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At least 19 records

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NASA NTRS1988

Crater identification and resolution of lunar radar images

The relations between the identification of dominant lunar landforms, craters, and radar images at three resolutions are investigated. Although the percentage of craters that can be identified is found to increase with diameter or relief for any given resolution, it is noted that craters have not been identified at all diameters and relief. It is shown that the relation between the percentage of identified craters and their dimensions depends on the size-frequency distributions of both diameters and relief, and that crater identification depends strongly on the resolution of the radar image.

Moore, H. J.↗

NASA NTRS1989

Crater identification and resolution of lunar radar images

Moore, H. J.↗

NASA NTRS2010

Crater Identification Algorithm for the Lost in Low Lunar Orbit Scenario

Recent emphasis by NASA on returning astronauts to the Moon has placed attention on the subject of lunar surface feature tracking. Although many algorithms have been proposed for lunar surface feature tracking navigation, much less attention has been paid to the issue of navigational state initialization from lunar craters in a lost in low lunar orbit (LLO) scenario. That is, a scenario in which lunar surface feature tracking must begin, but current navigation state knowledge is either unavailable or too poor to initiate a tracking algorithm. The situation is analogous to the lost in space scenario for star trackers. A new crater identification algorithm is developed herein that allows for navigation state initialization from as few as one image of the lunar surface with no a priori state knowledge. The algorithm takes as inputs the locations and diameters of craters that have been detected in an image, and uses the information to match the craters to entries in the USGS lunar crater catalog via non-dimensional crater triangle parameters. Due to the large number of uncataloged craters that exist on the lunar surface, a probability-based check was developed to reject false identifications. The algorithm was tested on craters detected in four revolutions of Apollo 16 LLO images, and shown to perform well.

Hanak, Chad↗

NASA NTRS1977

Rochechouart meteorite crater - Identification of projectile

Ten samples from the 20-km Rochechouart crater in France have been analyzed for the siderophile elements Ir, Os, Re, Au, Pd, Ni, and Ge by radiochemical neutron activation analysis. The up to 1000-fold enrichment of siderophiles correlates with shock effects, increasing in the following order from least to greatest: basement rocks, glass-free breccias, glassy breccias, impact melts. The abundance pattern of the meteorite was determined from interelement correlations. Several samples fell off the correlation lines, presumably due to recrystallization and weathering of impact glasses during the approximately 165-m.y. age of the crater. The most reliable diagnostic elements were Os, Ir, Ni, and Pd; their abundance ratios suggest that the Rochechouart meteorite was a IIA iron.

Janssens, M.-J.↗

NASA NTRSDate not supplied

Machine Learning Based Crater Detection for Terrain Relative Navigation

As Lunar exploration continues to become more commonplace, reliable methods of precise Terrain Relative Navigation (TRN) are needed. While there are many TRN techniques available, one that has received increased interest in the past few years is that of crater based navigation. Crater based navigation has numerous benefits, including being a human recognizable feature (important for crewed missions), as well as the fact that craters are often possible hazards that need to be detected and avoided. The use of crater based navigation has been limited however. This has been due to the difficulty of running such algorithms on board a spacecraft, as well as the difficulty in procuring large amounts of the required training data. This paper presents a new rendering tool for generating large amounts of high quality training data. It then looks at two recently developed machine learning techniques for crater detection and crater identification in real-time on near-future space hardware.

computer vision↗

NASA NTRS1972

Artificial lunar impact craters: Four new identifications, part I

The Apollo 16 panoramic camera photographed the impact locations of the Ranger 7 and 9 spacecraft and the S-4B stage of the Apollo 14 Saturn launch vehicle. Identification of the Ranger craters was very simple because each photographed its target point before impact. Identification of the S-4B impact crater proved to be a simple matter because the impact location, as derived from earth-based tracking, displayed a prominent and unique system of mixed light and dark rays. By using the criterion of a dark ray pattern, a reexamination of the Apollo 14 500 mm Hasselblad sequence taken of the Apollo 13 S-4B impact area was made. This examination quickly led to the discovery of the ray system and the impact crater. The study of artificial lunar impact craters, ejecta blankets, and ray systems provides the long-needed link between the various experimental terrestrial impact and explosion craters, and the naturally occurring impact craters on the moon. This elementary study shows that lunar impact crater diameters are closely predictable from a knowledge of the energies involved, at least in the size range considered, and suggests that parameters, such as velocity, may have a profound effect on crater morphology and ejecta blanket albedo.

