Shock Recovery Experiments Research Articles

Effect of shock compression on single crystalline silicon

A series of shock-recovery experiments were performed on single crystals of silicon and germanium using a propellant gun and the laser-driven miniflyer method. Characterizations of the recovered samples by X-ray diffraction (XRD) analysis and Raman spectroscopy revealed the absence of additional constituents such as metastable phases and high-pressure phases. The XRD patterns for shocked samples are consistent with a powder XRD pattern corresponding to the cubic-diamond phase. The formation of copper silicide (Cu3Si) was confirmed in the sample shocked at 38 GPa. The formation of an additional band and the deviation of a center frequency peak from the cubic-diamond phase of silicon and germanium were evident in the Raman spectroscopy results. The results of XRD and Raman spectroscopy indicated that crystalline size reduction, rather than the formation of metastable phases, occurred.

Plagioclase breakdown as an indicator for shock conditions of meteorites

The collision history of asteroids in the early Solar System is difficult to reconstruct. A study of plagioclase breakdown using X-ray diffraction measurements under increasing pressures and temperatures suggests that peak pressures in collisions that formed shocked meteorites have been overestimated. Shocked meteorites that were formed when their parent body underwent shock metamorphism often contain the mineral plagioclase either in an amorphous form or in its high-pressure phase. The peak pressures in shock metamorphism can be constrained by shock-recovery experiments that determine the amorphization pressures of plagioclase1,2,3. However, in these experiments temperatures have been unrealistically low and timescales much shorter than those in natural events. Here we present in situ X-ray diffraction measurements of two kinds of plagioclase feldspar in conditions of increasing pressures and temperatures. We find that the amorphization pressure of plagioclase decreases with increasing temperature, suggesting that previous studies overestimated this parameter1,2,3. We also found that the mineral jadeite forms first from amorphous plagioclase, whereas the nucleation of other minerals such as stishovite or garnet is significantly delayed. The occurrence of jadeite in shocked meteorites that do not contain stishovite4,5,6,7,8 can therefore be explained as a result of the crystallization kinetics. We conclude that the study of plagioclase breakdown can constrain the pressure–temperature–time history of shock events, and thus help to reconstruct the collisional history of asteroids in the early Solar System.

Orientation dependence of shock-induced twinning and substructures in a copper bicrystal

Shock recovery experiments have been conducted to assess the role of shock stress and orientation dependence on substructure evolution and deformation twinning of a [1 0 0]/ [ 0 1 1 ¯ ] copper bicrystal. Transmission electron microscopy of the post-shock specimens revealed that well-defined dislocation cell structures developed in both grains and the average cell size decreased with increasing shock pressure from 5 to 10 GPa. Twinning occurred in the [1 0 0] grain, but not the [ 0 1 1 ¯ ] grain, at the 10 GPa shock pressure. The stress and orientation dependence of incipient twinning can be predicted by the stress and orientation conditions required to dissociate slip dislocations into glissile twinning dislocations. The dynamic widths between the two partials are calculated considering the three-dimensional deviatoric stress state induced by the shock as calculated using plane-strain plate impact simulations and the relativistic and drag effects on dislocations moving at high speeds.

Shock-induced disproportionation of mullite (3Al2O3⋅2SiO2)

Shock-recovery experiments have been performed on high-purity mullite polycrystals in the pressure range up to 72GPa. The recovered samples have been examined by an x-ray diffraction method, nuclear magnetic resonance spectroscopy, and transmission electron microscopy. The samples shocked above 65GPa contain an amorphous SiO2 phase and a γ-Al2O3 phase, indicating that a rapid disproportionation reaction of mullite is induced by shock compression. The recovered amorphous SiO2 has a mean Si–O–Si bond angle roughly 7° narrower than that of the fused SiO2 glass, indicating the formation of the densified amorphous SiO2 phase. The γ-Al2O3 phase is crystallized as very fine particles with grain sizes less than 10nm in the matrix of the desified amorphous SiO2 phase. The crystallization of γ-Al2O3 is expected to occur during a pressure-release process owing to the crystal size effect concerning the phase stability of Al2O3.

