The Hayabusa2 spacecraft investigated the small asteroid Ryugu, which has a rubble-pile structure. We describe an impact experiment on Ryugu using Hayabusa2's Small Carry-on Impactor. The impact ...produced an artificial crater with a diameter >10 meters, which has a semicircular shape, an elevated rim, and a central pit. Images of the impact and resulting ejecta were recorded by the Deployable CAMera 3 for >8 minutes, showing the growth of an ejecta curtain (the outer edge of the ejecta) and deposition of ejecta onto the surface. The ejecta curtain was asymmetric and heterogeneous and it never fully detached from the surface. The crater formed in the gravity-dominated regime; in other words, crater growth was limited by gravity not surface strength. We discuss implications for Ryugu's surface age.
Context.
The Hayabusa2 spacecraft launched by Japan Aerospace Exploration Agency has been conducting observations of the asteroid (162173) Ryugu since June 2018. The Telescopic Optical Navigation ...Camera (ONC-T) onboard Hayabusa2 has obtained thousands of images under a variety of illumination and viewing conditions.
Aims.
Our objective is to examine and validate the camera calibration, derive a photometric correction for creating global albedo maps, and to interpret the photometric modeling results to characterize the surface of Ryugu.
Methods.
We observed (162173) Ryugu with the Gemini-South telescope, and combined these measurements with other published ground-based observations of the asteroid. The ground-based observations were compared with the data obtained by ONC-T in order to validate the radiometric calibration mutually. We used a combination of the Hapke disk-integrated and disk-resolved model equations to simultaneously analyze the combined ground- and spacecraft-based data.
Results.
The average spectrum of Ryugu was classified as Cb-type following the SMASSII taxonomy and C/F-type following the Tholen taxonomy based on spacecraft observations. We derived Hapke model parameters for all seven color filters, which allowed us to photometrically correct images to within an error of <10% for ~80% of the image pixels used in the modeling effort. Using this model, we derived a geometric albedo of 4.0 ± 0.5% (
v
band) for Ryugu. The average reflectance factor at the standard illumination condition was 1.87 ± 0.14% in the
v
band. Moreover we measured a phase reddening of (2.0 ± 0.7) × 10
−3
μ
m
−1
deg
−1
for Ryugu, similar to that observed for the asteroid (101955) Bennu.
Conclusions.
The global color map showed that the general trend was for darker regions to also be redder regions, however there were some distinct exceptions to this trend. For example, Otohime Saxum was bright and red while Kibidango crater was dark and blue. The darkness and flatness of Ryugu’s reflectance might be caused by a high abundance of organic materials.
In Fukushima Prefecture, disaster-related death is a social problem for individuals who were forced to leave their hometowns as a result of the Great East Japan Earthquake and the accident at ...Fukushima Daiichi nuclear power plant. Disaster-related death is caused by stress, exhaustion, and worsening of pre-existing illnesses due to evacuation. The number of disaster-related deaths has reached almost 2000, and continues to rise. Prolonged uncertainty and deteriorating living conditions suggest no end to such deaths, although response measures have been taken to improve the situation. It is said that insufficient response measures were taken, in particular, during the transitional period between the emergency phase and the reconstruction phase. There is a need to apply the lessons learned in planning for evacuation after a nuclear hazard, considering radiological protection as well as risks associated with evacuation.
A projectile accelerated by the Hayabusa2 Small Carry-on Impactor successfully produced an artificial impact crater with a final apparent diameter of 14.5 ± 0.8 m on the surface of the near-Earth ...asteroid 162173 Ryugu on April 5, 2019. At the time of cratering, Deployable Camera 3 took clear time-lapse images of the ejecta curtain, an assemblage of ejected particles forming a curtain-like structure emerging from the crater. Focusing on the optical depth of the ejecta curtain and comparing it with a theoretical model, we infer the size of the ejecta particles. As a result, the typical size of the ejecta particles is estimated to be several centimeters to decimeters, although it slightly depends on the assumed size distribution. Since the ejecta particles are expected to come from a depth down to ~1 m, our result suggests that the subsurface layer of Ryugu is composed of relatively small particles compared to the uppermost layer on which we observe many meter-sized boulders. Our result also suggests a deficit of particles of less than ~1 mm in the subsurface layer. These findings will play a key role in revealing the formation and surface evolution process of Ryugu and other small Solar System bodies.
