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Cintala, M. J.

Publications and source records attributed to Cintala, M. J..

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Impact cratering in low-gravity environments - Results of reconnaissance experimentation on the NASA KC-135A reduced-gravity aircraft

A program of flight experimentation was performed on the NASA KC-135A reduced-gravity aircraft to evaluate the potential for conducting impact experiments in reduced-gravity environments and to collect impact-cratering data at gravity levels below 1 g. Lead pellets were launched into coarse-grained sand at velocities of about 65-130 m/sec while the gravitational acceleration was maintained at 0.59-0.05 g. A total of 64 craters were studied and, after allowance is made for the atmospheric pressure over the target (0.83 atm), their diameters are found to have been consistent with scaling predictions made on the basis of ground-based experimentation. Formation times were also obtained for 33 of these craters and constitute a distribution that is somewhat different from that described by the ground-based data. Nevertheless, the KC-135 data set as a whole falls on the trend formed by the ground-based results. The overall agreement between the two data sets attests to the stability of the aircraft as a platform for impact experimentation.

Cintala, M. J.↗
NASA NTRS1986

Small-scale impacts into rock - An evaluation of the effects of target temperature on experimental results

A series of cratering and catastrophic fragmentation experiments has been performed, involving the impact of aluminum and stainless-steel spheres into warm (about 298 K) and cold (about 100 K) granodiorite targets. Although some vague hints of a thermal effect might be found in some of the results, in no case was there a substantial difference between the warm and cold series. Since these experiments were well within the strength-dominated regime of impact phenomena, variations due to low target temperatures in more energetic events will probably be negligible. Thus, there appear to be no significant temperature-dependent mechanical effects during impact into solid rock over a wide range of temperatures prevalent in the solar system.

Smrekar, S.↗
NASA NTRS1986

Low-gravity impact experiments: Progress toward a facility definition

Innumerable efforts were made to understand the cratering process and its ramifications in terms of planetary observations, during which the role of gravity has often come into question. Well known facilities and experiments both were devoted in many cases to unraveling the contribution of gravitational acceleration to cratering mechanisms. Included among these are the explosion experiments in low gravity aircraft, the drop platform experiments, and the high gravity centrifuge experiments. Considerable insight into the effects of gravity was gained. Most investigations were confined to terrestrial laboratories. It is in this light that the Space Station is being examined as a vehicle with the potential to support otherwise impractical impact experiments. The results of studies performed by members of the planetary cratering community are summarized.

Cintala, M. J.↗
NASA NTRS1986

Hypervelocity particle capture: Some considerations regarding suitable target media

Hypervelocity particles colliding with passive capture media will be traversed by shock waves; depending on the stress amplitude, the particle may remain solid or it may melt or vaporize. Any capture mechanism considered for cosmic dust collection in low Earth-orbit must be designed such that sample alteration and hence loss of scientific information is minimized. Capture of pristine particles is fundamentally difficult, because the specific heat of melting and even vaporization is exceeded upon impact at typical, geocentric encounter velocities. From the results of calculated and observed melting behaviors it is concluded that shock stresses in excess of 50 GPA should be avoided during hypervelocity particle capture on board Space Station and that stresses 20 GPa, even at 15 km/s collision velocities, should constitute desirable instrument design goals. Some principal characteristics of the capture medium that may satisfy these requirements are identified.

Horz, F.↗
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

Grain size evolution and fractionation trends in an experimental regolith

The communication of blocky planetary surfaces into fine-grained regoliths was simulated by impacting a fragmental gabbro target 200 times with stainless steel projectiles. It is found that the comminution efficiency of the surfaces changes with time, being highest in the early stages of regolith formation and decreasing gradually. The relationship between mean grain size and cumulative energy is not linear. Individual, fine-grained regolith components can be generated very early from relatively large progenitor fragments without going through intermediate-size fractions. Impact comminution is capable of producing fractionated fines as postulated by Papike et al. (1982). The role of grain-size selective, lateral transport to explain the fractionated nature of lunar regolith fines may have been overestimated in the past.

