Chuck Simonds - Academia.edu (original) (raw)
Papers by Chuck Simonds
The Space Transportation Nodes Assumptions and Requirements task was performed as part of the Adv... more The Space Transportation Nodes Assumptions and Requirements task was performed as part of the Advanced Space Transportation Support Contract, a NASA Johnson Space Center (JSC) study intended to provide planning for a Lunar Base near the year 2000. The original task statement has been revised to satisfy the following queries: (1) What vehicles are to be processed at the transportation node; (2) What is the flow of activities involved in a vehicle passing through the node; and (3) What node support resources are necessary to support a lunar scenario traffic model composed of a mix of vehicles in an active flight schedule. The Lunar Base Systems Study is concentrating on the initial years of the Phase 2 Lunar Base Scenario. The study will develop the first five years of that phase in order to define the transportation and surface systems (including mass, volumes, power requirements, and designs).
This paper defines the types of technology that would be used in a lunar base for environmental c... more This paper defines the types of technology that would be used in a lunar base for environmental control and life support system and how it might relate to in situ materials utilization (ISMU) for the Space Exploration Initiative (SEI). There are three types of interaction between ISMU and the Environmental Control and Life Support System (ECLSS): (1) ISMU can reduce cost of water, oxygen, and possibly diluent gasses provided to ECLSS--a corollary to this fact is that the availability of indigenous resources can dramatically alter life support technology trade studies; (2) ISMU can use ECLSS waste systems as a source of reductant carbon and hydrogen; and (3) ECLSS and ISMU, as two chemical processing technologies used in spacecraft, can share technology, thereby increasing the impact of technology investments in either area.
The purpose of this study was to perform a first look at the requirements for launch and landing ... more The purpose of this study was to perform a first look at the requirements for launch and landing facilities for early lunar bases and to prepared conceptual designs for some of these facilities. The emphasis of the study is on the facilities needed from the first manned landing until permanent occupancy, the Phase 2 lunar base. Factors including surface characteristics,
Lunar and Planetary Science Conference, Mar 1, 1979
Eos, Transactions American Geophysical Union, 1980
The heavily cratered lunar highlands (see cover) preserve remnants of the moon's origin at 4.... more The heavily cratered lunar highlands (see cover) preserve remnants of the moon's origin at 4.5–4.6 billion years ago and subsequent evolution to 3.8–3.9 billion years ago. Rocks produced during the same time appear to be totally missing from the record on Earth. Thus the lunar highlands afford us the opportunity to study processes that were operative during planetary formation and early evolution; such studies can be expected to yield new insights on the history of the earth and other terrestrial planets during the first few hundred million years of their existence.Studies of the lunar highlands have made great strides since the collection of highland rocks by the Apollo 14,15,16, and 1 7 missions. Many types of information have been interpreted and synthesized, including petrologic and geochemical data collected on highlands samples and photographic and geochemical data, covering large portions of the moon's surface, collected by orbiting spacecraft. Research on igneous pro...
Eos, Transactions American Geophysical Union, 1978
The similarity of the airless intense ly cratered surfaces of Mercury and the moon (Figures la an... more The similarity of the airless intense ly cratered surfaces of Mercury and the moon (Figures la and 1?)) is in striking contrast to the different den sities of the two objects. The similar geologic history inferred from the sur face record is surprising, since the different size and density of these two bodies might suggest different amounts of radiogenic heating, sili cate/metal ratios, and thermal conduc tivity (Figure 2
SAE Technical Paper Series, 1993
ABSTRACT Applied research and technology development (R&TD) is often characterized by unc... more ABSTRACT Applied research and technology development (R&TD) is often characterized by uncertainty, risk, and significant delays before tangible returns are obtained. Given the increased awareness of limitations in resources, effective R&TD today needs a method for up-front assessment of competing technologies to help guide technology investment decisions. Such an assessment approach must account for uncertainties in system performance parameters, mission requirements and architectures, and internal and external events influencing a development program. The methodology known as decision analysis has the potential to address these issues. It was evaluated by performing a case study assessment of alternative carbon dioxide removal technologies for NASA"s proposed First Lunar Outpost program. An approach was developed that accounts for the uncertainties in each technology's cost and performance parameters as well as programmatic uncertainties such as mission architecture. Life cycle cost savings relative to a baseline, adjusted for the cost of money, was used as a figure of merit to evaluate each of the alternative carbon dioxide removal technology candidates. The methodology was found to provide a consistent decision-making strategy for the develpoment of new life support technology. The case study results provided insight that was not possible from more traditional analysis approaches.