The purpose of this study was to investigate the effect of salt substitutes on the textural, microstructural and sensory properties in low-cost frankfurter sausages produced using mechanically ...deboned poultry meat (MDPM) as a potential strategy to reduce sodium in this meat product. In nine treatments, blends of calcium, sodium and potassium chloride were used to substitute 25% or 50% of the NaCl in sausages (at the same ionic strength and molar basis equivalent to 2% NaCl). When NaCl was partially replaced by 50% CaCl2 (F6), the batter presented the highest total liquid released, and the corresponding final product showed increased hardness when compared to the control formulation (100% NaCl, C1). Its respective microstructural analysis revealed numerous pores arranged in a noncompacted matrix, which could be explained by the lowest emulsion stability reported for samples with 50% CaCl2 and 50% NaCl. Frankfurter sausages produced using blends containing 25% CaCl2 (F2, F4) and 25 and 50% KCl (F4, F5) did not exhibit differences in the pH, aw and objective color in the frankfurters (p<0.05). The overall acceptability and flavor of the frankfurters containing 50% NaCl without salt substitution (C3), 25% CaCl2, 25% KCl (F4), and 50% KCl (F5) showed the worst scores compared to those of the control formulation (C1). These results may be useful to select salt blends containing KCl, CaCl2 and NaCl to reduce the sodium in sausages containing high concentrations of MPDM at an ionic equivalent strength to the NaCl commonly used in traditional formulations.
•NaCl was partially replaced by KCl or CaCl2 to reduce Na in frankfurters.•CaCl2 decreases the emulsion stability and the texture of low Na frankfurters.•Blends of 25% CaCl2 and 25% KCl can substitute 50% NaCl in frankfurters.•Blends of 50% KCl and 50% NaCl do not change the textural properties of frankfurters.
Hayabusa2
is a sample return mission of JAXA launched on 3 December 2014.
Hayabusa2
is the successor of
Hayabusa
, which returned samples from the asteroid Itokawa to the Earth. Although the design ...of
Hayabusa2
follows that of
Hayabusa
, the former is equipped with some new components. The small carry-on impactor (SCI) is one of those components. The SCI is a compact kinetic impactor designed to remove the asteroid surface regolith locally and create an artificial crater. One of the most important scientific objectives of
Hayabusa2
is to investigate the chemical and physical properties of the internal materials and structures of the target body, asteroid Ryugu.
Hayabusa2
will attempt to observe the resultant crater with some scientific instruments and to get samples from around the crater. High kinetic energy is required to create a meaningful crater, however, the impact system design needs to fit within strict constraints. Complicated functions, such as a guidance and control system, are not permitted. A special type of shaped charge is used for the acceleration of the impactor of the SCI in order to make system simpler. Using this explosion technique makes it possible to accelerate the impactor very quickly and to hit the asteroid without a guidance system. However, the impact operation will be complicated because the explosive is very powerful and it scatters high-speed debris at the detonation. This paper describes an overview of the SCI system, the results of the development testing and an outline of the impact experiment of the
Hayabusa2
mission.
