Catastrophic Disruption Research Articles

Asteroid families: properties, recent advances, and future opportunities

Collisions are one of the key processes shaping planetary systems. Asteroid families are outcomes of such collision still identifiable across our solar system. The families provide a unique view of catastrophic disruption phenomena and have been in the focus of planetary scientists for more than a century. Most of them are located in the main belt, a ring of asteroids between Mars and Jupiter. Here we review the basic properties of the families, discuss some recent advances, and anticipate future challenges. This review pays more attention to dynamic aspects such as family identification, age determination, and long-term evolution. The text, however, goes beyond that. Especially, we cover the details of young families that see the major advances in the last years, and we anticipate it will develop even faster in the future. We also discuss the relevance of asteroid families for water-ice content in the asteroid belt and our current knowledge on links between families and main-belt comets. query Please check the edit made in the article title.

Schwann cell nodal membrane disruption triggers bystander axonal degeneration in a Guillain-Barré syndrome mouse model.

In Guillain-Barré syndrome (GBS), both axonal and demyelinating variants can be mediated by complement-fixing anti–GM1 ganglioside autoantibodies that target peripheral nerve axonal and Schwann cell (SC) membranes, respectively. Critically, the extent of axonal degeneration in both variants dictates long-term outcome. The differing pathomechanisms underlying direct axonal injury and the secondary bystander axonal degeneration following SC injury are unresolved. To investigate this, we generated glycosyltransferase-disrupted transgenic mice that express GM1 ganglioside either exclusively in neurons [GalNAcT–/–-Tg(neuronal)] or glia [GalNAcT–/–-Tg(glial)], thereby allowing anti-GM1 antibodies to solely target GM1 in either axonal or SC membranes, respectively. Myelinated-axon integrity in distal motor nerves was studied in transgenic mice exposed to anti-GM1 antibody and complement in ex vivo and in vivo injury paradigms. Axonal targeting induced catastrophic acute axonal disruption, as expected. When mice with GM1 in SC membranes were targeted, acute disruption of perisynaptic glia and SC membranes at nodes of Ranvier (NoRs) occurred. Following glial injury, axonal disruption at NoRs also developed subacutely, progressing to secondary axonal degeneration. These models differentiate the distinctly different axonopathic pathways under axonal and glial membrane targeting conditions, and provide insights into primary and secondary axonal injury, currently a major unsolved area in GBS research.

Review of the Book «Synthesis of Systems of Train Traffic Control at Railway Stations Eliminating Dangerous Failures»

The article provides a short review of the just published book by Professor Vl. V. Sapozhnikov entitled «Synthesis of Systems of Train Traffic Control at Railway Stations Eliminating Dangerous Failures». The book covers the basics of the synthesis of safety train traffic control systems at railway stations. Control systems at the stage of abstract synthesis are represented in the form of a set of multitudes of finite state machines, the implementation of which excludes the conditions for occurrence of dangerous failures and, accordingly, for occurrence of catastrophic disruptions in work, causing threats to passengers and transported goods. The book is recommended to developers of systems of control of responsible technological processes, computer-aided design systems, testing, technical diagnostics and monitoring of automation devices in transport and industry, as well as to the students, Ph.D. students, academia, specialists in the field of synthesis of control systems.

Forming iron-rich planets with giant impacts

ABSTRACT We investigate mantle stripping giant impacts (GI) between super-Earths with masses between 1 and $20\, {\rm M}_{\oplus }$. We infer new scaling laws for the mass of the largest fragment and its iron mass fraction, as well as updated fitting coefficients for the critical specific impact energy for catastrophic disruption, $Q_{{\rm RD}}^{*}$. With these scaling laws, we derive equations that relate the impact conditions, i.e. target mass, impact velocity, and impactor-to-target mass ratio, to the mass and iron mass fraction of the largest fragment. This allows one to predict collision outcomes without performing a large suite of simulations. Using these equations we present the maximum and minimum planetary iron mass fraction as a result of collisional stripping of its mantle for a given range of impact conditions. We also infer the radius for a given mass and composition using interior structure models and compare our results to observations of metal-rich exoplanets. We find good agreement between the data and the simulated planets suggesting that GI could have played a key role in their formation. Furthermore, using our scaling laws we can further constrain the impact conditions that favour their masses and compositions. Finally, we present a flexible and easy-to-use tool that allows one to predict mass and composition of a planet after a GI for an arbitrary range of impact conditions, which, in turn, allows to assess the role of GI in observed planetary systems.