Simulation experiments for shocked primitive materials in the Solar System

Shock recovery experiments were conducted on porous mixtures (initial porosity 35 ± 5%) in silicate–metal and silicate–metal–sulfide systems in an attempt to simulate impact phenomena of unconsolidated porous materials similar to ordinary chondrites in a wide range of shock pressures from 20 to 70 GPa. The textures and chemical compositions of shocked samples were investigated in detail. Features such as grain deformation, fracture density decrease, and heterogeneous meltings are found. At < 30 GPa, mechanical effects of the shock process, such as silicate fracturing and metal elongation, are dominant. Morphological analysis of metal grains in shocked samples reveals good correlation between the degree of deformation and the shock pressure. The metal grain aspect ratio may be a good indicator of shock pressure. At higher pressures, thermal effects, which are enhanced in the shock compression of porous media, become prominent. Above 30 GPa, silicate grain fractures disappear, and silicate darkening dominates. Shock-induced melting in the shock veins and melt networks is observed and interpreted as localized in situ melting features, the heat source of which is frictional heating between grains. Thin veins and melt pockets of sulfide–metal melt are the principal characteristics in this type of sample. Melting features of metal–sulfide systems alter the spectral property of meteoritic bodies. The initial porosity of a target may have been an important factor in impact processes in the early Solar System.

Dynamic deformation and fracture of mullite (3Al2O3·2SiO2) ceramics under hypervelocity impact

Abstract Shock-recovery experiments have been performed on mullite ceramics to clarify the effect of a phase transition on the microstructural change and deformation mechanism under shock loading. The recovered samples have been examined using the X-ray diffraction method and transmission electron microscope observation. In the samples shocked above the phase-transition pressure, an amorphization of mullite occurs. Mullite nano-crystals with grain sizes less than 10 nm are dispersed in the amorphous phase, indicating that the relatively large starting mullite crystals become nano-crystals accompanied with the amorphization. Mullite bumper-shield experiments have also been performed to examine the influence of shock-induced microstructural changes to ultimate fracture under hypervelocity impact. The results suggest that the phase transition of mullite has an effect on protection against high-velocity impact.

Microbial Rock Inhabitants Survive Hypervelocity Impacts on Mars-Like Host Planets: First Phase of Lithopanspermia Experimentally Tested

The scenario of lithopanspermia describes the viable transport of microorganisms via meteorites. To test the first step of lithopanspermia, i.e., the impact ejection from a planet, systematic shock recovery experiments within a pressure range observed in martian meteorites (5-50 GPa) were performed with dry layers of microorganisms (spores of Bacillus subtilis, cells of the endolithic cyanobacterium Chroococcidiopsis, and thalli and ascocarps of the lichen Xanthoria elegans) sandwiched between gabbro discs (martian analogue rock). Actual shock pressures were determined by refractive index measurements and Raman spectroscopy, and shock temperature profiles were calculated. Pressure-effect curves were constructed for survival of B. subtilis spores and Chroococcidiopsis cells from the number of colony-forming units, and for vitality of the photobiont and mycobiont of Xanthoria elegans from confocal laser scanning microscopy after live/dead staining (FUN-I). A vital launch window for the transport of rock-colonizing microorganisms from a Mars-like planet was inferred, which encompasses shock pressures in the range of 5 to about 40 GPa for the bacterial endospores and the lichens, and a more limited shock pressure range for the cyanobacterium (from 5-10 GPa). The results support concepts of viable impact ejections from Mars-like planets and the possibility of reseeding early Earth after asteroid cataclysms.

