Engineering topics

Spudis, P. D.

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

At least 19 records

NASA NTRS2016

Results of the Lunar Exploration Analysis Group (LEAG) Gap Review: Specific Action Team (SAT), Examination of Strategic Knowledge Gaps (SKGs) for Human Exploration of the Moon

The Lunar Exploration Analysis Group (LEAG) was tasked by the Human Exploration Operations Mission Directorate (HEOMD) to establish a Specific Action Team (SAT) to review lunar Strategic Knowledge Gaps (SKGs) within the context of new lunar data and some specific human mission scenarios. Within this review, the SAT was to identify the SKGs that have been fully or partially retired, identify new SKGs resulting from new data and observations, and review quantitative descriptions of measurements that are required to fill knowledge gaps, the fidelity of the measurements needed, and if relevant, provide examples of existing instruments or potential missions capable of filling the SKGs.

Shearer, C. K.↗

NASA NTRS2016

Identifying and Characterizing Impact Melt Outcrops in the Nectaris Basin

The Nectaris Basin is an 820-km diameter, multi-ring impact basin located on the near side of the Moon. Nectaris is a defining stratigraphic horizon based on relationships between ejecta units, giving its name to the Nectarian epoch of lunar history. Lunar basin chronology based on higher resolution LRO imagery and topography, while assigning some important basins like Serenitatis to pre-Nectarian time, were generally consistent with those previously derived. Based on this stratigraphy, at least 11 large basins formed in the time between Nectaris and Imbrium. The absolute age of Nectaris, therefore, is a crucial marker in the lunar time-stratigraphic sequence for understanding the impact flux on the Moon, and by extension, the entire inner solar system. For several decades, workers have attempted to constrain the age of the Nectaris basin through radiometric dating of lunar samples. However, there is little agreement on which samples in our collection represent Nectaris, if any, and what the correct radiometric age of such samples is. The importance of the age of Nectaris goes far beyond assigning a stratigraphic marker to lunar chronology. Several dynamical models use Nectaris as their pin date, so that this date becomes crucial in understanding the time-correlated effects in the rest of the solar system. The importance of the Nectaris basin age, coupled with its nearside, mid-latitude location, make remnants of the impact-melt sheet an attractive target for a future mission, either for in-situ dating or for sample return. We have started exploring this possibility. We have begun a consortium data-analysis effort bringing multiple datasets and analysis methods to bear on these putative impact-melt deposits to characterize their extent, elemental composition and mineralogy, maturity and geologic setting, and to identify potential landing sites that meet both operational safety and science requirements.

Nectaris Basin↗

NASA NTRS2014

The Miniature Radio Frequency Instruments (Mini-RF) Global Observations of Earth's Moon

Radar provides a unique means to analyze the surface and subsurface physical properties of geologic deposits, including their wavelength-scale roughness, the relative depth of the deposits, and some limited compositional information. The NASA Lunar Reconnaissance Orbiter's (LRO) Miniature Radio Frequency (Mini-RF) instrument has enabled these analyses on the Moon at a global scale. Mini-RF has accumulated 67% coverage of the lunar surface in S-band (12.6 cm) radar with a resolution of 30 m/pixel. Here we present new Mini-RF global orthorectified uncontrolled S-band maps of the Moon and use them for analysis of lunar surface physical properties. Reported here are readily apparent global- and regional-scale differences in lunar surface physical properties that suggest three distinct terranes, namely: a (1) Nearside Radar Dark Region; (2) Orientale basin and continuous ejecta; and the (3) Highlands Radar Bright Region. Integrating these observations with new data from LRO's Diviner Radiometer rock abundance maps, as well Clementine and Lunar Prospector derived compositional values show multiple distinct lunar surface terranes and sub-terranes based upon both physical and compositional surface properties. Previous geochemical investigations of the Moon suggested its crust is best divided into three to four basic crustal provinces or terranes (Feldspathic Highlands Terrane (-An and -Outer), Procellarum KREEP Terrane, and South Pole Aitken Terrane) that are distinct from one another. However, integration of these geochemical data sets with new geophysical data sets allows us to refine these terranes. The result shows a more complex view of these same crustal provinces and provides valuable scientific and hazard perspectives for future targeted human and robotic exploration.

