Typical Asteroid Research Articles

Iron rich basaltic eucrites, implication on spectral properties and parental bodies

The Howardites-Eucrite-Diogenite achondrite family is recognized to be the set of extraterrestrial rocks coming from (4) Vesta and Vestoids. In fact, the similar values of oxygen isotopes, and some chemical variation permit to associate these rocks to a system genetically correlated. Reflectance spectral properties permit an association between these achondrites and the (4) Vesta and Vestoids crust. Despite this closer connection, some Eucrites show spectral properties comparable with their pyroxene composition but strongly shifted, in terms of spectral parameters, with respect to the values retrieved for their parental bodies. The results from this work show how these eucrites have an evident shift of the main absorptions without peculiar geochemical variation within the family with respect to the data of the supposed parental body.Here, we evidence how these eucrites show an iron enriched pigeonite indicating these samples underwent a very quick cooling which could be associated to erupting material onto the surface of its parental body. Their distribution on the surface could be then limited to small areas that could be detected only at high spatial resolution on (4) Vesta or Vestoids. Nevertheless, the relationship among band center I and the band area ratio show how these samples could also fit with parental bodies shifted from the typical basaltic achondrites regions and moving closer to the characteristics of other pyroxenes enriched material like SIII-SV type Asteroids.

Photometric observations of the potentially hazardous asteroid (99942) Apophis from Kawabe Cosmic Park

Abstract 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.

The proposed Silicate-Sulfuric Acid Process: Mineral processing for In Situ Resource Utilization (ISRU)

Volatile elements and compounds found in extra-terrestrial environments are often the target of In Situ Resource Utilization (ISRU) studies. Although water and hydroxide are most commonly the focus of these studies as they can be used for propellant and human consumption; we instead focus on the possible exploitation of sulfur and how it could be utilized to produce building materials on the Moon, Mars and Asteroids. We describe the physical and chemical pathways for extracting sulfur from native sulfide minerals, manufacturing sulfuric acid in situ, and using the produced acid to dissolve native silicate minerals. The final products of this process, which we call the Silicate-Sulfuric Acid Process (SSAP), include iron metal, silica, oxygen and metal oxides, all of which are crucial in the scope of a sustainable, space-based economy. Although our proposed methodology requires an initial investment of water, oxygen, and carbon dioxide, we show that all of these volatiles are recovered and reused in order to repeat the process. We calculate the product yield from this process if it were enacted on the lunar highlands, lunar mare, Mars, as well as an array of asteroid types.

The Moon at thermal infrared wavelengths: a benchmark for asteroid thermal models

Thermal-infrared measurements of asteroids, satellites, and distant minor bodies are crucial for deriving the objects’ sizes, albedos, and in some cases, also the thermophysical properties of the surface material. Depending on the available measurements and auxiliary data, such as visual light curves, spin and shape information, or direct size measurements from occultations or high-resolution imaging techniques, a range of simple to complex thermal models are applied to achieve specific science goals. However, testing these models is often a difficult process and the uncertainties of the derived parameters are not easy to estimate. Here, we make an attempt to verify a widely accepted thermophysical model (TPM) against unique thermal infrared (IR), full-disk, and well-calibrated measurements of the Moon. The data were obtained by the High-resolution InfraRed Sounder (HIRS) instruments on board a fleet of Earth weather satellites that serendipitously scan the surface of the Moon. We found 22 Moon intrusions, taken in 19 channels between 3.75 μm and 15.0 μm, and over a wide phase angle range from −73.1° (waxing Moon) to +73.8° (waning Moon). These measurements include the entire Moon in a single pixel, seen almost simultaneously in all bands. The HIRS filters are narrow and outside the wavelength regime of the Christiansen feature. The similarity between these Moon data and typical asteroid spectral-IR energy distributions allows us to benchmark the TPM concepts and to point out problematic aspects. The TPM predictions match the HIRS measurements within 5% (10% at the shortest wavelengths below 5 μm) when using the Moon’s known properties (size, shape, spin, albedo, thermal inertia, roughness) in combination with a newly established wavelength-dependent hemispherical emissivity. In the 5–7.5 μm and in the 9.5–11 μm ranges, the global emissivity model deviates considerably from the known lunar sample spectra. Our findings will influence radiometric studies of near-Earth and main-belt asteroids in cases where only short-wavelength data (from e.g., NEOWISE, the warm Spitzer mission, or ground-basedM-band measurements) are available. The new, full-disk IR Moon model will also be used for the calibration of IR instrumentation on interplanetary missions (e.g., for Hayabusa-2) and weather satellites.