SAE Technical Paper Series, 1994
Reviews of Geophysics, 1980
A survey of published descriptions of 32 of the largest, least eroded terrestrial impact structur... more A survey of published descriptions of 32 of the largest, least eroded terrestrial impact structures reveals that the amount of melt at craters in crystalline rocks is approximately 2 orders of magnitude greater than at craters in sedimentary rocks. In this paper we present a model for the impact process and examine whether this difference in melt abundance is due to differences in the amount of melt generated in various target materials or due to differences in the fate of the melt during late stages of the impact. The model consists of a theoretical part for the early stages of impact, based on a Birch‐Murnaghan equation of state, a penetration scheme after Shoemaker (1963), and an attenuation model modified from Gault and Heitowit (1963), and a descriptive part for the later stages of impact, based on field observations at the large terrestrial craters. The impacts of iron, stone, permafrost, and ice meteorites 1 km in diameter into crystalline, carbonate, dry sandstone, ice‐satur...
Physics of The Earth and Planetary Interiors, 1977
Papers are presented outlining various comparisons of Mercury and the moon. Specific topics inclu... more Papers are presented outlining various comparisons of Mercury and the moon. Specific topics include the planetary magnetism and the interiors of the moon and Mercury, the relationship between crustal tectonics and internal evolution, global tectonics, the origin and relative age of lunar and Mercurian intercrater plains, and the relative preservation states of secondary craters. Comparisons are also discussed between lunar
SAE Technical Paper Series, 1991
Space suits and life support equipment will come in intimate contact with Martian soil as aerosol... more Space suits and life support equipment will come in intimate contact with Martian soil as aerosols, wind blown particles and material thrown up by men and equipment on the Martian surface. For purposes of this discussion the soil is assumed to consist of a mixture of cominuted feldspar, pyroxene, olivine, quartz, titanomagnetite and other anhydrous and hydrous iron bearing oxides, clay minerals, scapolite and water soluble chlorides and sulfates. The soil may have photoactivated surfaces that acts as a strong oxidizer with behavior similar to hydrogen peroxide. The existing data about the Mars soil suggests that the dust and sand will require designs analogous to those uses on equipment exposed to salty air and blowing sand and dust. The major design challenges are in developing high performance radiators which can be cleaned after each EVA without degradation, designing seals that are readily cleaned and possibly in selecting materials which will not be degraded by any strong oxida...
Lunar soil may be fabricated into useful building materials analogous to those used for masonry, ... more Lunar soil may be fabricated into useful building materials analogous to those used for masonry, concrete and ceramic pipe applications on earth. The process has been analyzed theoretically and demonstrated on a laboratory scale. Ceramic manufacture can be integrated into the design of equipment to extract H 2 for lunar soil for in situ rocket propellant production.