Whitaker, E. A.↗

NASA NTRS2011

Identification of Impact Craters in Foils from the Stardust Interstellar Dust Collector

The Stardust Interstellar Dust Collection tray provides the first opportunity for the direct laboratory-based measurement of contemporary interstellar dust. The total exposed surface of the tray was approximately 0.1 square meters, including 153 square centimeters of Al foil in addition to the silica aerogel tiles that are the primary collection medium. Preliminary examination of aerogel tiles has already revealed 16 tracks from particle impacts with an orientation consistent with an interstellar origin, and to date four of the particles associated with these tracks have a composition consistent with an extraterrestrial origin. Tentative identification of impact craters on three foil samples was also reported previously. Here we present the definitive identification of 20 impact craters on five foils.

Stroud, R. M.↗

NASA NTRS2024

Digital Lunar Exploration Sites (DLES) Terrain Crafting

Humans will soon be returning to the surface of the Moon with NASA’s Artemis program. The Artemis program is an international collaboration that will consist of a complex series of space systems and missions to explore the lunar surface and pave the way for the future exploration of Mars. NASA and its partners rely heavily on simulation for lighting and navigation studies as well as training astronauts, flight controllers, and mission support staff. The NASA Exploration Systems Simulations (NExSyS) team in the Simulation and Graphics Branch (ER7) in the Engineering Directorate at NASA’s Johnson Space Center has built up many simulation products to support this effort, one of which is the Digital Lunar Exploration Sites (DLES). DLES is a collection of products used to simulate and render the lunar surface in a digital environment. We discussed and presented an overview of the DLES products at the 2022 IEEE Aerospace Conference in Big Sky, MT with a paper titled "Digital Lunar Exploration Sites". This “DLES Terrain Crafting” paper will expand on the information previously provided in “DLES” paper and dive deeper into the details of the terrain crafting process and the toolsets used to support this task. The best digital data currently available of the lunar surface is provided by the Lunar Reconnaissance Orbiter (LRO). Its Lunar Orbiter Laser Altimeter (LOLA) achieves an impressive resolution of 5m per pixel at the Lunar South Pole (LSP) and can generate datasets covering a large continuous region near the LSP. There are a few additional methods, such as Shape from Shading which can infer higher resolution data (up to 1m per pixel) from the LRO Narrow Angle Camera (NAC) images. However, surface-based simulations require higher-resolution data, and this paper will discuss the process of enhancing the terrain to meet that need. The process begins with capturing statistical data of craters in the regions of interest using images provided by the LRO NAC. This data is then used to scatter artificial features which are not captured in the truth data, resulting in an enhanced DEM with a much higher resolution of 20cm per pixel. Many tools were built up to assist in the creation of these artificial Digital Elevation Models (DEM), which this paper will discuss in detail. DEMs themselves are a very powerful representation of a planetary surface, and many operations and tools can utilize the data they contain. This paper includes a description of the rendering of the lunar surface in a graphics engine, generation of contact patches to simulate tire to ground interaction, and ray tracing utilities to model Line of Sight (LOS) interactions with the terrain. This paper will also explore some new tool sets currently under development which aim to utilize Machine Learning (ML) to assist in the identification of craters from LRO NAC imagery. While this is not a novel idea, the NExSyS team is developing a unique approach which may result in more robust identification of crater characteristics.

Artemis↗

NASA NTRS1989

Radar altimetry of large Martian craters

A total of 108 13-cm wavelength scans conducted for the 23 to -22 deg latitude regions of Mars during the 1971-1982 oppositions are of sufficiently high resolution to allow elevation differences of as much as 3 km over less than 10 deg longitude to be observed; most of this local relief is furnished by structural elements of impact craters. The data set has allowed identification of 152 complex degraded craters, some as small as 25 km diameter. Measured crater depths rarely exceed 2.5 km, and low exterior relief rather than overall low relief seems to be the distinguishing characteristic of large degraded craters. Processes other than fluvial sedimentation appear to have contributed to crater shallowing.