Effect of phase transition in shock-recovered silicon

A series of shock-recovery experiments on a single crystal of silicon up to 38 GPa and characterizations of the recovered samples by x-ray diffraction analysis, Raman spectroscopy, and microscopic observations were performed for a better understanding of residual effects after shock loading by using a propellant gun. The x-ray diffraction trace of each sample revealed the absence of additional constituents including metastable phases and high-pressure phases of silicon except for 11 and 38 GPa. At 11 GPa, small amounts of metastable phases of silicon were obtained. The formation of copper silicide (Cu3Si) was confirmed in the sample shocked at 38 GPa. Considering the surface morphology revealed by microscopic observation, a thermochemical reaction through the melting of silicon resulted in the formation of Cu3Si. An additional band and the center frequency deviation of a peak were shown in the Raman spectroscopy results. The results of x-ray diffraction and Raman spectroscopy indicated that crystalline size reduction rather than the formation of metastable phases occurred. Structural deformation rather than the thermal effect caused by a shock-induced temperature rise may be responsible for the disappearance of metastable phases, which were observed in other high-pressure experiments.

Assessment of shock effects on amphibole water contents and hydrogen isotope compositions: 2. Kaersutitic amphibole experiments

To constrain the influence of impact shock on water and hydrogen isotope signatures of Martian meteorite kaersutites, we conducted shock recovery experiments on three terrestrial kaersutite crystals. Homogeneous impact shock to 32 GPa, commensurate with shock levels experienced by Martian meteorite kaersutites, led to increases in kaersutite water contents (ΔH 2O = 0.25–0.89 wt.%), decreases in Fe 3+/ΣFe (4–20%), and enrichments in hydrogen isotope composition (ΔD = + 66 to + 87‰) relative to pre-shock values. The latter values represent the largest shock-induced hydrogen isotope fractionations measured to date. These observations are explained most completely by a two-step shock process. First, shock-induced devolatilization led to hydrogen isotope enrichment through preferential loss of H relative to D. Second, reaction of the kaersutite with the ambient atmosphere led to increased water contents and reduced Fe. Fe reduction and water addition via the reaction Fe 2+ + OH − ↔ Fe 3+ + O 2− + ½H 2 explain the Fe 3+/ΣFe data and some of the water data. Further water addition mechanisms (irreversible adsorption, shock implantation) are necessary to fully explain the increased water contents. Addition of water from the terrestrial atmosphere, which is isotopically light relative to the experimental kaersutite compositions, means the measured hydrogen isotope enrichments are likely minima. The measured (minimum) levels of hydrogen isotope enrichment are relevant to the hydrogen isotope variability within and among Martian kaersutites, but are minor relative to their absolute δD values. Alternatively, addition of water from the enriched Martian atmosphere could explain both Martian kaersutite hydrogen isotope variability and absolute δD values. However, the low Martian kaersutite water contents leave little room for significant water addition. The importance of the ambient atmosphere to the outcome of the shock experiments makes it difficult to translate our results to Mars given the unknown influence of its more tenuous atmosphere on the processes observed in the experiments. Our results suggest that shock is a feasible mechanism for influencing Martian kaersutite water contents and hydrogen isotope compositions but that its complex signature precludes precise determination of that influence.

Shock Wave Chemical Reactions; Synthesis of Carbon Nitrides

A series of shock recovery experiments up to ~50 GPa were performed on reactions to form carbon nitrides. Nitrogen-rich starting materials, included a C-N-O amorphous precursor, dicyandiamide, melamine, and a mixture of carbon tetrahalide and sodium dicyanoamide, were used and the recovered samples were investigated by X-ray diffraction technique, elemental analysis, transmission electron microscopy and so on. Experimental results showed formation of a new carbon nitride, high stability of melamine up to a shock pressure of 37 GPa, and production of amorphous C-N materials with a highest N/C ration of 1.26 from the reaction between carbon tetrahalide and sodium dicyanoamide. We extended to the system C3N4-Si3N4 based on the recent results on synthesis of spinel-type nitrides. Shock wave chemical reactions provide a route for synthesizing novel materials including not only high-pressure phases but also metastable, unique substances.

