and that the Nectaris excavation cavity was about 470 km in diameter and as deep as 55 km.

Spudis, P. D.↗

NASA NTRS1989

Sources of clasts in terrestrial impact melts - Clues to the origin of LKFM

Low-K Fra Mauro (LKFM) 'basalt', which is found exclusively as an impact melt rock, cannot be modeled geochemically from its clast population or from any combination of known pristine lunar rock types. To clarify clast/melt relationships, a study was made of impact melt rocks from Mistastin Lake crater, Labrador, where there are only three target rocks: anorthosite, quartz monzonite, and granodiorite. Feldspar compositions in these rocks define distinct fields on the An-Ab-Or ternary diagram, making it possible to identify the source of each feldspar clast. Clasts in the Mistastin impact melts do not reflect the abundance of target rocks melted during the impact. The abundance of anorthosite in the clast population varies from 34 to 100 percent compared to a relatively constant value of 65 percent calculated to be in the melt matrix. Therefore the clasts appear to be derived predominantly from material relatively far removed from the zone of impact melting. Melt-matrix composition is dictated strictly by the composition of the target materials within a small radius around and below the point of impact. This suggests that the LKFM composition was derived from a lower crustal source.

Mccormick, K. A.↗

NASA NTRS1985

Geology and petrology of the Apollo 15 landing site - Past, present, and future understanding

The main objectives of the Apollo 15 lunar mission were to investigate and sample materials from the Apennine Front (expected to be Imbrium ejecta and pre-Imbrian materials), the Hadley Rille, and the mare lavas of Palus Putredinis. The Hadley Rille was found to be a collapsed lava tube or channel, and from it, many mare basalt samples were collected which form two main chemical groups of the same age (3.3 b.y.), isotopic characteristics, and rate-earth element patterns. One group, olivine-normative, contains many vescular specimens and shows an olivine fraction trend. The other group, quartz-normative, is pigeonite-phyric and contains both vitrophyric and coarse-grained samples but exhibits little fractionation. The Apennine Front samples include such highland materials as ferroan anorthosites, spinel-bearing troctolites, norites, impact melts and metamorphosed breccias. A conspicuous component of the regolith breccias is volcanic green glass. The Apennine Front is characterized by a low-KREEP composition, a composition which has never been found as a pristine igneous rock type. Another unexpected discovey was the common occurrence of 3.5 b.y. old volcanic KREEP basalts. It is concluded that all major lunar processes can be profitably studied from the samples and observations at this single location.

Spudis, P. D.↗

NASA NTRS1985

The origin of selected lunar geochemical anomalies Implications for early volcanism and the formation of light plains

The geochemical anomalies on the eastern limb and far side of the moon are presently identified and characterized, and their formation processes are investigated, in light of Apollo spacecraft geochemical and photogeologic remote sensing data sets. The results of recent spectral reflectance studies of dark-haloed impact craters, together with considerations of anomaly surface chemistry, indicate that the geochemical anomalies associated with light plains deposits displaying dark-haloed impact craters are due to basaltic units that are either covered by varying thicknesses of highland debris or have a surface contaminated by significant amounts of highland materials.

Hawke, B. R.↗

NASA NTRS1985

Average Spacing for Rings of Individual Multi-ring Basins Is 2.0(0.5)D

The mathematically regular spacing of the concentric rings of planetary impact basins are examined. It is shown that a constant radial increment of x (sub 0.5) D, where x is about 2.0 and D is ring diameter, separates adjacent statistical groups of rings and arcs of multiring basins on Mars, Mercury, and the Moon. Statistics of spacing for adjacent rings of individual basins on the three planets are presented, and single basins from ring measurements of newly-recognized basins on Mercury and Mars are revised. Analysis of ring rank: ring diameter for adjacent rings of individual basins also yields an average spacing of about 2.0 (sup 0.5) D, specifically (2.01 + or - 0.26) (sup 0.5) D.

Pike, R. J.↗

NASA NTRS1985

Ring-diameter Ratios for Multi-ring Basins Average 2.0(0.5)D

The spacing of the concentric rings of planetary impact basins was studied. It is shown that a radial increment of x (sup 0.5) D, where x is about 2.0 and D = ring diameter, separates both (1) adjacent least-squares groups of rings and arcs of multi-ring basins on Mars, Mercury, and the Moon; and (2) adjacent rings of individual basins on the three planets. Statistics for ratios of ring diameters are presented, the first and most-applied parameter of ring spacing. It is found that ratios excluding rings flanking the main ring also have a mean spacing increment of about 2.0. Ratios including such rings, as for the least-squares groups, and (1) above, have a larger increment, averaging 2.1. The F-test indicates, that these spacings of basin ring locations, and mode of ring formation are controlled by the mechanics of the impact event itself, rather than by crustal properties.