Catastrophic disruption by hypervelocity impact of multi-layered spherical ice targets

The catastrophic disruption of tri-layered spherical icy bodies is reported. The bodies are 19 cm in total diameter, with a central core, an intermediate water layer and an icy surface (each layer respectively approximately 25, 55 and 20% of the total radius). Their response to high-speed impact is investigated at laboratory scales by firing 1.5 mm diameter glass spheres at the targets at speeds in the range 0.9 – 3.2 km s−1 and an ice layer thickness normalised to projectile diameter of typically 20 – 30. The energy density to just break apart such a body (defined as an event where the mass of the largest fragment post-impact is ½ the original target mass) is (3.1±0.1) J kg−1. This is significantly less than that found for similar sized solid ice spheres (18 ± 0.7) J kg−1, water filled ice spheres (16.25 ± 1.35) J kg−1 or hollow ice spheres (25.5 ± 0.5) J kg−1 indicating that the presence of a solid layer beneath an internal ocean, can influence disruption, effectively weakening the body.

Global-scale Reshaping and Resurfacing of Asteroids by Small-scale Impacts, with Applications to the DART and Hera Missions

We use a novel approach to model the entire cratering process resulting from impacts on small, weak asteroids that uses shock physics code calculations directly. We found that small-scale impacts (with a projectile size less than 1/150 of the target size) can significantly deform weak asteroids, causing global resurfacing at the same time. As a result, the collisional lifetime of the overall asteroid shapes is significantly lower than the traditionally used lifetime based on catastrophic disruption events. We also show that even very low asteroid cohesions can drastically influence the outcome of an impact. Consequently, if the target is homogeneous and weaker than ≈10 Pa, then NASA’s Double Asteroid Redirection Test impact on Dimorphos may not lead to a cratering event, as originally anticipated. Rather, the impact may change the global morphology of the asteroid. Our results, together with future observations by the ESA’s Hera mission, will provide constraints regarding the evolution of the shapes and structures of small asteroids by subcatastrophic impacts.

SPH simulations of high-speed collisions between asteroids and comets

We studied impact processes by means of smoothed-particle hydrodynamics (SPH) simulations. The method was applied to modelling formation of main-belt families during the cometary bombardment (either early or late, ∼3.85Gy ago). If asteroids were bombarded by comets, as predicted by the Nice model, hundreds of asteroid families (catastrophic disruptions of diameter D≥100km bodies) should have been created, but the observed number is only 20. Therefore we computed a standard set of 125 simulations of collisions between representative D=100km asteroids and high-speed icy projectiles (comets), in the range 8 to 15km/s. According to our results, the largest remnant mass Mlr is similar as in low-speed collisions, due to appropriate scaling with the effective strength Qeff, but the largest fragment mass Mlf exhibits systematic differences — it is typically smaller for craterings and bigger for super-catastrophic events. This trend does not, however, explain the non-existence of old families. The respective parametric relations can be used in other statistical (Monte-Carlo) models to better understand collisions between asteroidal and cometary populations.