Impact-shock behavior of Mg- and Ca-sulfates and their hydrates

Shock recovery experiments on MgSO 4, CaSO 4, and their hydrates (kieserite, epsomite, and bassanite) were performed to investigate shock-induced dehydration and decomposition at shock pressures up to 36 GPa. The recovered solid samples indicated dehydration at pressures below 24 GPa, but no clear evidence was found for possible decomposition of MgSO 4 and CaSO 4 to produce MgO or CaO as final products. These sulfates and hydrates have been observed on the surface of Mars, and the present experimental results can be applied towards understanding the presence of surface water on Mars and the recycling of water by impacts. This finding that the sulfate hydrates undergo dehydration upon impact, as well as the fact that the sulfates CaSO 4 and MgSO 4 absorb moisture, suggests the total amount of water on Mars has remained almost unchanged since the time of formation of the planet.

Experimental shock decomposition of siderite and the origin of magnetite in Martian meteorite ALH 84001

Abstract Shock recovery experiments to determine whether magnetite could be produced by the decomposition of iron‐carbonate were initiated. Naturally occurring siderite was first characterized by a variety of techniques to be sure that the starting material did not contain detectable magnetite. Samples were shocked in tungsten‐alloy holders (W = 90%, Ni = 6%, Cu = 4%) to further ensure that any iron phases in the shock products were contributed by the siderite rather than the sample holder. Each sample was shocked to a specific pressure between 30 to 49 GPa. Transformation of siderite to magnetite as characterized by TEM was found in the 49 GPa shock experiment. Compositions of most magnetites are &gt;50% Fe+2 in the octahedral site of the inverse spinel structure. Magnetites produced in shock experiments display the same range of sizes (˜50–100 nm), compositions (100% magnetite to 80% magnetite‐20% magnesioferrite), and morphologies (equant, elongated, euhedral to subhedral) as magnetites synthesized by Golden et al. (2001) and as the magnetites in Martian meteorite Allan Hills (ALH) 84001. Fritz et al. (2005) previously concluded that ALH 84001 experienced ˜32 GPa pressure and a resultant thermal pulse of ˜100–110°C. However, ALH 84001 contains evidence of local temperature excursions high enough to melt feldspar, pyroxene, and a silica‐rich phase. This 49 GPa experiment demonstrates that magnetite can be produced by the shock decomposition of siderite as a result of local heating to &gt; 470°C. Therefore, magnetite in the rims of carbonates in Martian meteorite ALH 84001 could be a product of shock devolatilization of siderite as well.

The ICDP Lake Bosumtwi impact crater scientific drilling project (Ghana): Core LB‐08A litho‐log, related ejecta, and shock recovery experiments

Abstract— The 1.07 Myr old Lake Bosumtwi impact crater in Ghana was drilled within the framework of the International Continental Scientific Drilling Project (ICDP). Hole LB‐08A, drilled into the outer flank of the central uplift and with a total depth of 451 m, yielded 215.71 m of impact‐related rocks. This paper summarizes observations of the lithological logging on core LB‐08A. Between a depth of 235.6 and ∼260 m, the section consists of a melt‐bearing allochthonous, polymict, and mostly clast‐supported impact breccia. Down to ∼418 m, the section comprises a rather uniform unit of meta‐graywacke alternating with phyllite to slate (lower greenschist facies); few (par‐) autochthonous impact breccia bodies and rare impact dike breccias are present. The lowermost part of the section contains several centimeter‐ to decimeter‐thick melt‐bearing breccia dikes in country rocks identical to those occurring above. Omnipresent fracturing was mapped in a qualitative manner. Most prominent shock effects in the uplifted target rocks comprise planar fractures and deformation elements in quartz and polysynthetic twinning in carbonate minerals; the maximum shock pressure as evidenced by quartz is below 26 GPa. The allochthonous breccias occasionally contain a few vol% of melt particles. Suevites occur outside the crater rim, carrying diaplectic crystals, coesite, and ballen quartz as well as true melt glasses and a variety of lithic clasts, among those spectacular staurolite‐rich mica‐schists. The recorded shock level in the uplifted target rocks is lower than expected and modeled. Shock recovery experiments with analogue carbonaceous graywackes at 34 and 39.5 GPa yielded nearly complete transformation of quartz into diaplectic glass. We therefore exclude a specific shock behavior of the soft, fluid‐rich target material (carbonaceous graywackes, shales, slates) in core LB‐08A as the prime or only reason for the melt deficit and the generally low shock levels recorded inside the Lake Bosumtwi impact crater.