Journal of Geophysical Research: Solid Earth, 1993
The controversy that raged through the 1950s-1970s over similarities and differences between mete... more The controversy that raged through the 1950s-1970s over similarities and differences between meteorite impact and volcanic processes is revisited in this paper. We propose that there are quantitative similarities in erosion caused by high-speed ejecta produced by either impacts or volcanic processes. Field and petrographic data from the Manicouagan impact crater, Canada, are used to demonstrate that during the emplacement of the impact melt. sheet, erosion occurred at a rate of-•2562 kg m-2 s-1. Field data for the Mount St. Helens lateral blast of May 18, 1980, suggest an erosion rate of 2! kg m-2 s-1 , and field data for a small pyroclastic flow on August 7, 1980, suggest an erosion rate of-•14 kg m-• s-1. It is proposed that these three rates were determined dominantly by the momentum of the ejecta, and a quantitative formulation based on lofting theory is given. A new application of the Monte Carlo approach to analysis provides minimum, most likely, and maximum estimates for both the field and the theoretical analyses. The substantial erosion that occurs by fast moving flows results in mixing of stratigraphic components over large distances and to very fine scales. L. Wilson and coworkers ([•l[•, for example, the review by Wilson et al. [1987]). Larg'e:i:ømputer models now provide insight into dynamic processes. For example, Kieffer [1984] used a Rocketdyne nozzle model to improve calculational accuracy for her proposed model for supersonic flow during the lateral blast at Mount St. He!ens [Kieffer, 1981]. Supercomputer models can now be used to examine the influence of a number of geometric and fluid-dynamical parameters on volcanic eruption processes [Wohletz et al., 1984; Valentine
Journal of Geophysical Research: Solid Earth, 1978
The Rb‐Sr isotopic data for mineral separates from a rock of the Manicouagan impact melt sheet de... more The Rb‐Sr isotopic data for mineral separates from a rock of the Manicouagan impact melt sheet define an isochron of age T = 214 ± 5 (2σ) m.y. and an initial Sr87/sr86 ratio I = 0.70991 ± 0.00007 (2σ). This age is in excellent agreement with the K‐Ar age of 210 ± 8 (2σ) m.y. of Wolfe [1971] and represents the time of crystallization of the melt sheet. Four whole rock samples yield age‐corrected I values ranging from 0.70965 to 0.71006. These high I values are consistent with geological and geochemical arguments that the melt sheet was derived by total melting of Grenville basement rocks during the impact event 214 m.y. ago.
Journal of Geophysical Research, 1978
Calculations for the heat transfer between superheated silicate melt and evenly dispersed I-mm co... more Calculations for the heat transfer between superheated silicate melt and evenly dispersed I-mm cold clasts (a model for impact melt rocks) indicate that (1) most of the thermal gradients are smoothed out in 100 s, (2) the extent to which cold debris is melted is slightly more than proportional to the fractional difference of the equilibration temperature between the solidus and the liquidus of the melt, (3) smaller clasts are preferentially dissolved, (4) the melting of clasts depends on the instantaneous local temperature of the melt in the region of the clasts, and hence clasts can melt during cooling whose liquiduses are higher than the equilibration temperature, and (5) the rate of equilibration is sufficiently high that clasts whose dissolution in the melt is slow may be preserved. Calculations for cooling of the 200-m-thick melt sheet at Manicouagan suggest that complete crystallization takes 35 years at 10 m from the edge and 1600 years at the center. Failure to consider the latent heat of fusion results in estimates of these times which are too short by about a factor of 2. The time to cool to a given temperature is proportional to the square of the distance from the boundary of the melt sheet only when the finite nature of the sheet is unimportant. 1. INTRODUCTION Large meteorite impacts into crystalline igneous and metamorphic rocks on the earth and moon characteristically produce clast-laden impact melt rocks. These rocks, whether from the earth or moon, typically have fine-grained holocrystalline to glassy matrices surrounding up to about 25% mineral clasts 0.1-1.0 mm across and a much smaller volume fraction of lithic fragments ranging in size up to tens of meters. The clasts which are observed for the most part lack the vitrification, planar features, and kink bands characteristic of minerals shocked to pressures over 50 kbar. The specific example discussed here is the 200-m-thick sheet from the 65-km-diameter M anicouagan structure in Quebec. Except for some details, such as the exact thickness of sheet used and the temperature ranges for melting, the calculations are generally applicable to any of the larger terrestrial or lunar craters. The objective of this paper is to model numerically the heat flow both on the scale of the clasts and melt and on the larger scale of loss of heat from the melt sheet as a whole. Such modeling places limits on (1) the time before the viscosity of the melt increases dramatically because the clast-melt thermal interactions trigger nucleation, (2) the temperature of the clasts and melt prior to mixing, and (3) the time scale for crystallization of the melt sheet as a whole. Before the calculations of heat transfer are discussed, it must be emphasized that the processes modeled here take place relatively late in the cratering process, essentially after the excavation has been completed. The cratering process can be divided into a series of steps, as is discussed in a paper in this issue by Simonds et al. [1978] and the papers referenced therein. These steps are as follows: 1. Meteorite collision and passage of compressive shock wave is the first step. To yield the 10 aø ergs estimated for the M anicouagan event, an impact stony meteorite with a typical velocity of' 17 km/s would have to be about 8 km across and take about • s to complete its impact. A compressional shock wave would expand radially outward from the point of impact. The peak shock pressure near the point of impact will be over Copyright ¸ 1978 by the American Geophysical Union.