Atmosphere loss in oblique Super-Earth collisions

ABSTRACT Using smoothed particle hydrodynamics we model giant impacts of Super-Earth mass rocky planets between an atmosphere-less projectile and an atmosphere-rich target. In this work, we present results from head-on to grazing collisions. The results of the simulations fall into two broad categories: (1) one main post-collision remnant containing material from target and projectile; (2) two main post-collision remnants resulting from ‘erosive hit-and-run’ collisions. All collisions removed at least some of the target atmosphere, in contrast to the idealized hit-and-run definition in which the target mass is unchanged. We find that the boundary between ‘hit-and-run’ collisions and collisions that result in the projectile and target accreting/merging to be strongly correlated with the mutual escape velocity at the predicted point of closest approach. Our work shows that it is very unlikely for a single giant impact to remove all of the atmosphere. For all the atmosphere to be removed, head-on impacts require roughly the energy of catastrophic disruption (i.e. permanent ejection of half the total system mass) and result in significant erosion of the mantle. We show that higher impact angle collisions, which are more common, are less efficient at atmosphere removal than head-on collisions. Therefore, single collisions that remove all the atmosphere without substantially disrupting the planet are not expected during planet formation.

Three-axial shape distributions of pebbles, cobbles and boulders smaller than a few meters on asteroid Ryugu

Over a broad size range, the shapes of impact fragments from catastrophic disruptions are distributed around the mean axial ratio 2: √2: 1, irrespective of experimental conditions and target materials. Although most blocks on asteroids are likely to be impact fragments, there is not enough quantitative data for reliable statistics on their three-axial lengths and/or ratios because it is difficult to precisely estimate the heights of the blocks. In this study, we evaluate the heights of blocks on asteroid Ryugu by measuring their shadows. The three-axial ratios of ~4100 small blocks with diameters from 5.0 cm to 7.6 m in Ryugu's equatorial region are investigated using eight close-up images of narrower localities taken at altitudes below 500 m, i.e. at <5.4 cm/pixel resolution, obtained immediately before the second touch-down of the Hayabusa2 spacecraft. The purpose of this study is to investigate the block shape distribution, which is important for understanding the geological history of asteroid Ryugu. Specifically, the shape distribution is compared to laboratory impact fragments. Our observations indicate that the shape distributions of blocks smaller than 1 m on Ryugu are consistent with laboratory impact fragment shape distributions, implying that the dominant shape-determining process for blocks on Ryugu was impact fragmentation. Blocks several meters in size in the equatorial region seem to be slightly flatter than the rest, suggesting that some blocks are partly buried in a bed of regolith. In conclusion, the shape distributions of blocks from several-cm to several-m in the equatorial region of asteroid Ryugu suggest that these are mainly fragments originating from the catastrophic disruption of their parent body and/or from a later impact.

A survey on Hungaria asteroids involved in mean motion resonances with Mars

Context. A region at the inner edge of the main asteroid belt is populated by the Hungaria asteroids. Among these objects, the Hungaria family formed as the result of a catastrophic disruption of the (434) Hungaria asteroid a few hundred million years ago. Due to the Yarkovsky effect, the fragments depending on their direction of rotation are slowly drifting inwards or outwards from the actual place of collision. Due to this slow drift, these bodies could approach the locations of the various outer-type mean-motion resonances (MMRs) with Mars. Aims. We aim to study the actual dynamical structure of Hungaria asteroids, which is primarily shaped by various outer-type MMRs with Mars. Moreover, we also seek connections between the orbital characteristics of Hungaria asteroids and their absolute magnitude. Methods. To map the resonant structure and dynamics of asteroids belonging to the Hungaria group, we used the FAst Identification of mean motion Resonances method, which can detect MMRs without the a priori knowledge of the critical argument. We also compiled stability maps of the regions around the MMRs by using the maximal variations in the asteroids’ eccentricities, semi-major axes, and inclinations. We numerically integrated the orbits of all asteroids belonging to the Hungaria group available in the JPL Horizon database together with the Solar System planets for one and ten million years. Results. Having studied the resonant structure of the Hungaria group, we find that several asteroids are involved in various MMRs with Mars. We identify both short- and long-term MMRs. Besides this, we also find a relationship between the absolute magnitude of asteroids and the MMR in which they are involved.

