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Feather features (FFs) in quartz consist of a planar fracture (PF) and associated fine lamellae (FF lamellae; FFL) and have been observed in various natural impact structures. However, the mechanisms and conditions of FF formation are poorly understood. We conducted shock recovery experiments on granite using decaying compressive pulses to investigate the formation conditions of FFs. We characterized the recovered samples using an optical microscope equipped with a universal stage, a scanning electron microscope combined with an electron back‐scattered diffraction detector, and a transmission electron microscope. We found that FFs are formed over a wide range of peak pressures (2–18 GPa) and that FFs can be divided into at least three types (I–III) based on the crystallographic orientation of the PFs and FFL, the angle between the orientation of the FFL and the propagation direction of the compression wave, and the presence/absence of amorphous silica in the FFL. The peak pressures that produce type I–III FFs are estimated to be <12, 12–14, and >16 GPa, respectively. We propose that FFs can be used as a shock barometer for quartz‐bearing rocks. Plain Language Summary: Our research focused on a unique deformation feature in quartz, known as feather features (FFs), which are found where hypervelocity impacts of celestial bodies have occurred. These features include a main crack and several fine, feather‐like lines emanating from the main crack. We conducted shockwave experiments on granite, a common quartz‐bearing rock by simulating the shock conditions of impacts onto Earth's surface. We used various microscopic techniques to observe the experimentally shocked quartz. We show that FFs form under a wide range of pressures from 20,000× to 180,000× atmospheric pressure. The FFs can be divided into three types relating to the peak pressure, based on the orientation of the feather‐like lines with respect to the crystal lattice and the direction of shockwave propagation, and whether vitrification occurred. At pressures below ∼120,000× atmospheric pressure, the main crack and fine lines have specific orientations (type I), but these orientations change when the pressure is >120,000× atmospheric pressures (type II). The feather‐like lines transform from simple cracks to structures filled with glass at a peak pressure of >140,000–160,000× atmospheric pressure (type III). The nature of the FFs means that the three types of FFs are a useful shock barometer for ancient impact events. Key Points: Impact experiments revealed that feather features in quartz are produced at peak pressures of 2–18 GPaThe feather features can be divided into at least three types that relate to the peak pressureFeather features can be used as a shock barometer for estimating peak pressures in geological studies [ABSTRACT FROM AUTHOR]

Knowledge of the shock behavior of planetary materials is essential to interpret shock metamorphism documented in rocks at hypervelocity impact structures on Earth, in meteorites, and in samples retrieved in space missions. Although our understanding of shock metamorphism has improved considerably within the last decades, the effects of friction and plastic deformation on shock metamorphism of complex, polycrystalline, non‐porous rocks are poorly constrained. Here, we report on shock‐recovery experiments in which natural granite was dynamically compressed to 0.5–18 GPa by singular, hemispherically decaying shock fronts. We then combine petrographic observations of shocked samples that retained their pre‐impact stratigraphy with distributions of peak pressures, temperatures, and volumetric strain rates obtained from numerical modeling to systematically investigate progressive shock metamorphism of granite. We find that the progressive shock metamorphism of granite observed here is mainly consistent with current classification schemes. However, we also find that intense shear deformation during shock compression and release causes the formation of highly localized melt veins at peak pressures as low as 6 GPa, which is an order of magnitude lower than currently thought. We also find that melt veins formed in quartz grains compressed to >10–12 GPa contain the high‐pressure silica polymorph stishovite. Our results illustrate the significance of shear and plastic deformation during hypervelocity impact and bear on our understanding of how melt veins containing high‐pressure polymorphs form in moderately shocked terrestrial impactites or meteorites. Plain Language Summary: When asteroids, comets, or smaller fragments thereof impact the solid surfaces of planets, moons, or other asteroids, the rocks they strike undergo sudden and irreversible changes while an impact crater forms. These material changes are called shock metamorphism and result from the extremely high pressures, temperatures, and deformation rates caused by the impact. However, the role of rapid shear deformation on impact heating and shock metamorphism is poorly understood. Using a novel experimental setup, we performed shock‐wave experiments with granite, a naturally occurring rock, that allows us to study the role of extreme deformation rates during impact‐crater formation. Furthermore, our experimental setup allows us to avoid several pitfalls such as excavation and ejection of shocked material from a growing impact crater or multiple reflections of shock waves at sample containers that typically plagued previous experiments. We find that intense shear deformation during crater formation results in significant but highly localized heating. This additional heating causes melting of granite at shock pressures as low as 6 GPa, which is about 10 times less than currently thought. Our findings may explain how thin melt veins often observed in shock‐metamorphosed meteorites or rocks sampled from terrestrial impact craters have formed. Key Points: We performed shock recovery experiments with granite and spherically decaying compressive waves; numerical models constrain peak pressuresShocked granite samples are found to retain pre‐impact stratigraphy and to document shock‐stage transitions between <0.5 and ∼18 GPaShear‐induced melting of granite at bulk peak pressures as low as 6 GPa; stishovite nucleated as a liquidus phase in melt veins at >10 GPa [ABSTRACT FROM AUTHOR]

