Secondary mineral prevalence in Ryugu samples, similar to primitive carbonaceous-Ivuna type (CI) chondrites, suggests that aqueous alteration was a key factor in its formation. However, this general consensus masks our limited understanding of the specific mechanisms and environmental conditions involved in water-rock interactions on primitive asteroids. High-resolution cathodoluminescence (CL) analysis of the ubiquitous dolomite crystals in Ryugu samples reveals concentric epitaxial overgrowths with varying levels of Mn2+-activated luminescence. CL panchromatic images and spectral deconvolution provide compelling evidence for the evolution of aqueous fluids toward highly saturated brines. Given the close association of dolomite with widespread intergrowths of serpentine and saponite in the matrix, we propose that brine formation occurs as a byproduct of serpentinization. Unlike large-scale evaporation or freezing, this process can locally cause the hydrothermal fluid to dry out, significantly increasing its salinity over time. This leads to the sporadic precipitation of an evaporite mineral sequence, with dolomite forming at an early stage. This serpentinization-driven brine formation model offers a convincing alternative to a purely prograde alteration history for Ryugu. It may also provide a better explanation for the alteration processes of Bennu and other CI chondrite parent bodies.

The Hayabusa2 spacecraft successfully collected samples from two distinct locations on Ryugu, a C-type asteroid, and these samples were stored separately in sample containers in chambers A and C, respectively. Infrared absorption spectra were obtained using Fourier transform infrared (FTIR) microspectroscopy to provide characterization of the Ryugu particles and their organic matter as part of the organic macromolecule initial analysis team. The IR transmission (absorption) spectra of samples from both chambers A and C were nearly identical and consistent with CI chondrites. Some local heterogeneity was observed, such as areas where the IR spectra were dominated by carbonates. The average CH2/CH3 peak height ratio of Ryugu samples was 1.11 +/- 0.13, which is lower than that of the Ivuna CI chondrite (similar to 1.6). Furthermore, the CH2/CH3 ratio of Ryugu in this study was significantly lower than the previously reported values for Ryugu. To test the environmental effects, changes in the IR spectra were monitored during analyses and storage. Notably, approximately 15% increases in the aliphatic CH peak were observed during the FTIR analysis within similar to 1 h, when the measurement was conducted under ambient condition, partly due to the adsorption of environmental volatile organic compounds (VOCs), likely machine oil used in the FTIR instruments. However, the effects of VOCs on the CH2/CH3 ratio are not clear in this study. Measurements performed in a heating stage at a mild temperature of 60 degrees C with N-2 flow gave the best spectra, minimizing water and VOC contamination. Porous OH-bearing silicates are known to adsorb VOCs, particularly when fresh surfaces are exposed just after crushing the samples. The Ryugu samples appear to be significantly reactive, adsorbing VOCs very rapidly even in a clean environment with minimal contamination sources. The highly porous and fresh nature of Ryugu samples may be responsible for this behavior.

For millennia humans have pondered the question "Are we alone in the universe?" In recent decades the search for evidence of life beyond earth has focused on the search for habits in which liquid water is now or has in the past been present, as well as the search for organic molecules in extraterrestrial (ET) samples. These efforts have, in turn, spurred significant technological advances to develop methods to analyze fluid inclusions (FI) in ET materials, including meteorites and more recently ET samples collected and returned to earth by various missions that have visited a variety of planetary bodies. Some early reports of fluid inclusions in meteorites in the 1970s were later found to be artifacts introduced during sample preparation. As a result, the study of FI in extraterrestrial samples entered a dark period in which any reports of FI in meteorites were dismissed as likely representing fluids introduced after the samples reached earth. The study of FI in ET samples gained renewed interest following the discovery and documentation of aqueous FI in halite in the Monahans (1998) H5 chondrite. The halite and its contained FI were clearly present before the meteorite reached earth, and subsequent studies confirmed that the age of the halite and its contained FI was 4.7 ±0.2 Ga. This discovery spurred new interest to search for FI in meteorites, now using sample preparation methods that avoid introducing water or other fluids into the sample. In the last two decades much progress has been made in identifying FI in meteorites and mission returned samples, and there are now dozens of well documented reports of FI in these samples. The rarity of FI in ET samples, combined with the generally small size of the FI (less than approximately 1-2 microns in many cases), has led to efforts to develop and improve analytical techniques to characterize the FI. To this end, our group has determined the bulk chemical and H & O stable isotopic composition of individual FI in Zag and Monahans (1998) halite and asteroid Ryugu pyrrhotites using cryo-Time of Flight Secondary Ion Mass Spectrometry (cryo-TOF-SIMS). In this presentation we will summarize some of these recent efforts involving careful and sophisticated sample preparation and analysis methods.