Journal of Geophysical Research: Solid Earth, 1978
The 65-km-diameter Manicouagan impact structure has an eroded 230-m-thick sheet of clast-laden, i... more The 65-km-diameter Manicouagan impact structure has an eroded 230-m-thick sheet of clast-laden, impact melt rock with an estimated preerosional volume of > 270 km 3. All samples are characterized by mineral and lithic clasts or their incompletely digested remnants. Drawing upon previous theoretical studies of shock waves, we suggest that the Mani6ouagan melt formed in 1 or 2 s in a 5-km-radius hemisphere near the point of impact. The melt accelerated to a few kilometers per second, and the melt and the less shocked debris surrounding it flowed downward and outward for a few minutes until the melt formed a lining of a 5-to 8-km-deep, 15-to 22-km-radius cavity. Extremely turbulent flow thoroughly homogenized the melt and promoted the incorporation and progressive digestion of slower moving, less shocked, cooler debris surrounding the melt. This debris had been finely fragmented, but not melted, to grain sizes of less than 1 mm by the passage of the shock waves. Because of the fine grain size, the melt and fragmented debris equilibrated thermally in about 100 s. During thermal equilibration, virtually all clastic debris (i.e. alkali feldspar, biotite, hornblende, garnet, and scapolite), other than highly refractory quartz and plagioclase as well as many of the centimeter size lithic clasts other than anorthosite, were digested. The preservation of quartz and plagioclase mineral clasts implies that the clasts and melt equilibrated to temperatures near but not above the liquidus. Plagioclase nucleation was initiated by the drop in temperature and possibly by direct nucleation on undigested debris. The initiation of crystallization vastly increased the melt viscosity, preventing settling of 10-mm clasts of basement. Flow of melt through basement fractures is evidence that readjustment of the crater floor took place during the period of clast-melt thermal equilibration.
The Space Transportation Nodes Assumptions and Requirements task was performed as part of the Adv... more The Space Transportation Nodes Assumptions and Requirements task was performed as part of the Advanced Space Transportation Support Contract, a NASA Johnson Space Center (JSC) study intended to provide planning for a Lunar Base near the year 2000. The original task statement has been revised to satisfy the following queries: (1) What vehicles are to be processed at the transportation node; (2) What is the flow of activities involved in a vehicle passing through the node; and (3) What node support resources are necessary to support a lunar scenario traffic model composed of a mix of vehicles in an active flight schedule. The Lunar Base Systems Study is concentrating on the initial years of the Phase 2 Lunar Base Scenario. The study will develop the first five years of that phase in order to define the transportation and surface systems (including mass, volumes, power requirements, and designs).
This paper defines the types of technology that would be used in a lunar base for environmental c... more This paper defines the types of technology that would be used in a lunar base for environmental control and life support system and how it might relate to in situ materials utilization (ISMU) for the Space Exploration Initiative (SEI). There are three types of interaction between ISMU and the Environmental Control and Life Support System (ECLSS): (1) ISMU can reduce cost of water, oxygen, and possibly diluent gasses provided to ECLSS--a corollary to this fact is that the availability of indigenous resources can dramatically alter life support technology trade studies; (2) ISMU can use ECLSS waste systems as a source of reductant carbon and hydrogen; and (3) ECLSS and ISMU, as two chemical processing technologies used in spacecraft, can share technology, thereby increasing the impact of technology investments in either area.