Formation of ultrafine particles from impact-generated supercritical water

Shock-recovery experiments were performed targeting an olivine, iron, and water mixture to simulate a low-velocity ocean impact event. The maximum pressure in the sample container reached 20 GPa during the experiments. Ultrafine particles (UPs) of olivine and metal oxides were newly formed, even at pressures less than their vaporization pressure (150–200 GPa). Impedance-match and thermodynamic calculations suggest that supercritical water formed during the shock wave traversal. Such supercritical water dissolves impacted materials and precipitates UPs. Results of our experiments further suggest that many extraterrestrial objects that have impacted on oceans might have been converted to large masses of UPs and probably influenced the climate and UV shielding, especially during the late Hadean and early Archean eras.

Effect of shock on the magnetic properties of pyrrhotite, the Martian crust, and meteorites

We performed planar shock recovery experiments on natural pyrrhotite at pressures up to 6.9 GPa. We find that high‐field isothermal remanent magnetization in pyrrhotite is demagnetized up to 90% by shock due to preferential removal of low coercivity components of magnetization. Contrary to static experiments, we do not observe complete demagnetization. Post shock permanent changes in magnetic properties include increasing saturation isothermal remanent magnetization, bulk coercivity and low‐temperature memory, and changes in squareness of hysteresis. These changes are consistent with an increase in the volume fraction of single domain grains. The lack of magnetic anomalies over large Martian impact basins is not expected to be solely due to shock demagnetization of the crust. We find that pyrrhotite‐bearing rocks and meteorites can retain records of Martian magnetic fields even if shocked to pressures approaching 7 GPa. However, some paleointensity techniques may underestimate this field.

Shock Wave Synthesis and Exploration of High-pressure Nitrides and Related Materials

AbstractWe have successfully developed a method to manufacture spinel-type Si3N4 and also a chemical treatment method to separate the spinel-type phase from the low-pressure phases. Similar methods could be applied for the SiAlON systems. In order to explore high-pressure nitrides and oxynitrides, we extended toward the system Si3N4-AlN-Al2O3- SiO2. According to the results of in situ measurements of the high-pressure behavior up to pressures of 200 GPa, there appears to be post-spinel phase in the system. This is consistent with the results from the first principles calculations. However we could not obtain the post-spinel phase by the shock recovery experiments at present. We also carried out shock recovery experiments on carbon nitrides and related materials. Experimental results showed formation of a new carbon nitride, high stability of melamine up to a shock pressure of 37 GPa, and production of amorphous C-N materials with a highest N/C ration of 1.26 from the reaction between carbon tetrahalide and sodium dicyanoamide. We tried further to extend toward the systems C3N4-Si3N4 and Mg2SiO4-Si3N4, after taking into account the results on shock synthesis of spinel-type nitrides.