Particles collected from the asteroid Ryugu by the Hayabusa2 spacecraft offer a unique opportunity to investigate the magnetic record of the primitive solar system, as any terrestrial magnetic contamination is minimal and can be accounted for. In previous studies, stepwise alternating field demagnetization (AFD) measurements of natural remanent magnetization (NRM) records have been conducted on seven Ryugu particles. However, due to the limited number of samples, there is no consensus regarding the interpretation of the results of these measurements. To address this problem, we performed stepwise AFD measurements of the NRM on 28 Ryugu particles. Twenty-three of the particles exhibited one or two stable NRM components, whereas the remaining five did not. Isothermal remanent magnetization-based paleointensity values derived from stable NRM components varied by more than one order of magnitude. These NRM characteristics were consistent with those observed in previous studies. Therefore, as a reflection of the original nature of the NRM record, some Ryugu particles exhibited stable NRM components, whereas others did not. The Ryugu particles investigated in this study and those from a previous study exhibited spatially inhomogeneous NRM directions within individual particles, constraining the NRM acquisition time to before the final solidification of the current Ryugu particles. A mechanism of remanence acquisition that can explain the observed NRM characteristics is a chemical remanent magnetization associated with the growth of framboidal magnetite during aqueous alteration in Ryugu's parent body.

Four carbonaceous chondrite (CC) meteorites - MET 00432, Tagish Lake, Tarda, and WIS 91600 - have been proposed to be members of a CC grouplet, hereafter termed the Carbonaceous Tagish Lake Grouplet (CTG). We investigated their possible affinities via a spectral reflectance-focused study of them, as chips and variously sized powders. We also considered possible spectrum-altering effects of space weathering and composition of the organic component on such red-sloped spectra. Ultraviolet-region spectra (200-400 nm) exhibit absorption features attributable to unspecific Fe2+-O and/or Fe3+-O charge transfers, possibly due to Fe-rich phyllosilicates. Both albedo and spectral slope vary as a function of grain size. The 0.35-2.50 mu m interval is characterized by dark, variably red-sloped spectra with low albedos in the visible region (<6% reflectance at 0.550 mu m). Spectral slopes are redder for powders than slabs or chips. CTG spectra also exhibit shallow (<4% deep) absorption bands attributable to known components, such as magnetite and phyllosilicates, particularly in the 1 mu m region. Spectral analysis of an extensive suite of phyllosilicate+opaque mixtures suggests that only a subset of CTG opaque components can cause darkening and overall red spectral slopes, in particular low H/C ratio carbonaceous compounds. Other opaque components, such as iron sulfides, magnetite and other carbonaceous materials, some of which are red-sloped when pure, cause spectral bluing or only slight spectral reddening. Albedo and spectral slopes and shapes are affected by physical properties, such as grain size, as well as the types, compositions, abundances, dispersion, and grain sizes of opaque components. At longer wavelengths (to 14 mu m), CTG spectra exhibit a number of absorption features that can be related to their silicate, carbonate, and organic components. A prominent absorption feature is present in the 2.7-3.1 mu m region attributable to phyllosilicates +/- H2O, some of which is likely attributable to terrestrial alteration. Petrological, mineralogical, and isotopic information provide support for these meteorites having strong affinities to each other and comprising a grouplet. Additional CTG meteorites may lurk among the many tens of CCs that have been incompletely characterized.