The purpose of this study was to perform a first look at the requirements for launch and landing ... more The purpose of this study was to perform a first look at the requirements for launch and landing facilities for early lunar bases and to prepared conceptual designs for some of these facilities. The emphasis of the study is on the facilities needed from the first manned landing until permanent occupancy, the Phase 2 lunar base. Factors including surface characteristics,
Lunar and Planetary Science Conference, Mar 1, 1979
Eos, Transactions American Geophysical Union, 1980
The heavily cratered lunar highlands (see cover) preserve remnants of the moon's origin at 4.... more The heavily cratered lunar highlands (see cover) preserve remnants of the moon's origin at 4.5–4.6 billion years ago and subsequent evolution to 3.8–3.9 billion years ago. Rocks produced during the same time appear to be totally missing from the record on Earth. Thus the lunar highlands afford us the opportunity to study processes that were operative during planetary formation and early evolution; such studies can be expected to yield new insights on the history of the earth and other terrestrial planets during the first few hundred million years of their existence.Studies of the lunar highlands have made great strides since the collection of highland rocks by the Apollo 14,15,16, and 1 7 missions. Many types of information have been interpreted and synthesized, including petrologic and geochemical data collected on highlands samples and photographic and geochemical data, covering large portions of the moon's surface, collected by orbiting spacecraft. Research on igneous pro...
Eos, Transactions American Geophysical Union, 1978
The similarity of the airless intense ly cratered surfaces of Mercury and the moon (Figures la an... more The similarity of the airless intense ly cratered surfaces of Mercury and the moon (Figures la and 1?)) is in striking contrast to the different den sities of the two objects. The similar geologic history inferred from the sur face record is surprising, since the different size and density of these two bodies might suggest different amounts of radiogenic heating, sili cate/metal ratios, and thermal conduc tivity (Figure 2
SAE Technical Paper Series, 1993
ABSTRACT Applied research and technology development (R&TD) is often characterized by unc... more ABSTRACT Applied research and technology development (R&TD) is often characterized by uncertainty, risk, and significant delays before tangible returns are obtained. Given the increased awareness of limitations in resources, effective R&TD today needs a method for up-front assessment of competing technologies to help guide technology investment decisions. Such an assessment approach must account for uncertainties in system performance parameters, mission requirements and architectures, and internal and external events influencing a development program. The methodology known as decision analysis has the potential to address these issues. It was evaluated by performing a case study assessment of alternative carbon dioxide removal technologies for NASA"s proposed First Lunar Outpost program. An approach was developed that accounts for the uncertainties in each technology's cost and performance parameters as well as programmatic uncertainties such as mission architecture. Life cycle cost savings relative to a baseline, adjusted for the cost of money, was used as a figure of merit to evaluate each of the alternative carbon dioxide removal technology candidates. The methodology was found to provide a consistent decision-making strategy for the develpoment of new life support technology. The case study results provided insight that was not possible from more traditional analysis approaches.
SAE Technical Paper Series, 1994
Reviews of Geophysics, 1980
A survey of published descriptions of 32 of the largest, least eroded terrestrial impact structur... more A survey of published descriptions of 32 of the largest, least eroded terrestrial impact structures reveals that the amount of melt at craters in crystalline rocks is approximately 2 orders of magnitude greater than at craters in sedimentary rocks. In this paper we present a model for the impact process and examine whether this difference in melt abundance is due to differences in the amount of melt generated in various target materials or due to differences in the fate of the melt during late stages of the impact. The model consists of a theoretical part for the early stages of impact, based on a Birch‐Murnaghan equation of state, a penetration scheme after Shoemaker (1963), and an attenuation model modified from Gault and Heitowit (1963), and a descriptive part for the later stages of impact, based on field observations at the large terrestrial craters. The impacts of iron, stone, permafrost, and ice meteorites 1 km in diameter into crystalline, carbonate, dry sandstone, ice‐satur...
Physics of The Earth and Planetary Interiors, 1977
Papers are presented outlining various comparisons of Mercury and the moon. Specific topics inclu... more Papers are presented outlining various comparisons of Mercury and the moon. Specific topics include the planetary magnetism and the interiors of the moon and Mercury, the relationship between crustal tectonics and internal evolution, global tectonics, the origin and relative age of lunar and Mercurian intercrater plains, and the relative preservation states of secondary craters. Comparisons are also discussed between lunar
SAE Technical Paper Series, 1991
Space suits and life support equipment will come in intimate contact with Martian soil as aerosol... more Space suits and life support equipment will come in intimate contact with Martian soil as aerosols, wind blown particles and material thrown up by men and equipment on the Martian surface. For purposes of this discussion the soil is assumed to consist of a mixture of cominuted feldspar, pyroxene, olivine, quartz, titanomagnetite and other anhydrous and hydrous iron bearing oxides, clay minerals, scapolite and water soluble chlorides and sulfates. The soil may have photoactivated surfaces that acts as a strong oxidizer with behavior similar to hydrogen peroxide. The existing data about the Mars soil suggests that the dust and sand will require designs analogous to those uses on equipment exposed to salty air and blowing sand and dust. The major design challenges are in developing high performance radiators which can be cleaned after each EVA without degradation, designing seals that are readily cleaned and possibly in selecting materials which will not be degraded by any strong oxida...