Basaltic rocks occur widely on the terrestrial planets and differentiated asteroids, including the asteroid 4 Vesta. We conducted a shock recovery experiment with decaying compressive pulses on a terrestrial basalt at the Chiba Institute of Technology, Japan. The sample recorded a range of pressures, and shock physics modeling was conducted to add a pressure scale to the observed shock features. The shocked sample was examined by optical and electron microscopy, electron back‐scattered diffractometry, and Raman spectroscopy. We found that localized melting occurs at a lower pressure (∼10 GPa) than previously thought (>20 GPa). The shocked basalt near the epicenter represents "shock degree C" of a recently proposed classification scheme for basaltic eucrites and, as such, our results provide a pressure scale for the classification scheme. Finally, we estimated the total fraction of the basaltic eucrites classified as shock degree C to be ∼15% by assuming the impact velocity distribution onto Vesta. Plain Language Summary: Basaltic rocks occur on numerous planetary bodies, including Mars, the Moon, and the asteroid Vesta. Shock metamorphic features in meteorites from such bodies are the ancient imprints of past impact events. We can extract information about the bombardment histories experienced by such bodies if we have an accurate method to link the degree of metamorphism to the impact conditions. Although two such methods for basaltic rocks have been published, one of these does not have a scale that relates the shock features and peak pressures. In this study, we designed an impact experiment with a terrestrial basalt sample to add a pressure scale to one of these methods. We found that basaltic materials are more easily melted than previously expected. The shock features of our shocked sample match "shock degree C." The required pressure for producing the materials classified into this shock degree is 1–2 × 105 times greater than atmospheric pressure. Our results may provide insights into impact processes on Vesta. We estimate that the total fraction of meteorites from Vesta classified into shock degree C is ∼15%. Key Points: We investigated the shock effects in basaltic rocks with impact experiments and shock physics modelingWe added a pressure scale to the shock degree classification for basaltic eucrites, allowing us to link our results with the Stöffler tableLocalized melting occurs from 10 GPa rather than 20 GPa as previously thought [ABSTRACT FROM AUTHOR]