Surface processes on the asteroid Ryugu have been investigated using cosmic-ray-produced radionuclides, Be-10, Al-26, and Cl-36, and stable noble gases, on eight samples returned by the Hayabusa2 spacecraft. The Be-10 and Al-26 along with Ne-21 measurements indicate that the two Chamber A samples A0105 collected during the first touchdown (TD) were exposed to cosmic rays for similar to 6.8 Myr at a shielding depth of 4-15 g cm(-2). Beryllium-10 and Al-26 from Chamber C samples from the second TD site, close to the artificial crater, were ejected from shielding depths of 120-160 g cm(-2) for C0002, 20-85 g cm(-2) for C0106-09, and 120-155 g cm(-2) for C0106-10, -11, and -12, respectively. The exposure ages of these four C0106 samples differ, ranging from 1.7-8.8 Myr. These measurements provide unique and clear evidence that Hayabusa2 successfully collected subsurface samples ejected by an artificially produced crater. Chlorine-36 produced by secondary-produced thermal neutrons was observed in the samples, consistent with the high concentration of H and Cl. Helium (He) and Ne of solar wind origin were released at the lowest heating temperature of 200 degrees C during a stepwise pyrolysis.

Reflectance spectra from the surface of asteroid Ryugu, measured by the Hayabusa2 spacecraft, exhibit a metal-OH absorption at ∼2.7 μ m that is approximately half as deep as the returned samples measured in the laboratory and shifted toward longer wavelengths. These spectral differences likely result from the effects of space weathering; however, this interpretation has not been confirmed. In this study, we conducted a detailed observation of the surface of the Ryugu sample A0283, which shows reflectance spectra indicative of space weathering. Electron microscope observations on the A0283 surface identified space-weathering features (e.g., smooth and frothy layers and melt splashes) as previously reported. At these modified surfaces, the 2.7 μ m band was approximately 50% shallower than that from unweathered surfaces and the position shifted up to 8 nm longer wavelengths. Additionally, the Reststrahlen band of phyllosilicates at ∼10 μ m shifted by up to 0.8 μ m from the position of unweathered samples, and its peak broadened. In particular, the regions covered by the frothy layer exhibited significant spectral changes. The frothy layer consists of vesicular amorphous silicate, with a thickness of tens to thousands of nanometers, and exhibits a lower Mg/Fe atomic ratio than the interior. These results indicate that space weathering causes amorphization, dehydration, Mg sputtering of the asteroid surface, and consequently, modification of reflectance spectra of asteroid Ryugu. In contrast, the collected samples are dominated by newly exposed surfaces, resulting in the observed spectral differences between the asteroid surface and its returned samples.

In the Martian Moons eXploration (MMX) mission aimed at sample return from Phobos, stereo observations at the requested local time are crucial for creating a local shape model of landing site candidates. To optimize the observation scheduling and facilitate as many stereo observations as possible within a limited time, we address the Phobos observation scheduling optimization problem and customize a genetic algorithm previously proposed for Earth observation satellites. Our ingenuity integrates elements related to stereo observations and local time constraints such that they can be applied to observation scheduling for planetary exploration. The scheduling demonstration results illustrate that 38 of the 50 landing site candidates can be observed during stereo viewing. Furthermore, we perform a sensitivity analysis of the number of landing site candidates to be scheduled, which will provide insights for improving the MMX operational planning.

Millimeter-sized silicate spherules embedded in primitive meteorites, namely, “chondrules,” are the primary solid component of the early solar nebula. They exhibit distinctive solidification textures, formed through rapid cooling from a molten state. The formation conditions of these textures have primarily been inferred on the basis of dynamic crystallization experiments; however, the theoretical verification of the solidification process has been largely neglected. Here, we conducted numerical simulations of the solidification of chondrule melt and successfully reproduced a crystal growth pattern resembling a typical barred olivine chondrule texture. This pattern emerged under conditions of rapid cooling, exceeding 10 4 kelvins hour −1 , which is substantially larger than those inferred experimentally. These results suggest that theories of chondrule formation in the nebula, which have been developed based on experimental results, should be reexamined.

The successful sample return from asteroid (162173) Ryugu by Hayabusa2 has contributed to our understanding of the solar system evolution. Over the course of the initial sample analysis, various measurements were conducted, such as mineralogical observation, chemical analysis, and mechanical property measurement. These pieces of information allow us to give constraints on the essential conditions of Ryugu's formation and evolution processes (e.g., thermal environment, aqueous alteration, formation of a rubble-pile body), leading to a clearer view of the early solar system. Here, we report the initial results of the elastic properties of Ryugu particles (e.g., P- and S-wave velocities and Young's modulus) obtained via ultrasonic pulse transmission measurement. Our measurement results showed 2.15 +/- 0.05 km/s and 1.25 +/- 0.05 km/s for the compressional and shear waves, respectively. Regarding Young's modulus, we obtained 7.1 +/- 0.6 GPa, consistent with the previously measured value via a nanoindentation test. Compared with the elastic properties of other carbonaceous chondrites (Tagish Lake, Tarda, Ivuna, and Murchison meteorites), we found that Ryugu had distinctly lower rigidity than Ivuna-the most similar material to Ryugu with respect to chemical and mineralogical features. Instead, Tagish Lake showed the closest elastic properties to Ryugu samples. The affinities in chemical and mineralogical features indicate the genetic relationship between Ryugu and Ivuna. On the other hand, the difference in elastic properties might indicate their formation and evolution processes proceeded differently (e.g., formation depth, degree of alteration).