Dispersion and shattering strength of rocky and frozen planetesimals studied by laboratory experiments and numerical simulations

We have developed a method to investigate the whole mass–velocity distribution of impact fragments generated by catastrophic disruption of simulated planetesimals. Flash X-ray radiography including 12 iron particles for tracers was used to visualize the interior of the target, and the velocity distribution of the whole target was estimated by using the velocities of the tracers measured by X-ray images. High-velocity impact experiments in the laboratory and numerical simulations were conducted for four types of targets simulating rocky and frozen planetesimals at various specific energies, Q. These targets consisted of frozen clays with three different water contents ranging from 25 to 45 wt% and porous gypsum with a porosity of 51%. The shattering strength, QS*, and the mass–velocity distribution (MVD) were studied for these targets. The QS* of the frozen clays varied by a factor of 3–4 times, depending on the water content, and the QS* for porous gypsum was almost the same as that for the frozen clays with lower water contents. The numerical impact simulations led to slightly different QS* and MVD values for the frozen clay targets, possibly because of the partly ductile behavior of these samples. The MVDs resulting from the porous gypsum targets were well reproduced in the simulations. The cumulative mass of fragments with an ejection velocity slower than a specific velocity was examined to introduce a median velocity, v⁎, charactering the mass–velocity distribution. The v⁎ is defined as the velocity at which the cumulative mass corresponds to a half of the original target mass in the distribution. The v⁎ values of the frozen clays were described by the empirical equation v∗ = εQγ with almost the same ε and γ, irrespective of the water content, but the v⁎ of porous gypsum was about 1/3 that of the frozen clays. These experimental results were well reproduced by the numerical simulations for both frozen clays and porous gypsum targets. The dispersion strength, QD*, could be derived by comparing v⁎ with the escape velocity, vesc, of a target body with an effective mass, M, and radius, R. From this, a semi-theoretical equation showing the dispersion strength was derived: QD∗=1ε2GMR1/21/γ. Numerical simulations of catastrophic disruptions including self-gravity were conducted to directly determine QD* at large scale. These calculations showed that the effective mass of the target body, which is used in the computation of vesc = v⁎, should be a half of the original target mass, M = Mtarget /2. Our results suggest that this approach for computing the semi-theoretical dispersion strength is suitable for bodies larger than ~10 km.

Guest Editorial: Student Success in a Global Pandemic

The catastrophic disruption to higher education from the COVID-19 pandemic has brought about significant and rapid changes to the delivery of mainstream teaching and learning in higher education institutions around the globe, in particular through the use of online learning. The many examples of innovation and novelty demonstrated by institutions and individuals in their support of students and their learning provides a timely opportunity for the sharing of exemplary activities and outcomes in the Student Success Journal. We are pleased to announce that Student Success in a Global Pandemic has been chosen as the topic for the 2021 Special Issue to enable academics, practitioners, leaders and policy makers to share their stories and outcomes and have ongoing learning from a time of extraordinary innovation.

The young Hobson family: Possible binary parent body and low-velocity dispersal

Context.Asteroid families with ages younger than 1 Myr offer an interesting possibility of studying the outcomes of asteroid disruptions that are little modified by subsequent evolutionary processes.Aims.We analyze a very young asteroid family associated with (18777) Hobson in the central part of the main belt. We aim at (i) understanding its peculiar size distribution, and (ii) setting an upper limit on the characteristic dispersal velocity at subkilometer sizes corresponding to the smallest visible Hobson members.Methods.We identified the Hobson family using an up-to-date asteroid catalog. A significant increase in the number of its known members allowed us to study their size distribution and compare it with computer simulations of catastrophic disruptions. Backward orbital integrations of the heliocentric orbits allowed us to confirm the previously suggested age of Hobson and helped to estimate limits of the ejection speed.Results.The Hobson family has an unusual size distribution: two nearly equal-size bodies, followed by a population of smaller asteroids, whose distribution takes a characteristic power law. There are two possibilities to explain these data. Either a canonical impact onto a single parent body, requiring fine-tuned impact conditions that have not been studied so far, or an unconventional model for the parent object of the Hobson family, namely a binary with ≃7−9 km primary and a ≃2.5 km secondary. In the latter case, the primary was disrupted, leaving behind the largest remnant (18777) Hobson and a suite of subkilometer asteroids. The second largest asteroid, (57738) 2001 UZ160, is the nearly intact satellite of the parent binary. The excellent convergence of nominal orbits of Hobson members sets an upper limit of ≃(10−20) m s−1for the initial dispersal velocity of the known members, which is consistent with both formation models. The Hobson family provides a so far rare opportunity of studying disruptions of small asteroids in a situation in which both the material strength and reaccumulation efficiency play an important role.