Shock metamorphism of minerals in meteorites provides insights into the ancient Solar System. Calcite is an abundant aqueous alteration mineral in carbonaceous chondrites. Return samples from the asteroids Ryugu and Bennu are expected to contain calcite‐group minerals. Although shock metamorphism in silicates has been well studied, such data for aqueous alteration minerals are limited. Here, we investigated the shock effects in calcite with marble using impact experiments at the Planetary Exploration Research Center of Chiba Institute of Technology. We produced decaying compressive pulses with a smaller projectile than the target. A metal container facilitates recovery of a sample that retains its pre‐impact stratigraphy. We estimated the peak pressure distributions in the samples with the iSALE shock physics code. The capability of this method to produce shocked grains that have experienced different degrees of metamorphism from a single experiment is an advantage over conventional uniaxial shock recovery experiments. The shocked samples were investigated by polarizing microscopy and X‐ray diffraction analysis. We found that more than half of calcite grains exhibit undulatory extinction when peak pressure exceeds 3 GPa. This shock pressure is one order of magnitude higher than the Hugoniot elastic limit (HEL) of marble, but it is close to the HEL of a calcite crystal, suggesting that the undulatory extinction records dislocation‐induced plastic deformation in the crystal. Finally, we propose a strategy to re‐construct the maximum depth of calcite grains in a meteorite parent body, if shocked calcite grains are identified in chondrites and/or return samples from Ryugu and Bennu. Plain Language Summary: Carbonaceous chondrites are a group of meteorites found on Earth, which contain significant amounts of water and organic materials. Ancient impacts onto their parent bodies caused irreversible changes to the minerals in these meteorites, which is termed shock metamorphism. If the relationship between the metamorphism and intensity of the impact can be understood, it would be possible to elucidate the histories of meteorite parent bodies. We investigated shock metamorphism of calcite, which is an abundant aqueous alteration mineral in carbonaceous chondrites, and may also be present in return samples from the asteroids Ryugu and Bennu. Our experiments involved rapid compression during laboratory impacts onto marble blocks. We found that shocked calcite exhibits a specific feature called undulatory extinction under microscope and quantified the strength of the compressive pulse required to produce this feature, which is 30,000 times greater than the atmospheric pressure. Given that such conditions cannot be easily reached on meteorite parent bodies and/or on Ryugu and Bennu, except during hypervelocity impacts, calcite grains showing this feature provide evidence for past impact events. Key Points: We present a method to efficiently investigate the shock effects in minerals in rock samples with sizes of >20 mmImpact experiments with decaying compressive pulses revealed the shock effects in marble, which is a macro block of calcite (CaCO3)Calcite that experiences compression of >3 GPa exhibits undulatory extinction [ABSTRACT FROM AUTHOR]

Radiation phenomena are usually observed during fracture of quartz-bearing rocks. Since quartz is a piezoelectric material, the associated electrical processes such as the electrification of fracture surface and the flight of electrons between fracture surfaces should be important for radiation during fractures. In this article, supposing that travelling electrons between crack surfaces cause the radiation, we experimentally investigate X-ray emission in a vacuum and visible-light emission in the atmosphere during rock and mineral fracture and verify the consistency of both emissions. The number of electrons in flight between surfaces during fracture that result in X-ray is estimated and the comparison with the number of photons in visible light suggests that one electron repeatedly collides with N2 molecules. The estimated number of collisions resulting in a visible-light emission is slightly less than the expected upper limit. This is reasonable because the collision would cause the light emission not always in the wavelengths of visible light. Moreover, the number of electrons resulting in X-rays is comparable with the number of electrons resulting in the emission of radio waves during fracture obtained in previous studies. Thus, we conclude that the radiations during fracture can be attributed to the flight of electrons between fracture surfaces. Finally, we evaluate the feasibility of observing the X-ray emission in planetary exploration and the radio waves and the visible light in natural earthquakes and find that these radiations are observable. [ABSTRACT FROM AUTHOR]

The Iron Age was the time when people acquired iron processing technology and is generally thought to have begun after 1200 B.C. Some prehistoric iron artifacts made of iron meteorites are dated from the Bronze Age. A nicely preserved meteoritic iron dagger was found in the tomb of King Tutankhamen (1361–1352 B.C.) of ancient Egypt. Yet, its manufacturing method and origin remain unclear. Here, we report nondestructive two‐dimensional chemical analyses of the Tutankhamen iron dagger, conducted at the Egyptian Museum of Cairo. Elemental mapping of Ni on the dagger blade surface shows discontinuous banded arrangements in places with "cubic" symmetry and a bandwidth of about 1 mm, suggesting a Widmanstätten pattern. The intermediate Ni content (11.8 ± 0.5 wt%) with the presence of the Widmanstätten pattern implies the source meteorite of the dagger blade to be octahedrite. The randomly distributed sulfur‐rich black spots are likely remnants of troilite (FeS) inclusions in iron meteorite. The preserved Widmanstätten pattern and remnant troilite inclusion show that the iron dagger was manufactured by low‐temperature (<950 °C) forging. The gold hilt with a few percent of calcium lacking sulfur suggests the use of lime plaster instead of gypsum plaster as an adhesive material for decorations on the hilt. Since the use of lime plaster in Egypt started during the Ptolemaic period (305–30 B.C.), the Ca‐bearing gold hilt hints at its foreign origin, possibly from Mitanni, Anatolia, as suggested by one of the Amarna letters saying that an iron dagger with gold hilt was gifted from the king of Mitanni to Amenhotep III, the grandfather of Tutankhamen. [ABSTRACT FROM AUTHOR]