Rubinite (IMA 2016-110) is a recently discovered Ti3+-dominant refractory mineral in the garnet group from the solar nebula. It has the Ia (3) over bard garnet-type structure with a = 12.19(1) angstrom, Z = 8, and an end-member formula of Ca3Ti23+Si3O12. Rubinite was identified as micrometer-sized crystals in five refractory Ca,Al-rich inclusions (CAIs) from the CV3 carbonaceous chondrites Allende, Efremovka, and Vigarano. In the Vigarano CAI V3, it occurs in the central portion of an ultra-refractory fragment with Zr,Y,Sc-oxide, spinel, and davisite-diopside, all enclosed within an amoeboid olivine aggregate. In the Allende Compact Type A (CTA) CAI AE01-01, it occurs with gehlenitic melilite, perovskite, spinel, hibonite, davisite, grossmanite, and diopside. In Efremovka, rubinite occurs within gehlenitic melilite with perovskite, spinel, and grossmanite in three CTA CAIs E101, E105, and 40E-1 (in a compound CAI). Rubinite is present in spinel-poor regions in all four of the Efremovka and Allende CAIs, but it is in contact with spinel in the Vigarano inclusion. The mean chemical composition of type rubinite in Allende is (in wt%) CaO 32.68, Ti2O3 14.79, TiO2 13.06, SiO2 28.37 Al2O3 3.82, Sc2O3 1.80, Na2O 1.01, ZrO2, 0.80, MgO 0.79, V2O3 0.61, FeO 0.53, Y2O3 0.07, Cr2O3 0.05, total 98.38, giving rise to an empirical formula of (Ca2.94Na0.08)(Ti(1.04)(3+)Ti(0.59)(4+)Sc(0.13)Mg(0.10)V(0.04)Fe0.04Zr0.03)(Si2.38Al0.38Ti0.244+)O-12, where Ti3+ and Ti4+ are partitioned based on stoichiometry. Efremovka rubinite has a similar composition with a mean empirical formula of (Ca2.97Na0.06)(Ti1.053+Ti0.664+Mg0.12Sc0.09Zr0.03V0.03Y0.01Fe0.01)(Si2.36Al0.48Ti0.164+)O-12. Vigarano rubinite is much more Y-, Sc-, and Zr-rich, having an empirical formula of (Ca1.89Y0.83Mg0.28)(Ti0.593+Sc0.50Zr0.72Mg0.2V0.02Cr0.01)(Si1.64Al1.18Ti0.074+Fe0.06)O-12. All rubinites are Ti3+-rich, but a significant amount (11-46%) of the Ti is 4+. In the Efremovka CTAs, spinel is O-16-rich (Delta O-17 similar to -24 parts per thousand); rubinite and perovskite show limited ranges of Delta O-17 (from -24 to -16 parts per thousand; most analyses range from -24 to -20 parts per thousand); melilite and grossmanite are the most O-16-depleted minerals (Delta O-17 range from similar to -10 to -4 parts per thousand and from -8 to -5 parts per thousand, respectively). In the Allende CTA AE01-01, spinel and hibonite are O-16-rich (Delta O-17 similar to -24 parts per thousand); melilite, rubinite, and perovskite show large ranges in Delta O-17 (from -23 to -3 parts per thousand, from -21 to -6 parts per thousand, and from -14 to -2 parts per thousand, respectively); grossmanite is uniformly O-16-depleted (Delta O-17 similar to-3 parts per thousand). Rubinite formed under highly reducing conditions in the solar nebula by gas-solid condensation and crystallization from a Ca-, Al-, and Ti-rich melt. Subsequently, most rubinite grains in the Allende CAI and some in the Efremovka CAIs may have experienced O-isotope exchange to various degrees with an O-16-depleted (Delta O-17 similar to -2 parts per thousand) aqueous fluid on the CV chondrite parent asteroid. However, crystallization from a Ca,Al,Ti-rich melt that recorded O-isotope exchange with nebular gas with variable Delta O-17 or post-crystallization O-isotope with such gas cannot be excluded. The mineral name is in honor of Alan E. Rubin (b. 1953), a cosmochemist at the University of California, Los Angeles (UCLA), U.S.A., for his many contributions to research in cosmochemistry and mineralogy of meteorites.