On the origin of the Kreutz family of sungrazing comets

ABSTRACT We evaluate numerically three different models for the parent comet of the Kreutz family of sungrazers: (i) A Centaur on a highly inclined or retrograde orbit that diffuse to the inner planetary region where it became a sungrazer (Model 1). (ii) A parent comet injected from the Oort cloud straight into a near-parabolic, sungrazing orbit. Near perihelion the comet was disrupted by tidal forces from the Sun giving rise to a myriad of fragments that created the Kreutz family (Model 2). (iii) A two-step process by which an Oort cloud comet is first injected in a non-sungrazing, Earth-crossing orbit where its semimajor axis decreases from typical Oort cloud values (a ∼ 104 au) to around 102 au, and then it evolves to a sungrazing orbit by the Lidov–Kozai mechanism (Model 3). Model 1 fails to produce sungrazers of the Kreutz type. Model 2 produces some Kreutz sungrazers and has the appeal of being the most straightforward. Yet the impulses received by the fragments originated in the catastrophic disruption of the parent comet will tend to acquire a wide range of orbital energies or periods (from short-period to long-period orbits) that is in contradiction with the observations. Model 3 seems to be the most promising one since it leads to the generation of some sungrazers of the Kreutz type and, particularly, it reproduces the clustering of the argument of perihelion ω of the observed Kreutz family members around 60°–90°, as a natural consequence of the action of the Lidov–Kozai mechanism.

Spatial-Temporal Patterns of Air Pollutant Emissions From Landing and Take-Off Cycles in the Yangtze River Delta of China During the COVID-19 Outbreak.

The global aviation industry has been experiencing catastrophic disruption since the beginning of 2020 due to the unprecedented impact of the COVID-19 pandemic on air traffic. Although the decline in regular commercial air travel has caused tremendous economic loss to aviation stakeholders, it has also led to the reduction in the amount of recorded air pollutants. Most of the aircraft emissions are released during the cruise phase of flight, however they have relatively small impact on humans due to the fact that those emissions are released directly into the upper troposphere and lower stratosphere. Therefore, the scope of this study is to investigate the ground-level aircraft emissions from landing and take-off (LTO) cycles, as they have a greater influence on the ambient environment of the airports in a specific region. In this paper, we study the variation of typical air pollutant concentrations (i.e., HC, CO, and NOx) from the LTO cycles during the outbreak of COVID-19 pandemic in both temporal and spatial scales. These ground-level emissions are estimated for the 22 airports in the Yangtze River Delta, China. The results indicate that the variation pattern of the three air pollutants were significantly influenced by the dramatic onset of the COVID-19 pandemic, as well as the pertinent policies to suppress the spread of the virus. The results also reveal non-uniform distribution of the emission quantified at different airports. It is noticeable that the emission quantity generally declined from the east coast to the central and western part of the research region. Furthermore, discrepancies in the target markets also create disparities in the variation pattern of the emissions at different airports under the context of COVID-19.

Maternal Diabetes and Infant Sex Ratio.

Evolutionary hypotheses on the ratio of males to females at birth posit that women terminate pregnancies with low likelihood of surviving and producing grandchildren. Thus, females are preferred to males under unfavorable conditions. Much of this literature has focused on catastrophic disruptions that induce maternal stress and result in fewer males. Diabetes may similarly affect the sex ratio. A male bias at birth among infants born to women with GDM is widely recognized; mild hyperglycemia experienced early in pregnancy may signal favorable conditions and warrant investment in males. There are sparse data on women with pregestational diabetes, but some evidence for a female bias born to those with type 1 diabetes and severe hyperglycemia (i.e., requiring insulin). Disease-related maternal stress in these women may lead to the selective termination of male fetuses. Further examination of pregestational diabetes stands to contribute to scientific understanding of the sex ratio.