Lunar soil may be fabricated into useful building materials analogous to those used for masonry, ... more Lunar soil may be fabricated into useful building materials analogous to those used for masonry, concrete and ceramic pipe applications on earth. The process has been analyzed theoretically and demonstrated on a laboratory scale. Ceramic manufacture can be integrated into the design of equipment to extract H 2 for lunar soil for in situ rocket propellant production.
Journal of Geophysical Research: Solid Earth, 1993
The controversy that raged through the 1950s-1970s over similarities and differences between mete... more The controversy that raged through the 1950s-1970s over similarities and differences between meteorite impact and volcanic processes is revisited in this paper. We propose that there are quantitative similarities in erosion caused by high-speed ejecta produced by either impacts or volcanic processes. Field and petrographic data from the Manicouagan impact crater, Canada, are used to demonstrate that during the emplacement of the impact melt. sheet, erosion occurred at a rate of-•2562 kg m-2 s-1. Field data for the Mount St. Helens lateral blast of May 18, 1980, suggest an erosion rate of 2! kg m-2 s-1 , and field data for a small pyroclastic flow on August 7, 1980, suggest an erosion rate of-•14 kg m-• s-1. It is proposed that these three rates were determined dominantly by the momentum of the ejecta, and a quantitative formulation based on lofting theory is given. A new application of the Monte Carlo approach to analysis provides minimum, most likely, and maximum estimates for both the field and the theoretical analyses. The substantial erosion that occurs by fast moving flows results in mixing of stratigraphic components over large distances and to very fine scales. L. Wilson and coworkers ([•l[•, for example, the review by Wilson et al. [1987]). Larg'e:i:ømputer models now provide insight into dynamic processes. For example, Kieffer [1984] used a Rocketdyne nozzle model to improve calculational accuracy for her proposed model for supersonic flow during the lateral blast at Mount St. He!ens [Kieffer, 1981]. Supercomputer models can now be used to examine the influence of a number of geometric and fluid-dynamical parameters on volcanic eruption processes [Wohletz et al., 1984; Valentine
Journal of Geophysical Research: Solid Earth, 1978
The Rb‐Sr isotopic data for mineral separates from a rock of the Manicouagan impact melt sheet de... more The Rb‐Sr isotopic data for mineral separates from a rock of the Manicouagan impact melt sheet define an isochron of age T = 214 ± 5 (2σ) m.y. and an initial Sr87/sr86 ratio I = 0.70991 ± 0.00007 (2σ). This age is in excellent agreement with the K‐Ar age of 210 ± 8 (2σ) m.y. of Wolfe [1971] and represents the time of crystallization of the melt sheet. Four whole rock samples yield age‐corrected I values ranging from 0.70965 to 0.71006. These high I values are consistent with geological and geochemical arguments that the melt sheet was derived by total melting of Grenville basement rocks during the impact event 214 m.y. ago.