Nucleosynthetic isotope variations are powerful tracers to determine genetic relationships between meteorites and planetary bodies. They can help to link material collected by space missions to known meteorite groups. The Hayabusa 2 mission returned samples from the Cb-type asteroid (162173) Ryugu. The mineralogical, chemical, and isotopic characteristics of these samples show strong similarities to carbonaceous chondrites and in particular CI chondrites. The nucleosynthetic isotope compositions of Ryugu overlap with CI chondrites for several elements (e.g., Cr, Ti, Fe, and Zn). In contrast to these isotopes, which are of predominately supernovae origin, s -process variations in Mo isotope data are similar to those of carbonaceous chondrites, but even more s- process depleted. To further constrain the origin of this depletion and test whether this signature is also present for other s -process elements, we report Zr isotope compositions for three bulk Ryugu samples (A0106, A0106-A0107, C0108) collected from the Hayabusa 2 mission. The data are complemented with that of terrestrial rock reference materials, eucrites, and carbonaceous chondrites. The Ryugu samples are characterized by distinct 96 Zr enrichment relative to Earth, indicative of a s -process depletion. Such depletion is also observed for carbonaceous chondrites and eucrites, in line with previous Zr isotope work, but it is more extreme in Ryugu, as observed for Mo isotopes. Since s -process Zr and Mo are coupled in mainstream SiC grains, these distinct s- process variations might be due to SiC grain depletion in the analyzed materials, potentially caused by incomplete sample digestion, because the Ryugu samples were dissolved on a hotplate only to avoid high blank levels for other elements (e.g., Cr). However, local depletion of SiC grains cannot be excluded. An alternative, equally possible scenario is that aqueous alteration redistributed anomalous, s -process-depleted, Zr on a local scale, for example, into Ca-phosphates or phyllosilicates.

It is now possible to bring back samples from planetary bodies of the Solar System other than the moon. This research method enables a direct link between astronomical observations and meteorite analyses, which were previously disconnected. The Hayabusa, Hayabusa2, and OSIRIS REx sample return missions have provided detailed information on the composition of S-, C-, and B-type asteroids, respectively, and the processes by which they were formed. This paper reviews the results of these three asteroid sample return missions, and also introduces the next Martian moon sample return mission MMX. Although sample returns are currently achieved only from near-Earth objects in the Solar System, it is hoped that in the future it will be possible to collect samples from outer Solar System objects and even from small objects flying from outside the Solar System.

MIRS (MMX InfraRed Spectrometer) is a push-broom imaging spectrometer onboard of the JAXA sample return MMX mission. It has been built by the French laboratory LESIA, today LIRA (Laboratory for Instrumentation and Research in Astrophysics) of Paris Observatory-PSL in collaboration with five other French laboratories, collaboration and financial support of CNES and close collaboration with JAXA and MELCO. MIRS, designed to accomplish the MMX scientific objectives, has been built to be adapted on MMX Exploration Module. MIRS will remotely observe the Martian system for three years. MIRS will observe Phobos, Deimos and Mars in the spectral range 0.9–3.6 µm to characterize surface composition of the satellites and investigate Martian atmospheric variations. An overview of the MIRS Flight Model is presented as well as the data processing and the expected results.