Horz, F.↗
NASA NTRS1981

Meteoroid impact into short-period comet nuclei

The effects of extended meteoroid bombardment on short-period comet nuclei are examined and their possible implications for asteroid and meteorite studies are discussed. It is suggested that after devolatilization of the nucleus, the accumulated material might combine with primary cometary solids to produce environments conducive to the formation of polymict brecciated meteorites and to influence reflectance spectra of the asteroids. Such meteoroids removed from active nuclei during degassing could be placed in trajectories that might evolve into earth-crossing orbits.

Cintala, M. J.↗
NASA NTRS1980

Martian fresh crater depths - More evidence for subsurface volatiles

The paper presents and examines new depth data, which have greater accuracy and area coverage than those acquired previously, for fresh Martian craters through shadow measurements on high quality Viking Orbiter photography. Consideration is given to these data in the context of similar measurements of lunar and Mercurian craters, noting that most craters studied are shallower than those on the Moon and Mercury. Finally, processes are described which could account for the observed interior morphometries.

Cintala, M. J.↗
NASA NTRS1979

Emplacement of Fahrenheit crater ejecta at the Luna-24 site

The likelihood that the gabbroic and monomineralic fragments in the Luna-24 soils were excavated during the Fahrenheit cratering event can be assessed by considering the quantity, characteristics, and mode of deposition of Fahrenheit ejecta in the vicinity of the Luna-24 site. The original morphology of Fahrenheit's ejecta deposits is inferred by examining a fresh crater, Lichtenberg B, of a comparable site that formed in a similar type of target material. On the basis of this analogy, a probability of over 80% was calculated that the Luna-24 site was morphologically disturbed by the deposition of Fahrenheit ejecta. The relative abundance, gabbroic composition, and unshocked character of the holocrystalline fragments discovered in the Luna-24 core sample are consistent with the widespread occurrence of Fahrenheit deposits and the characteristics of Fahrenheit ejecta anticipated at the Luna-24 range.

Settle, M.↗
NASA NTRS1979

Mercurian crater rim heights and some interplanetary comparisons

Rim height (Re) data have been gathered through shadow measurements for 30 fresh mercurian craters with diameters (D) between 2.6 and 39 km. Small mercurian craters (i.e., those less than about 16 km in diameter) have higher rims than do lunar craters of the same diameter; on the basis of Re/D measurements alone, however, mercurian craters larger than about 16 km appear to be indistinguishable from their lunar counterparts (those greater than about 21 km in diameter). Apparent crater depths (Ra, the crater depth measured from the initial target surface) derived from empirical data allude to a decrease in Ra/D with calculated modal impact velocity. This is consistent with the hypothesis that higher impact velocities place the effective depth of burst of the event closer to the surface, thus causing a shallower crater.

Cintala, M. J.↗
NASA NTRS1979

The nature and effects of impact cratering on small bodies

Collisions between asteroids and other forms of solar system debris are discussed, especially relatively high-energy, non-catastrophic collisions, the resulting craters, and the effects they should have on the surfaces and interiors of target bodies. Attention is given to the nature and formation of impact craters, as well as to shock waves and the energy (kinetic, internal) imparted through them, crater scaling, stress wave-surface interactions, impact melt, and the effects of non-escaping ejecta on the surface of the target body (rock, fine-grained regolith, porous media).