Radar observations↗

NASA NTRS2013

Evidence for Water Ice on the Moon: Results for Anomalous Polar Craters from the LRO Mini-RF Imaging Radar

The Mini-RF radar instrument on the Lunar Reconnaissance Orbiter spacecraft mapped both lunar poles in two different RF wavelengths (complete mapping at 12.6 cm S-band and partial mapping at 4.2 cm X-band) in two look directions, removing much of the ambiguity of previous Earth- and spacecraft-based radar mapping of the Moon's polar regions. The poles are typical highland terrain, showing expected values of radar cross section (albedo) and circular polarization ratio (CPR). Most fresh craters display high values of CPR in and outside the crater rim; the pattern of these CPR distributions is consistent with high levels of wavelength-scale surface roughness associated with the presence of block fields, impact melt flows, and fallback breccia. A different class of polar crater exhibits high CPR only in their interiors, interiors that are both permanently dark and very cold (less than 100 K). Application of scattering models developed previously suggests that these anomalously high-CPR deposits exhibit behavior consistent with the presence of water ice. If this interpretation is correct, then both poles may contain several hundred million tons of water in the form of relatively "clean" ice, all within the upper couple of meters of the lunar surface. The existence of significant water ice deposits enables both long-term human habitation of the Moon and the creation of a permanent cislunar space transportation system based upon the harvest and use of lunar propellant.

Mini-RF radar↗

NASA NTRS2012

Radar Scattering and Block Size Properties of Lunar Crater Ejecta From Mini-RF and LROC NAC Data

A major objective of the Mini-RF experiment is to distinguish lunar surfaces that may contain water/ice deposits [1,2]. Better understanding of the backscattering properties of craters of varying age and size is crucial for interpreting data received from the Mini-RF. The Mini-RF transmits a circularly polarized RF electromagnetic energy and coherently receives orthogonal linear polarization echoes [1]. The Mini- RF maps in two separate bands ( =12.6 and 4.5 cm) at a high resolution mode of 30 m/pixel [1]. Given the variables mentioned, the four stokes parameters are reconstructed. The Circular Polarization Ratio (CPR) is calculated for the purposes of understanding subsurface and surface roughness. The CPR is determined from reflections acquired from the ratio of power of the transmitted radio wave in same sense to the reflected radio wave in the opposite sense [1]. Ice in the permanently shadowed regions (PSRs) would be transparent to radar, but the inclusions of materials and imperfections would cause the radio wave to reflect multiple times [3], enhancing the number of same sense reflections and increasing the CPR. In addition, ice also displays the coherent backscatter opposition effect (CBOE), an interferrometric addition of same sense backscatter that further increases the CPR of ice targets [7]. High CPR values also correlate to multiple reflections and are typically associated with very rough surfaces [3]. The average dry lunar surface has a CPR in the range of 0.2-0.4 at 48deg incidence [3]. The purpose of this study is to begin to quantify degrees of surface wavelength-scale roughness with CPR and to understand how such surface roughness is created and gradually destroyed by erosion on the lunar surface. Another goal is to identify and isolate the possible causes of high CPR within the shadowed areas of anomalous polar craters [3]. All the studied craters are non-polar, so that we can see into their interiors in NAC images. The idea is to understand what controls blockiness in these craters so that we can rule out rocks (and rule in ice) for the anomalous polar dark ones [3].

Spudis, P. D.↗

NASA NTRS2012

Inferred Lunar Boulder Distributions at Decimeter Scales

Block size distributions of impact deposits on the Moon are diagnostic of the impact process and environmental effects, such as target lithology and weathering. Block size distributions are also important factors in trafficability, habitability, and possibly the identification of indigenous resources. Lunar block sizes have been investigated for many years for many purposes [e.g., 1-3]. An unresolved issue is the extent to which lunar block size distributions can be extrapolated to scales smaller than limits of resolution of direct measurement. This would seem to be a straightforward statistical application, but it is complicated by two issues. First, the cumulative size frequency distribution of observable boulders rolls over due to resolution limitations at the small end. Second, statistical regression provides the best fit only around the centroid of the data [4]. Confidence and prediction limits splay away from the best fit at the endpoints resulting in inferences in the boulder density at the CPR scale that can differ by many orders of magnitude [4]. These issues were originally investigated by Cintala and McBride [2] using Surveyor data. The objective of this study was to determine whether the measured block size distributions from Lunar Reconnaissance Orbiter Camera - Narrow Angle Camera (LROC-NAC) images (m-scale resolution) can be used to infer the block size distribution at length scales comparable to Mini-RF Circular Polarization Ratio (CPR) scales, nominally taken as 10 cm. This would set the stage for assessing correlations of inferred block size distributions with CPR returns [6].