Will Catastrophic Cyber-Risk Aggregation Thrive in the IoT Age? A Cautionary Economics Tale for (Re-)Insurers and Likes

Service liability interconnections among networked IT and IoT-driven service organizations create potential channels for cascading service disruptions due to modern cybercrimes such as DDoS, APT, and ransomware attacks. These attacks are known to inflict cascading catastrophic service disruptions worth billions of dollars across organizations and critical infrastructure around the globe. Cyber-insurance is a risk management mechanism that is gaining increasing industry popularity to cover client (organization) risks after a cyber-attack. However, there is a certain likelihood that the nature of a successful attack is of such magnitude that an organizational client’s insurance provider is not able to cover the multi-party aggregate losses incurred upon itself by its clients and their descendants in the supply chain, thereby needing to re-insure itself via other cyber-insurance firms. To this end, one question worth investigating in the first place is whether an ecosystem comprising a set of profit-minded cyber-insurance companies, each capable of providing re-insurance services for a service-networked IT environment, is economically feasible to cover the aggregate cyber-losses arising due to a cyber-attack. Our study focuses on an empirically interesting case of extreme heavy tailed cyber-risk distributions that might be presenting themselves to cyber-insurance firms in the modern Internet age in the form of catastrophic service disruptions, and could be a possible standard risk distribution to deal with in the near IoT age. Surprisingly, as a negative result for society in the event of such catastrophes, we prove via a game-theoretic analysis that it may not be economically incentive compatible , even under i.i.d. statistical conditions on catastrophic cyber-risk distributions, for limited liability-taking risk-averse cyber-insurance companies to offer cyber re-insurance solutions despite the existence of large enough market capacity to achieve full cyber-risk sharing. However, our analysis theoretically endorses the popular opinion that spreading i.i.d. cyber-risks that are not catastrophic is an effective practice for aggregate cyber-risk managers, a result established theoretically and empirically in the past. A failure to achieve a working re-insurance market in critically demanding situations after catastrophic cyber-risk events strongly calls for centralized government regulatory action/intervention to promote risk sharing through re-insurance activities for the benefit of service-networked societies in the IoT age.

The EOS/resolution conspiracy: convergence in proto-planetary collision simulations

ABSTRACT We investigate how the choice of equation of state (EOS) and resolution conspire to affect the outcomes of giant impact (GI) simulations. We focus on the simple case of equal-mass collisions of two Earth-like 0.5-M⊕ proto-planets showing that the choice of EOS has a profound impact on the outcome of such collisions as well as on the numerical convergence with resolution. In simulations where the Tillotson EOS is used, impacts generate an excess amount of vapour due to the lack of a thermodynamically consistent treatment of phase transitions and mixtures. In oblique collisions this enhances the artificial angular momentum (AM) transport from the planet to the circum-planetary disc reducing the planet’s rotation period over time. Even at a resolution of 1.3 × 106 particles, the result is not converged. In head-on collisions, the lack of a proper treatment of the solid/liquid-vapour phase transition allows the bound material to expand to very low densities, which, in turn, results in very slow numerical convergence of the critical specific impact energy for catastrophic disruption $Q_{\rm {RD}}^{*}$ with increasing resolution as reported in prior work. The simulations where ANalytic Equation Of State (ANEOS) is used for oblique impacts are already converged at a modest resolution of 105 particles, while head-on collisions converge when they evidence the post-shock formation of a dense iron-rich ring, which promotes gravitational re-accumulation of material. Once sufficient resolution is reached to resolve the liquid-vapour phase transition of iron in the ANEOS case, and this ring is resolved, the value of $Q_{\rm {RD}}^{*}$ has then converged.