Cintala, M. J.↗
NASA NTRS1978

Interior morphology of fresh Martian craters - The effects of target characteristics

The interior morphology of 183 fresh Martian craters observed on Viking imagery was studied. Freshness was determined by rim sharpness and continuity according to the scheme used to classify lunar and Mercurian craters. Results indicate that central-peak and wall degradation features are more common than previously thought. Central peaks are observed in craters as small as 2 km in diameter and in nearly all fresh craters with diameters greater than 10 km. Scallops or terraces are found to occur in all craters with diameters greater than 20 km, and wall slumping seems common in craters from 5 to 10 km in diameter. The ratio of crater diameter to crater floor diameter is significantly larger than for lunar craters. Central peaks and pits are more frequent in craters formed in cratered terrain than in those formed on plains; wall failure occurs at smaller diameters in plains craters. It is suggested that these peculiarities of crater interior morphologies may be due to a subsurface volatile layer. The influence of target variations on the interior morphologies observed in fresh craters was studied. Preliminary results indicate well-defined effects due to target differences.

Wood, C. A.↗
NASA NTRS1978

Characteristics of the cratering process on small satellites and asteroids

Photographs of the two known natural satellites of Mars - Phobos and Deimos - illustrate the importance of impact cratering in the postformational histories of the two moons and, by inference, the asteroids and other small planetary satellites. The objectives of the present study are to investigate qualitatively the impact cratering process on small bodies, to apply some of these considerations to the observed surfaces of Phobos and Deimos, and to consider the asteroids briefly in the light of these results. The cratering process on small bodies is discussed in three stages: compression, excavation, and modification. Nonescaping and escaping ejecta are considered.

Cintala, M. J.↗
NASA NTRS1977

The effects of target characteristics on fresh crater morphology - Preliminary results for the moon and Mercury

The results are reported of an analysis of the characteristics of fresh crater samples occurring on the two major geologic units on the moon (maria and highlands) and on Mercury (smooth plains and cratered terrain). In particular, the onset diameters and abundances of central peaks and terraces are examined and compared for both geologic units on each planet in order to detect any variations that might be due to geologic unit characteristics. The analysis of lunar crater characteristics is based on information provided in the LPL Catalog of Lunar Craters of Wood and Andersson (1977). The Mercurian data set utilized is related to a program involving the cataloguing of Mercurian craters visible in Mariner 10 photography. It is concluded that the characteristics of the substrate have exerted a measurable influence on the occurrence of central peaks, terraces, and scallops in flash crater samples. Therefore, in order to compare the morphologic characteristics of fresh crater populations between planets, an analysis of possible substrate-related differences must first be undertaken for each planet under consideration. It is suggested that large variations in gravity do not produce major variations in crater wall failure.

Cintala, M. J.↗
NASA NTRS1977

Crater degradation on Mercury and the moon - Clues to surface evolution

A preliminary investigation was conducted regarding the variations in the morphological characteristics of Mercurian craters that appear to be associated with a degradation of fresh craters. Craters are classified according to relative states of degradation in order to provide evidence on degradation styles and rates on Mercury, and to correlate degradation with major geologic events in the history of the planet. Processes and relative rates of degradation on Mercury and the moon are also compared. Degradation trends of crater morphology are found to be parallel on Mercury and the moon. The severe destruction of interior structures in lunar craters may have resulted from more widespread distribution of ejecta due to the moon's lower gravity. The possibility is considered that the smooth plains on the surface of Mercury were formed early in the history of that planet.

Wood, C. A.↗
NASA NTRS1977

Martian fresh crater morphology and morphometry - A pre-Viking review

A brief review of Martian crater data is presented and a short summary is provided of Martian fresh crater morphology and morphometry based on pre-Viking information. The pre-Viking Mars missions are considered, taking into account the flyby of Mariner 4 in July 1965, the flyby of Mariner 6 in July 1969, the flyby of Mariner 7 in August 1969, and the insertion of Mariner 9 into a Martian orbit in November 1971. The 7329 photographs of the planet and its moons transmitted by Mariner 9 to earth provide a substantial basis for formulating a large body of data on crater morphometry, morphology, and location. In general, fresh Martian crater morphology follows a diameter-dependent progression. The simplest morphology is found in the smallest craters. The morphology remains essentially constant through diameters of approximately 10 km. Morphologies rapidly become more complex in the diameter range of 10-40 km.

Cintala, M. J.↗