Roth, L. E.↗

NASA NTRS1981

Identification of the projectile at the Brent crater, and further considerations of projectile types at terrestrial craters

An analysis of impact melt samples from a drill hole at the Brent crater in Ontario for siderophile trace elements indicative of meteoritic contamination, has resulted in 823-857 m-deep basalt melt zone samples enriched in Ir, Os, Pd, Ni, Co, Cr and Se over basement. The abundance pattern suggests a chondritic projectile and, from a Ni-Cr correlation of 10 melt samples, an L or LL chondrite is inferred. Data from the Manicouagan, Mitastin, and Zhamanshin craters are also assessed, and large differences in siderophile element concentrations are found among the tektites which otherwise have similar chemical compositions. There are now four known craters formed by chondrites, with Brent being the smallest among them.

Palme, H.↗

NASA NTRS1997

Impact Cratering Calculations

Understanding the physical processes of impact cratering on planetary surfaces and atmospheres as well as collisions of finite-size self-gravitating objects is vitally important to planetary science. The observation has often been made that craters are the most ubiquitous landform on the solid planets and the satellites. The density of craters is used to date surfaces on planets and satellites. For large ringed basin craters (e.g. Chicxulub), the issue of identification of exactly what 'diameter' transient crater is associated with this structure is exemplified by the arguments of Sharpton et al. (1993) versus those of Hildebrand et al. (1995). The size of a transient crater, such as the K/T extinction crater at Yucatan, Mexico, which is thought to be the source of SO,-induced sulfuric acid aerosol that globally acidified surface waters as the result of massive vaporization of CASO, in the target rock, is addressed by our present project. The impact process excavates samples of planetary interiors. The degree to which this occurs (e.g. how deeply does excavation occur for a given crater diameter) has been of interest, both with regard to exposing mantle rocks in crater floors, as well as launching samples into space which become part of the terrestrial meteorite collection (e.g. lunar meteorites, SNC's from Mars). Only in the case of the Earth can we test calculations in the laboratory and field. Previous calculations predict, independent of diameter, that the depth of excavation, normalized by crater diameter, is d(sub ex)/D = 0.085 (O'Keefe and Ahrens, 1993). For Comet Shoemaker-Levy 9 (SL9) fragments impacting Jupiter, predicted excavation depths of different gas-rich layers in the atmosphere, were much larger. The trajectory and fate of highly shocked material from a large impact on the Earth, such as the K/T bolide is of interest. Melosh et al. (1990) proposed that the condensed material from the impact upon reentering the Earth's atmosphere induced. radiative heating, and producing global firestorms. The observed reentry splash of the SL-9 impact-induced plumes that reimpact Jupiter (Boslough et al., 1994) supported Melosh's K/T model. The fate of early primitive planetary atmospheres during the latter stages of planetary accretion, resulting from impactors in the 100 to 103 km diameter require modeling, e.g. Newman et al. (1997). Ahrens (1990; 1993) and Chen and Ahrens (1997) found that upon delivery of most of the impact energy to the solid planet, very large ground motions arise, which couple sufficient kinetic energy to the atmosphere to cause substantial atmospheric escape. The trade-off of this model with that of Cameron (1997) who suggests that atmospheric blow-off occurs as a result of the massive impact-induced heating of the atmosphere and Pepin (1997) who uses this heating event to model differential hydrodynamic loss of lighter atmospheric gases, requires further research.

Ahrens, Thomas J.↗

NASA NTRS2003

Autonomous landmark tracking orbit determination strategy

In this paper, an orbit determination strategy is described that is fully autonomous and relies on a computer-based crater detection and identification algorithm that is suitable for both automation of the ground based navigation system and autonomous spacecraft based navigation.

landmark tracking orbit determination↗

NASA NTRS1980

Meteoritic material at four Canadian impact craters

Eleven impact melt and six basement rock samples from four craters were analyzed by neutron activation for Au, Co, Cr, Fe, Ge, Ir, Ni, Os, Pd, Re and Se. Wanapitei Lake, Ontario: the impact melts show uniform enrichments corresponding to 1-2% C1-chondrite material. Interelement ratios (Co/Cr, Ni/Cr, Ni/Ir) suggest that the impacting body was a C1-, C2-, or LL-chondrite. Nicholson Lake, North West Territory: Ni, Cr and Co are distinctly more enriched than Ir and Au which tentatively suggests an olivine-rich achondrite (nakhlite or ureilite). Gow Lake, Saskatchewan and Mistastin, Labrador: small enrichments in Ir and Ni; both the low Ir/Ni ratios and low Cr content suggest iron meteorites, but the signals are too weak for conclusive identification. A tentative comparison of meteoritic signatures at 10 large, greater than or equal to 4 km craters and their presumed celestial counterparts (13 Apollo and Amor asteroids) shows more irons and achondrites among known projectile types, and a preponderance of S-type objects, having no known meteoritic equivalent, among asteroids. It is not yet clear that these differences are significant, in view of the tentative nature of the crater identifications and the limited statistics.