Catastrophic supply chain disruptions and supply network changes: a study of the 2011 Japanese earthquake

PurposeCatastrophic supply chain disruptions can significantly damage the operational and financial performance of firms. While a growing body of literature on supply network structures has studied what influences supply networks' vulnerability to supply chain disruptions and capability to recover from them, it remains unclear how supply network structures change after major supply chain disruptions. We aim to provide an understanding of how these changes occur.Design/methodology/approachUsing a natural experiment approach and supply network data from Factset, this study investigates how firms' supply network structures change after experiencing the catastrophic supply chain disruptions caused by the 2011 Tohoku earthquake and tsunami in Japan. We capture post-earthquake supply network changes using the measures of degree centrality and ego network density.FindingsThe results of the analysis suggest that compared to unaffected firms, the affected firms experience changes in their supply network structures tending toward lower complexity measured by in-degree centrality, out-degree centrality and ego network density.Originality/valueThis study contributes to social network theory and the complex adaptive supply network literature by providing empirical evidence of structural changes in supply networks after catastrophic supply chain disruptions. A managerial contribution is made by providing a reflection on why these changes might be occurring and alert firms to the challenges of managing complexity in their supply networks.

High-resolution observations of bright boulders on asteroid Ryugu: 1. Size frequency distribution and morphology

The near-Earth asteroid (162173) Ryugu displays a Cb-type average spectrum and a very low average normal albedo of 0.04. Although the majority of boulders on Ryugu have reflectance spectra and albedo similar to the Ryugu average, a small fraction of boulders exhibit anomalously high albedo and distinctively different spectra. A previous study (Tatsumi et al., 2021Nature Astronomy, 5, doi:https://doi.org/10.1038/s41550-020-1179-z) based on the 2.7-km observations and a series of low-altitude (down to 68 m) descent observations conducted prior to the first touchdown have shown that the spectra of these anomalous boulders can be classified into two distinct groups corresponding to S and C type asteroids. The former originate most likely from an impactor that collided with Ryugu's parent body, whereas the latter may be from portions of Ryugu's parent body that experienced a different temperature history than experienced by the majority of boulder materials. In this study, we analyzed images captured after the first touchdown to determine the quantitative properties of these bright boulders on Ryugu. We measured the sizes of more than a thousand bright boulders and characterized the morphologic properties of the largest ones. Analyses revealed many properties of bright boulders important for the evolution of Ryugu and its parent body. First, the size–frequency distributions of S-type and C-type bright boulders follow a power law with exponents of 1.6 ± 1.3 and 3.0 ± 0.7, respectively. Based on these size–frequency distributions, we obtained the ratios of the total volume and surface area of S-type bright boulders to those of average dark boulders on the Ryugu's surface, that is, 7.1−5.0+6.3 × 10−6 and 1.5−1.2+3.2 × 10−6, respectively, over the diameter range of 0.3 to 3 m. Similarly, the ratio of the total volume and surface area of C-type bright boulders to those of average dark boulders are 4.4−2.2+14.0 × 10−5 and 1.3−1.1+9.8 × 10−3, respectively, at a diameter range of 2 cm to 2 m. Second, the number density of bright boulders inside the artificial crater newly made by the Small Carry-on Impactor (SCI) experiment agrees with the outside number density within a factor of two. Third, many of the bright boulders are embedded in a larger substrate boulder, suggesting that they have experienced mixing and conglomeration with darker fragments on Ryugu's parent body, rather than gently landing on Ryugu during or after its formation by reaccumulation. This observation is consistent with the hypothesis that S-type bright boulders were likely mixed during and/or before a catastrophic disruption. C-type bright boulders embedded in substrate boulders suggests a brecciation process after thermal metamorphism. Furthermore, the embedding of S-type clasts in substrate boulders suggests that brecciation did indeed occur even after a large-scale impact on the parent body. If the brecciation on the Ryugu's parent body occurred over such a long period or over many stages of its evolution, breccias may end up being the dominant constituent materials on Ryugu's parent body. Moreover, the preponderance of breccias may contribute to the globally low thermal inertia of Ryugu.