Bugbuster—survivability of living bacteria upon shock compression

Shock recovery experiments were conducted on suspensions of 10 6/ml E. coli bacteria contained in a water-based medium that is emplaced within stainless steel containers. The water is shocked and recovered. These experiments simulate the environment of bacteria residing either in surface bodies of water or in subsurface water-filled cracks in rocks. Early Earth life is likely to have existed in such environments. However, the E. coli are not believed to be representative of early life and are merely used here for initial experiments. Some 10 − 2 to 10 − 4 of the bacteria population survived initial (800 ns duration) shock pressures in water of 220 and 260 MPa. TEM images of shock recovered bacteria indicate cell wall rupture and delamination. This appears to be the mortality mechanism. The TEM images indicate cell wall indentations may be occurring as would be consistent with Rayleigh–Taylor or Richtmyer–Meshkov fluid instabilities. In the present case, we consider the experiments as representing three layers of fluids: (1) The water-based medium, a stronger and possibly denser cell wall medium, and the interior of the cell cytoplasm. Variations of only 10–15% are expected in density. (2) A second mechanism that may cause cell wall failure is the multiple shock (nearly isentropic) compression freezing of liquid water medium into ice VI or ice VII high pressure phase that are 20% to 25% denser than the liquid. The decrease in volume associated with the transformation is expected to induce overpressures in the still liquid cell cytoplasm. Cell dynamic tensile wall strength thus appears to be a critical parameter from either of the above failure modes. Because the strain rate dependence of cell wall tensile strength is unstudied, we utilize the Grady and Lipkin [D.E. Grady, L. Lipkin, Criteria for impulsive rock fracture, Geophys. Res. Lett. 7 (1980) 255–258] model of tensile failure versus time scale (strain rate). Our single datum is fit to this law and we assume that at low strain rates, overpressures exceeding the cell Turgor pressure require on the order of ∼10 3 s. This model which has been applied to brittle media and metals for describing failure may permit application of short duration laboratory experiments as in the present ones to infer responses of organisms to much lower shock pressures, but for longer time scales (10 0 to 10 3 s) of planetary impacts. Using the present data for E. coli and applying the Grady and Lipkin model, we find that a 1.5 km diameter impactor will cause mortality of bacteria within a radius of 10 2 km but upon stress related attenuation the subsurface bacteria outside of this radius should survive.

Sinoite (Si2N2O) shocked at pressures of 28 to 64 GPa

Shock recovery experiments of sinoite (Si 2 N 2 O) were carried out in a pressure range of 28-64 Gpa. Post-shock samples were investigated by optical microscopy, X-ray diffraction, micro Raman spectroscopy, and transmission electron microscopy coupled with energy dispersive X-ray analysis. Sinoite was stable up to ~28 Gpa, being partially amorphous at 34 Gpa, and almost completely amorphized above 41 Gpa. These results are consistent with the observation that sinoite is found in enstatite chondrites classified into shock stage S2, and imply that sinoite may not be a crystallization product from impact melts and that it may be a metamorphic product of high temperatures and relatively low pressure.

A new carbon nitride synthesized by shock compression of organic precursors

A series of shock recovery experiments up to ∼50 GPa were carried out on three nitrogen-rich materials of a C–N–O amorphous precursor, dicyandiamide and melamine. The powder X-ray diffractions (XRD) of recovered samples show that carbon nitride phases are formed. They are β-C 3N 4 and a new crystalline phase. The new phase is indexed as a monoclinic cell with a=0.981 nm, b=0.723 nm, c=0.561 nm, β=95.2° and V cell=0.3966 nm 3. Melamine was very stable and did not decompose up to ∼37 GPa. This new phase is considered to form during the adiabatic release process with an extremely high quenching rate (∼10 9 K/s) and shock compression may provide a novel synthesis route for various C–N phases from appropriate organic materials.

Flyer Acceleration by Pulsed Laser and its Application to Shock-Recovery Experiment on MnF2

An experimental method using a laser-driven flyer has been developed for a shock-recovery experiment. A laser-driven flyer has been accelerated to a high speed using a plasma-confinement target assembly with a relatively modest laser intensity (<5 GW/cm2) and its acceleration history has been monitored. A shock recovery experiment of rutile-type MnF2 is performed using the laser-driven flyer with a velocity of 1.1 km/s and a metastable phase (α-PbO2-type MnF2) is recovered with a yield of 83.2%.