Wolf, R.↗

NASA NTRS2016

Observational Constraints on the Identification of Shallow Lunar Magmatism: Insights from Floor-Fractured Craters

Floor-fractured craters are a class of lunar crater hypothesized to form in response to the emplacement of a shallow magmatic intrusion beneath the crater floor. The emplacement of a shallow magmatic body should result in a positive Bouguer anomaly relative to unaltered complex craters, a signal which is observed for the average Bouguer anomaly interior to the crater walls. We observe the Bouguer anomaly of floor-fractured craters on an individual basis using the unfiltered Bouguer gravity solution from GRAIL and also a degree 100-600 band-filtered Bouguer gravity solution. The low-magnitude of anomalies arising from shallow magmatic intrusions makes identification using unfiltered Bouguer gravity solutions inconclusive. The observed anomalies in the degree 100-600 Bouguer gravity solution are spatially heterogeneous, although there is spatial correlation between volcanic surface morphologies and positive Bouguer anomalies. We interpret these observations to mean that the spatial heterogeneity observed in the Bouguer signal is the result of variable degrees of magmatic degassing within the intrusions.

Jozwiak, L. M.↗

NASA NTRS1972

Astronaut observations from lunar orbit and their geologic significance.

To supplement orbital photography and other remotely sensed data, visual observations were made of 15 lunar surface targets during Apollo mission 15. Among the significant results are (1) characterization of the floor material of Tsiolkovsky as no darker than the average (Eratosthenian) mare material, and interpretration of the lineated unit on the crater rim as a rock avalanche; (2) identification of layers on the wall of the crater Picard, which is probably volcanic in origin, (3) explanation of the ray-excluded zone of the crater Proclus as the result of structurally controlled ray shadowing; (4) observation of cinder cones in the Littrow area with dark haloes that probably are composed of pyroclastic deposits; and (5) recognition that the termini of numerous sinuous rilles in Oceanus Procellarum are flooded with younger mare materials that may have covered older terminal deposits.

El-Baz, F.↗

NASA NTRS1993

U-Pb provenance ages of shocked zircons from the K-T boundary, Raton Basin, Colorado

U-Pb isotopic systematics from analyses of single zircons identify at least two provenance ages, approximately 575 Ma and approximately 330 Ma, for zircons from the impact layer of the K-T boundary, Raton Basin, Colorado. These data are a preliminary confirmation of results reported from the same layer. The zircon provenance ages provide a unique signature for identification of the source crater since igneous rocks of these ages (or sedimentary rocks derived from them) must characterize part of the impact stratigraphy.

Premo, W. R.↗

NASA NTRS1992

Martian parent craters for the SNC meteorites

Information on the petrology and ages of the SNC meteorites, together with geological data derived from Viking Orbiter images, are used to identify 25 candidate impact craters in the Tharsis region of Mars that could possibly be the source craters for these meteorites. The craters chosen as candidate source craters had diameters greater than 10 km, morphologies indicative of young craters, and satisfied both the petrological criteria of the SNCs and the proposed 1.3 Ga crystallization ages. On the basis of the constraints implied by the identification of the candidate source craters, interpretations of the absolute chronology of Mars are proposed.

Mouginis-Mark, P. J.↗

NASA NTRS1974

Identification characteristics of certain lunar relief forms on pictures obtained from spacecraft

This investigation was restricted to the determination of recognitional characteristics of a single type of relief form, dimple craters on the surface of maria. These craters were arbitrarily considered as closed, negative relief forms, circular in plan-view, and symmetric relative to the center. Two techniques were used to determine the shadow configuration in the craters: (1) experimental determination of the shadow edge by illuminating the models of different profile shapes with a parallel light beam; and (2) geometric construction of the shadow edge using a vertical section of the formation in the direction of the solar rays. A morphological map of the surface which includes the following factors can be compiled using the proposed identification technique: crater profile nature, crater diameter, ratio of diameter and depth, sharpness of the lip, and distribution density of the forms.

Kravtsova, V. I.↗