Surface porosity and texture has been found to be an important property for small bodies. Some asteroids and comets can exhibit an extremely high surface porosity in the first millimeter layer. This layer may be produced by various processes and maintained by the lack of an atmosphere. However, the influence of porosity on the spectro-photometric properties of small body surfaces is not yet fully understood. In this study, we looked into the effect of the texture on the spectro-photometric properties of Phobos regolith spectroscopic simulants. Macro-and micro-porosity were created by mixing the simulants with ultra-pure water, producing ice-dust particles, and then sublimating the water. The sublimation of the water ice enabled the production of porous and rough powdered simulants with significant micro-and macro-porosity associated with macro-roughness. The reflectance spectroscopic properties in the visible and near-infrared (0.5-4.2 mu m) demonstrate a brightening of the porous samples in comparison to the compact ones. One simulant exhibits a bluing of the spectral slope after increasing porosity, which is likely linked to the presence of expandable phyllosilicates. In the mid-infrared range, a contrast increase of the 10 mu m emissivity-related plateau due to silicates is observed. This spectral feature is typically observed as a 10 mu m emissivity plateau on some asteroids, making the mid-infrared region important for assessing mineralogy and surface texture. Photometry reveals a modification of the phase reddening behavior between the compact powder and the sublimation residue for both simulants. However, the observed behavior is different between the simulants, suggesting that the phase reddening may be dependent on the composition of the simulants. The phase curves of the sublimation residues exhibit a higher contribution of forward scattering. The derivation of the Hapke parameters indicates an increase in roughness for the porous sample, but no significant modification of the opposition effect. The modifications of the spectrophotometric properties observed in this experiment are definitely due to the textural changes obtained after sublimation, which depend on the initial composition of the simulants. This study aims to provide new insights into the understanding of porosity by using two Phobos simulants in the context of the upcoming JAXA/Martian Moons eXploration mission. We suggest that the Phobos blue unit may be due to the presence of a highly porous layer, rather than only to space-weathering processes, as often postulated.

Carbonaceous asteroids are the source of the most primitive meteorites1 and represent leftover planetesimals that formed from ice and dust in the outer Solar System and may have delivered volatiles to the terrestrial planets2-5. Understanding the aqueous activity of asteroids is key to deciphering their thermal, chemical and orbital evolution, with implications for the origin of water on the terrestrial planets. Analyses of the objects, in particular pristine samples returned from asteroid Ryugu, have provided detailed information on fluid-rock interactions within a few million years after parent-body formation6-11. However, the long-term fate of asteroidal water remains poorly understood. Here we present evidence for fluid flow in a carbonaceous asteroid more than 1 billion years after formation, based on the 176Lu-176Hf decay systematics of Ryugu samples, which reflect late lutetium mobilization. Such late fluid flow was probably triggered by an impact that generated heat for ice melting and opened rock fractures for fluid migration. This contrasts the early aqueous activity powered by short-lived radioactive decay, with limited fluid flow and little elemental fractionation12. Our results imply that carbonaceous planetesimals accreted by the terrestrial planets could have retained not only hydrous minerals but also aqueous water, leading to an upwards revision of the inventory of their water delivery by a factor of two to three.

Asteroid Itokawa is made of reassembled fragments from a monolithic parent asteroid which got shattered during a collision with a large object. Data are scarce regarding the metamorphic processes that occurred on the monolithic parent body and the age and nature of the catastrophic disruption event. Here, we investigate the timing of the metamorphism inside the parent body of Asteroid Itokawa and the age and nature of the catastrophic breakup event recorded in particles returned from Itokawa. We studied three regolith dust particles recovered by the Hayabusa space craft from the rubble pile asteroid 25143 Itokawa using electron backscatter diffraction, time-of-flight secondary ion mass spectrometry, and Ar-40/Ar-39 dating techniques. Our results show that none of the particles show noticeable sign of shock metamorphism. Two of the particles yielded Ar-40/Ar-39 age of 4559 +/- 61 and 4130 +/- 33 million years (Ma), while a third particle returned a maximum error age of 703 +/- 53 Ma. When combined with existing data, and diffusion models, these results show that similar to 4.5 billion years (Ga) ago, Itokawa's parent monolithic body cooled down from a peak metamorphism temperature similar to 800 degrees C to similar to 300 degrees C in less than 64 million years at a depth of >20 km. Then at similar to 4.22 Ga, Itokawa's parent body was shattered in a collisional process involving a heterogeneous temperature distribution during the impact, with some regions escaping shock metamorphism and experiencing less than a few hundred degrees Celsius. The fragments re-agglomerated in a larger rubble pile body where they subsequently cooled down over tens of millions of years. For the next 4 billion years, Asteroid Itokawa was regularly impacted and progressively shrunk by mass wasting.