Pike, R. J.↗

NASA NTRS1985

Spectral Reflectance Studies of the Orientale Basin

Twelve near-infrared spectra were obtained at the Mauna Kea Observatory 2.2-m telescopy using the Planetary Geosciences Division indium antimonide spectrometer. These include spectra obtained for two fresh surfaces on the inner Rook ring, two fresh craters in the outer Rook Mts., and two inner Rook ring, two fresh craters in the outer Rook Mts., and two fresh 11-km. craters (Eichstadt G and H) which are located between the outer Rook ring and the Cordillera ring and exposed material from within the knobby facies of the Montes Rook Formation. In addition, spectra were collected for portions of the Maunder Formation. Special attention was paid to the spectra collected for six immature features within the Cordillers ring. Analyses of the 1-micron band positions and shapes as well as continuum slopes indicate that the spectra for craters in the knobby facies and in the outer Rook Mts., while differing in detail, exhibit many common spectral characteristics. These spectra represent relatively fresh highlands rocks dominated by abundant Fe-bearing plagioclase feldspar and Ca-poor orthopyroxene. Compositions ranging between noritic anorthosite and anorthositic norite are indicated.

Hawke, B. R.↗

NASA NTRS1985

Hadley Rille, lava tubes and mare volcanism at the Apollo 15 site

Hadley Rille appears to be a collapsed lava tube/channel, whose formation history may be more intimately related to the mare units sampled at 15 than was previously thought. More work is needed relating samples and observations from Apollo 15 to the rille and its geologic evolution. As the only sinuous rille visited during the Apollo missions, Hadley Rille represents a data source that is directly applicable to the deciphering of processes involved in lunar mare volcanism.

Greeley, R.↗

NASA NTRS1985

The materials and formation of the imbrium basin

The deposits around the Imbrium basin form a widespread stratigraphic datum, to which other lunar geological units may be relatively dated. More importantly, as a relatively well preserved multi-ring basin, Imbrium provides an important target of geologic investigation to study the processes involved in lunar basin formation and evolution. Two Apollo missions (Apollo 14 and 15) were send to landing sites chosen specifically to address problems of the Imbrium basin geology. Data about the deposits of the Imbrium basin are reviewed. Formational mechanics of lunar basins in general and the relations of materials collected at the highlands adjacent to the Apollo 15 landing site to Imbrium and other basins are examined.

Spudis, P. D.↗

NASA NTRS1985

The Apennine Bench Formation revisited

The Apennine Bench Formation consists of pre-mare light plains materials that crop out south of the crater Archimedes, inside the Imbrium basin. This material was ascribed to either impact or volcanic origins. The characteristics of Apollo 15 KREEP basalts and the Apennine Bench Formation are reviewed to determine whether their characteristics are compatible with a volcanic origin.

Spudis, P. D.↗

NASA NTRS1985

Advanced geologic exploration supported by a lunar base - A traverse across the Imbrium-Procellarum region of the moon

An example of extended traverse of a lunar region, the Imbrium-Procellarum, for the purpose of geological exploration is described. The necessary field support is discussed, including transportation and logistical support, analytical instrumentation, and field equipment. The various sites of special geological interest in the region are mentioned individually in the order in which they would be visited, indicating what questions are of particular scientific interest at each site.

Cintala, M. J.↗

NASA NTRS1984

Apollo 16 site geology and impact melts - Implications for the geologic history of the lunar highlands

The geology of the Apollo 16 site is reconsidered on the basis of data from photogeology, geochemical remote sensing, and lunar samples. The site possesses an upper surface of anorthositic gabbro and related rocks. Mafic components were deposited as basin ejecta. The events involved in its geological evolution were the Nectaris impact and the Imbrium impact. The role of large, local craters in the history of the region was to serve as topographic depressions to accumulate basin ejecta. The most abundant melt composition at Apollo 16 is an aluminous variety of LKFM basalt supplied by the Nectaris impact as ejected basin impact melt. The mafic LKFM melt may have been supplied by the Imbrium impact. More aluminous melt groups are probably derived from local, small craters. The remainder of the deposits in the region are composed of anorthositic clastic debris derived from the Nectaris basin, the local crustal substrate, and Imbrium and other basins.

Spudis, P. D.↗