Asteroid (99942) Apophis is a potentially hazardous asteroid. The Korea Astronomy and Space Science Institute (KASI) recently proposed a rendezvous mission with Apophis, with a planned asteroid observation campaign to help determine the mission strategy in advance. In this study, we performed multicolor photometric observations of Apophis using the 1.0 m telescope at Kawabe Cosmic Park on 2021 March 10. The visible colors (g ′, r ′, and i ′) of Apophis were obtained. The average colors of Apophis during our observations were as follows: g ′ − r ′ = 0.618 ± 0.021 and r ′ − i ′ = 0.180 ± 0.021. No significant color variation was observed in r ′ − i ′, but a slight variation may have occurred in g ′ − r ′ during the observation period of 4.63 hr. The obtained colors appeared to match those of an Sq-class asteroid, which is the asteroid type previously determined for Apophis by Binzel et al. (2009 , Icarus, 200, 480) using the visible to near-infrared (0.55–2.45 μm) reflectance spectrum. [ABSTRACT FROM AUTHOR]

Oxygen‐sensitive and near‐infrared (NIR) luminescent YbIII coordination polymers incorporating ligands based on pyrene derivatives were synthesized: YbIII–TBAPy and YbIII–TIAPy (TBAPy: 1,3,6,8‐tetrakis(p‐benzoate)pyrene; TIAPy: 1,3,6,8‐tetrakis(3,5‐isophthalic acid)pyrene). The coordination structures of these materials have been characterized by means of electrospray ionization mass spectrometry, X‐ray diffraction analysis, and thermogravimetric analysis. Moreover, the porous structure of YbIII–TIAPy has been evaluated by measuring its N2 adsorption isotherm. The NIR luminescence properties of YbIII–TBAPy and YbIII–TIAPy have been examined by acquiring emission spectra and determining emission lifetimes under air or argon and in vacuo. YbIII–TIAPy exhibited high thermal stability (with a decomposition temperature of 400 °C), intense luminescence (with an emission quantum yield under argon of 6.6 %), and effective oxygen‐sensing characteristics. These results suggest that NIR luminescent YbIII coordination polymers prepared using pyrene derivatives could have applications in novel thermo‐stable oxygen sensors. [ABSTRACT FROM AUTHOR]

The Tsenkher structure in the Gobi-Altai, Mongolia is a c. 3.7 km diameter crater with a well-preserved ejecta blanket. It has been hypothesized to be either of impact or volcanic origin in our previous work. Observations during our 2007 expedition and related sample analyses give further support for an impact origin. The evidence includes the presence of a structurally uplifted near-circular rim surrounded by an ejecta blanket, and abundant breccias, some of which are melt- and millimetre-scale spherule-bearing. Planar deformation features (PDFs) were found in one quartz grain in a breccia sample. Fe-rich grains are found in a vesicular melt sample that is also characterized by elevated platinum group element (PGE) abundances with respect to the sedimentary bedrock of the area (approximately an order of magnitude). Noble gas analysis of one breccia sample yielded an elevated 3He/4He value of (5.0±0.2) × 10−6. Although not conclusive alone, these geochemical results are consistent with a contribution of meteoritic components. A volcanic origin, in particular a maar formation, would require explanations for the unusual conditions associated with Tsenkher, including its large size occurring in isolation, the structurally uplifted rim and the lack of a bedded base surge deposit. A pronounced rampart structure observed at the eastern ejecta is also unusual for any volcanic origin. 40Ar–39Ar dating of a vesicular melt sample gives an age of the Tsenkher structure of 4.9±0.9 Ma. The rampart structure could provide insights into the formation of similar ejecta morphologies associated with numerous impact craters on Mars. [ABSTRACT FROM AUTHOR]