A wide variety of electromagnetic phenomena possibly related with earthquake (EQ) preparation processes have been reported in the literature during the last few decades. An interesting aspect in ...their study is the time series analysis of the related observables aiming at the investigation of any embedded dynamics. In this review article we focus on the study of fracto-electromagnetic emissions (fracto-EME) at the MHz band, the ultra-low frequency (ULF) magnetic field variations (<3 Hz) and the subionospheric very low frequency (VLF) propagation anomalies. We present recent analysis results for these electromagnetic signals using two independent methods which are known for their ability to uncover critical dynamics, the recently proposed method of critical fluctuations (MCF) and the natural time (NT) analysis method. Our results show that all three considered electromagnetic signals present critical characteristics from a few weeks up to a few days before the main shock occurrence. On the other hand, signatures for the departure from the critical (highly symmetrical) state towards a low symmetry state, a state during which there is high localization of the EQ preparatory process, have been identified in specific cases for the MHz fracto-EME as well as for the ULF magnetic field variations. Based on a multidisciplinary analysis, a four-stage model of EQ dynamics by means of fracto-EME in the MHz and kHz bands has recently been proposed. The hypothesis that the precursors considered in this article emerge during the spatially extensive phase of EQ preparation, which corresponds to the first stage of the abovementioned four-stage model, as well as their relation with the foreshock seismic activity are discussed.
The Small Carry-on Impactor (SCI) equipped on
Hayabusa2
was developed to produce an artificial impact crater on the primitive Near-Earth Asteroid (NEA) 162173 Ryugu (Ryugu) in order to explore the ...asteroid subsurface material unaffected by space weathering and thermal alteration by solar radiation. An exposed fresh surface by the impactor and/or the ejecta deposit excavated from the crater will be observed by remote sensing instruments, and a subsurface fresh sample of the asteroid will be collected there. The SCI impact experiment will be observed by a Deployable CAMera 3-D (DCAM3-D) at a distance of ∼1 km from the impact point, and the time evolution of the ejecta curtain will be observed by this camera to confirm the impact point on the asteroid surface. As a result of the observation of the ejecta curtain by DCAM3-D and the crater morphology by onboard cameras, the subsurface structure and the physical properties of the constituting materials will be derived from crater scaling laws. Moreover, the SCI experiment on Ryugu gives us a precious opportunity to clarify effects of microgravity on the cratering process and to validate numerical simulations and models of the cratering process.
The aim of this work is to study the relationship between the pre-earthquake emissions of radon and ULF/ELF (1–30 Hz) atmospheric electromagnetic radiation. The problem is considered on the example ...of the 2011 Tohoku earthquake. Radon, ionizing air, creates ions—centers of condensation of water vapor. As a result of condensation, heat is generated. It results in growth of air temperature and decrease in its humidity. This phenomenon serves as an indicator of air ionization. We used data from 20 Japan Meteorological Agency (JMA) weather stations located on Honshu Island to estimate any changes in temperature and humidity over ± 20 days from the date of the main shock. At the same time, we monitored the intensity and location of the source of ULF/ELF radiation using three induction magnetometers belonging to Chubu University. We compared the times and locations of observed signs of ionization and electromagnetic radiation to find out their relationship. It turned out that they are independent, since their dates and localizations do not match. In addition, we found intense ionization of the air after March 11 over a large area of Honshu Island, caused by radiative radiation from the nuclear disaster at the Fukushima Daiichi nuclear power plant. However, this phenomenon did not cause low-frequency atmospheric electromagnetic radiation either. These suggest that there is no direct relationship between air ionization and ULF/ELF radiation. This is true at least for this case, given the island nature of the land and oceanic EQs.
Images from the Optical Navigation Camera system (ONC) onboard the Hayabusa2 spacecraft show the MASCOT lander during its descent to the surface of asteroid (162173) Ryugu. We used results from a ...previous stereo-photogrammetric analysis that provided precise ONC image orientation data (camera position and pointing), ONC orthoimages, and an ONC-based 3D surface model to combine them with the visibilities of MASCOT itself and its shadow on-ground within the ONC images. We integrated additional information from instruments onboard MASCOT (MASMag, MARA, MASCam) and derived MASCOT’s release position and modeled its free-fall descent path and its velocity over 350 s from its release at ∼41 m altitude above ground until its first contact with the surface of Ryugu. After first contact, MASCOT bounced over the surface of Ryugu for 663 s and came to rest at its first settlement point after four intermediate surface contacts. We again used ONC images that show MASCOT and partly its shadow and reconstructed the bouncing path and the respective velocities of MASCOT. The achieved accuracy for the entire descent and bouncing path is ∼0.1 m (1σ).
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