Journal of Geophysical Research, 1978
Calculations for the heat transfer between superheated silicate melt and evenly dispersed I-mm co... more Calculations for the heat transfer between superheated silicate melt and evenly dispersed I-mm cold clasts (a model for impact melt rocks) indicate that (1) most of the thermal gradients are smoothed out in 100 s, (2) the extent to which cold debris is melted is slightly more than proportional to the fractional difference of the equilibration temperature between the solidus and the liquidus of the melt, (3) smaller clasts are preferentially dissolved, (4) the melting of clasts depends on the instantaneous local temperature of the melt in the region of the clasts, and hence clasts can melt during cooling whose liquiduses are higher than the equilibration temperature, and (5) the rate of equilibration is sufficiently high that clasts whose dissolution in the melt is slow may be preserved. Calculations for cooling of the 200-m-thick melt sheet at Manicouagan suggest that complete crystallization takes 35 years at 10 m from the edge and 1600 years at the center. Failure to consider the latent heat of fusion results in estimates of these times which are too short by about a factor of 2. The time to cool to a given temperature is proportional to the square of the distance from the boundary of the melt sheet only when the finite nature of the sheet is unimportant. 1. INTRODUCTION Large meteorite impacts into crystalline igneous and metamorphic rocks on the earth and moon characteristically produce clast-laden impact melt rocks. These rocks, whether from the earth or moon, typically have fine-grained holocrystalline to glassy matrices surrounding up to about 25% mineral clasts 0.1-1.0 mm across and a much smaller volume fraction of lithic fragments ranging in size up to tens of meters. The clasts which are observed for the most part lack the vitrification, planar features, and kink bands characteristic of minerals shocked to pressures over 50 kbar. The specific example discussed here is the 200-m-thick sheet from the 65-km-diameter M anicouagan structure in Quebec. Except for some details, such as the exact thickness of sheet used and the temperature ranges for melting, the calculations are generally applicable to any of the larger terrestrial or lunar craters. The objective of this paper is to model numerically the heat flow both on the scale of the clasts and melt and on the larger scale of loss of heat from the melt sheet as a whole. Such modeling places limits on (1) the time before the viscosity of the melt increases dramatically because the clast-melt thermal interactions trigger nucleation, (2) the temperature of the clasts and melt prior to mixing, and (3) the time scale for crystallization of the melt sheet as a whole. Before the calculations of heat transfer are discussed, it must be emphasized that the processes modeled here take place relatively late in the cratering process, essentially after the excavation has been completed. The cratering process can be divided into a series of steps, as is discussed in a paper in this issue by Simonds et al. [1978] and the papers referenced therein. These steps are as follows: 1. Meteorite collision and passage of compressive shock wave is the first step. To yield the 10 aø ergs estimated for the M anicouagan event, an impact stony meteorite with a typical velocity of' 17 km/s would have to be about 8 km across and take about • s to complete its impact. A compressional shock wave would expand radially outward from the point of impact. The peak shock pressure near the point of impact will be over Copyright ¸ 1978 by the American Geophysical Union.
Journal of Geophysical Research: Solid Earth, 1978
The 65-km-diameter Manicouagan impact structure has an eroded 230-m-thick sheet of clast-laden, i... more The 65-km-diameter Manicouagan impact structure has an eroded 230-m-thick sheet of clast-laden, impact melt rock with an estimated preerosional volume of > 270 km 3. All samples are characterized by mineral and lithic clasts or their incompletely digested remnants. Drawing upon previous theoretical studies of shock waves, we suggest that the Mani6ouagan melt formed in 1 or 2 s in a 5-km-radius hemisphere near the point of impact. The melt accelerated to a few kilometers per second, and the melt and the less shocked debris surrounding it flowed downward and outward for a few minutes until the melt formed a lining of a 5-to 8-km-deep, 15-to 22-km-radius cavity. Extremely turbulent flow thoroughly homogenized the melt and promoted the incorporation and progressive digestion of slower moving, less shocked, cooler debris surrounding the melt. This debris had been finely fragmented, but not melted, to grain sizes of less than 1 mm by the passage of the shock waves. Because of the fine grain size, the melt and fragmented debris equilibrated thermally in about 100 s. During thermal equilibration, virtually all clastic debris (i.e. alkali feldspar, biotite, hornblende, garnet, and scapolite), other than highly refractory quartz and plagioclase as well as many of the centimeter size lithic clasts other than anorthosite, were digested. The preservation of quartz and plagioclase mineral clasts implies that the clasts and melt equilibrated to temperatures near but not above the liquidus. Plagioclase nucleation was initiated by the drop in temperature and possibly by direct nucleation on undigested debris. The initiation of crystallization vastly increased the melt viscosity, preventing settling of 10-mm clasts of basement. Flow of melt through basement fractures is evidence that readjustment of the crater floor took place during the period of clast-melt thermal equilibration.