Baloga, S. M.↗

NASA NTRS2005

Earth-Moon Impacts at ~300 Ma and ~500 Ma Ago

Impact events have played an important role in the evolution of planets and small bodies in the Solar System. Meteorites, lunar melt rocks, and lunar impact glasses provide important information about the geology of the parent body and the age of the impacting episodes. Over 2400 impact glasses from 4 Apollo regolith samples have been geochemically analyzed and a subset has been dated by the (40)Ar/(39)Ar method. New results, consistent with 2 break-ups in the Asteroid Belt, are presented here. Our previous study reported that (40)Ar/(39)Ar ages from 9 impact glasses showed that the Moon experienced significant impacts at approx. 800 Ma and at approx. 3800 Ma ago, somewhere in the vicinity of the Apollo 16 landing site. Additionally, reported on Apollo 12 samples with ages around 800 Ma, together implying global bombardment events. New data on 7 glasses from regolith sample 66041,127 show that the Moon also experienced impact events at approx. 300 Ma and > 500 Ma ago, which may coincide with the break-ups in the Asteroid Belt of the L- and H-chrondrite parent bodies. Since meteoritic evidence for these breakups has been found on Earth, it follows that evidence should be found in lunar samples as well. Additional information is included in the original extended abstract.

Zellner, N. E. B.↗

NASA NTRS2003

Geochemistry and Impact History at the Apollo 16 Landing Site

Lunar impact glasses possess the unmodified refractory element ratios of the original fused target materials at the sites of impacts. These target materials are usually regolith. 866 glasses from the Apollo 16 landing site have been analyzed by electron microprobe in this study. These glasses show significant variation and hint at the existence of highland basalt (HB) regolith compositions atypical of the usual HB compositions historically found at the Apollo 16 site. Additionally, a large number of mare glasses have been identified. Clementine color image data have been used to construct iron, titanium, and aluminum maps for comparison with the sample database. These maps suggest that the Apollo 16 landing site is largely composed of anorthositic material and that mare compositions are not found close by. Nine of these impact glasses have been dated by the Ar-40/Ar-39 technique and may be used to constrain the impact history at the Apollo 16 landing site. These results illustrate how lunar impact glasses together with orbital data can provide geochemical constraints on the local and regional geology of the Moon.

Zellner, N. E. B.↗

NASA NTRS2002

Apollo 14 Impact Glasses and Clementine Data: Implications for Regional Geology

Clementine color image data and analyses of 778 lunar impact glasses have been used together to suggest that the highlands of the Fra Mauro region consist of a KREEP-rich regolith overlying a feldspathic terrain. Low-KREEP impact glasses may possess a memory of impacts prior to 3.9 Ga ago. Additional information is contained in the original extended abstract.

Zellner, N. E. B.↗

NASA NTRS2002

Lunar Topography and Basins Mapped Using a Clementine Stereo Digital Elevation Model

Planet-wide (1 km/pixel and 5 km/pixel) Digital Elevation Models (DEM) of the Moon have been produced using Clementine UVVIS (Ultraviolet-Visible) stereo. Six new basins have been discovered, two suspected basins have been confirmed, and the dimensions of existing basins better defined. Additional information is contained in the original extended abstract.

Cook, A. C.↗

NASA NTRS1995

A Spectral Survey of the Crisium Basin Region of the Moon

The Crisium basin region harbors a number of interesting features, including geochemical and radar anomalies, light plains units and possible hidden mare deposits (cryptomaria). This report presents preliminary results of a telescopic near-infrared spectral study concerning a variety of surface units in the Crisium region. Observations were made of Mare Crisium, light plains deposits north of Taruntius crater, and the terra associated with the Crisium basin.

Blewett, D. T.↗

NASA NTRS1995

Emplacement of Xenolith Nodules in the Kaupulehu Lava Flow, Hualalai Volcano, Hawaii

The basaltic Kaupulehu 1800-1801 lava flow of Hualalai Volcano, Hawaii contains abundant ultramafic xenoliths. Many of these xenoliths occur as bedded layers of semi-rounded nodules, each thinly coated with a veneer (typically 1 mm thick) of lava. The nodule beds are analogous to cobble deposits of fluvial sedimentary systems. Although several mechanisms have been proposed for the formation of the nodule beds, it was found that, at more than one locality, the nodule beds are overbank levee deposits. The geological occurrence of the nodules, certain diagnostic aspects of the flow morphology and consideration of the inferred emplacement process indicate that the Kaupulehu flow had an exceptionally low viscosity on eruption and that the flow of the lava stream was extremely rapid, with flow velocities of at least 10 m/s (more than 40 km/h. This flow is the youngest on Hualalai Volcano and future eruptions of a similar type would pose considerable hazard to life as well as property.

Guest, J. E.↗

NASA NTRS1994

The Clementine mission: Initial results from lunar mapping

Clementine was a mission designed to test the space worthiness of a variety of advanced sensors for use on military surveillance satellites while, at the same time, gathering useful scientific information on the composition and structure of the Moon and a near Earth asteroid. Clementine was dispatched for an extended stay in the vicinity of Earth's Moon on 25 Jan. 1994 and arrived at the Moon on 20 Feb. 1994. The spacecraft started systematic mapping on 26 Feb., completed mapping on 22 Apr., and left lunar orbit on 3 May. The entire Clementine project, from conception through end of mission, lasted approximately three years. Topographic profiles derived from lidar laser altimetry permitted construction of a global topographic map of the Moon. Clementine also aimed at mapping the color of the Moon in eleven different wavelengths in the visible and near infrared parts of the system. With rock and soil samples of known geological context available from the Apollo and Lunar programs, the Clementine mission offers the data needed to construct a global digital image model of the Moon.

Spudis, P. D.↗

NASA NTRS1994

The Clementine Mission: Initial Results from lunar mapping

Clementine was a mission designed to test the space-worthiness of a variety of advanced sensors for use on military surveillance satellites while, at the same time, gathering useful scientific information on the composition and structure of the Moon and a near-Earth asteroid. Conducted jointly by the Ballistic Missile Defense Organization (BMDO, formerly the Strategic Defense Initiative Organization) of the US Department of Defense and NASA, Clementine was dispatched for an extended stay in the vicinity of Earth's moon on 25 January 1994 and arrived at the Moon on 20 February 1994. The spacecraft started systematic mapping on 26 February, completed mapping on 22 April, and left lunar orbit on 3 May. The entire Clementine project, from conception through end-of-mission, lasted approximately 3 years.

Spudis, P. D.↗

NASA NTRS1993

Spectral and multispectral imaging studies of lunar mantled mare deposits

Near-IR reflectance spectra (0.6-2.5 microns) and CCD images in the extended visible range (0.4-1.0 microns) obtained with Earth-based telescopes have been used to investigate the composition and origin of formations in the Schiller-Schickard region of the Moon. Of particular interest are the Schickard light plains, which represent an area of mantled mare basalt, or cryptomare. Here local pre-existing mare basalts were eroded and incorporated into a highlands-rich deposit by eject a from the Orientale Basin. Spectra observations of mature and immature highland and mare surfaces, as well as dark-halo crater materials provide information on the mafic mineralogy of features in the area. Analyses of the '1 micron' absorption band and spectral mixing models indicate that selected spots in the light plains contain on the order of 50 percent mare basalt. CCD image cubes can be used to map the amount of basalt in the light plains and evaluate changes with radial distance from Orientale.

Blewett, D. T.↗

NASA NTRS1993

Spectral reflectance studies of the Humorum Basin region

A portion of the mare-bounding (MB) ring of Humorum Basin is composed of pure anorthosite while other parts of the ring are composed of noritic anorthosite. An episode of mare volcanism emplaced basaltic units in the region northwest of the MB ring after the Humorum impact event. Subsequently, large impacts emplaced a veneer of highlands material atop the basalt flows. Some mare material could have been mixed with this highlands debris either by local mixing by secondary craters or by vertical mixing. Spectra for most other highlands units in the region indicate a noritic anorthosite lithology. Spectra of mare basalts in Mare Humorum and nearby mare flooded craters show relatively deep absorption bands due to the presence of abundant high-Ca pyroxene. An analysis of spectra for a small number of craters in the highlands west of the outer ring of Humorum reveals the presence of high-Ca pyroxene. This suggests the possible presence of an extensive gabbroic province.

Peterson, C. A.↗

NASA NTRS1992

Workshop on Geology of the Apollo 17 Landing Site

The topics covered include the following: petrology, lithology, lunar rocks, lunar soil, geochemistry, lunar geology, lunar resources, oxygen production, ilmenite, volcanism, highlands, lunar maria, massifs, impact melts, breccias, lunar crust, Taurus-Littrow, minerals, site selection, regolith, glasses, geomorphology, basalts, tectonics, planetary evolution, anorthosite, titanium oxides, chemical composition, and the Sudbury-Serenitatis analogy.

Ryder, G.↗

NASA NTRS1992

A spectral survey of the Serenitatis Basin region of the Moon

In recent years, we have utilized the Apollo orbital geochemistry datasets and Earth-based spectral reflectance data to investigate the composition of highland units associated with lunar multiring basins. These include Imbrium, Orientale, and Nectaris Basins. We have also analyzed a large number of near-IR reflectance spectra and multispectral images in an attempt to answer a variety of questions concerning the Serenitatis Basin. These questions include the following: (1) What is the composition of highland units in the region and how do these compositions vary as a function of position around and distance from Serenitatis?; (2) What was the crustal stratigraphy of the Serenitatis preimpact target site?; (3) How do the Apollo 17 samples relate to geologic units in the surrounding highlands?; (4) What is the nature and origin of light plains deposits in the region?; and (5) Do cryptomare occur in the Serenitatis region? The purpose of this paper is to present the preliminary results of our analyses of spectral data obtained for the Serenitatis Basin region.

Hawke, B. R.↗