Symmetric Periodic Orbits in the Dipole-segment Problem for Two Equal Masses

Abstract We consider a relatively simple model to represent some types of asteroids that are very elongated and with two protuberances on their end points. A conspicuous example of this type of body is asteroid 216-Kleopatra. To model such bodies, we consider a dipole segment, which consists of a massive segment with two spherical masses at the end point of the rod and which is rotating about its center of mass with uniform velocity. In particular, we restrict our study to the case in which both massive spheres are equal. For this problem, we obtain the potential, equilibria, and stability and compute the families of symmetric periodic orbits. We also discover asymptotic points in the family map, which represents heteroclinic orbits connecting different equilibria.

Design and Experimental Research of a New Type of Asteroid Anchoring System

Asteroid detection is of great significance to the study of the formation of the solar system and the origin of life. However, there are many types of asteroids, and they are far away from the earth, and the understanding of their various characteristics is not clear, which brings huge technical challenges to the landing and attachment of star catalogs. At present, the world is mainly based on surround, overflight, and short-term contact detection, and long-term attachment detection has not yet been realized. In order to solve the long-term attachment detection requirements of asteroids, focusing on the geological characteristics of various types of stars, this paper proposes a new type of asteroid attachment mechanism based on the beetle bionic theory, which can realize intelligent and flexible attachment and has strong adaptability. Around this design, this paper analyzes the mechanism of adhesion and realizes the adaptive matching of unascertained terrain landing point adhesion. On this basis, a prototype of the asteroid landing attachment mechanism was developed and verified by experiments. The experiment proved that the mechanism has strong multiterrain matching ability and can obtain an adhesion force of not less than 36 N on ordinary concrete ground.

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.

Ejecta distribution from impact craters on Ryugu: Possible origin of the bluer units

Asteroid (162173) Ryugu was the first spinning-top-shaped asteroid to be closely approached by a probe, the Hayabusa2 spacecraft, which sent numerous high-resolution images of Ryugu to the Earth and revealed the nature of this type of asteroid. One of the notable features of Ryugu is the equatorial ridge, which is considered the result of rapid spin in the past. Despite the advanced age of the ridge, indicated by the presence of numerous craters, the ridge exhibits a bluish color, indicating that it is covered with fresh material. In addition to Ryugu, many other asteroids have similar blue areas, which are considered the result of ejecta emplacement. We examined the distribution of ejecta blankets from actual craters on Ryugu to assess ejecta emplacement as a possible origin of Ryugu's bluer units. We determined that when Ryugu's rotation was fast, ejecta from craters formed at lower latitudes accumulated along the equator, which may explain the bluish color of the equatorial ridge. On the other hand, ejecta emplacement does not fully explain the bluish color of Tokoyo Fossa, although we attempted to find the corresponding ejecta blankets.

Visible-infrared spectroscopy of ungrouped and rare meteorites brings further constraints on meteorite-asteroid connections

The composition of asteroids gives crucial insights into the formation and evolution of the Solar System. Although spectral surveys and spacecraft missions provide information on small bodies, many important analyses can only be performed in terrestrial laboratories. Meteorites represent our main source of samples of extraterrestrial material. Determining the source asteroids of these meteorites is crucial to interpret their analyses in the broader context of the inner Solar System. For now, the total number of parent bodies represented in our meteorites collection is estimated to about 150 parent bodies, of which 50 parent bodies represented by the poorly studied ungrouped chondrites. Linking ungrouped meteorites to their parent bodies is thus crucial to significantly increase our knowledge of asteroids. To this end, the petrography of 25 ungrouped chondrites and rare meteorite groups was studied, allowing grouping into 6 petrographic groups based on texture, mineralogy, and aqueous and thermal parent body processing. Then, we acquired visible-near-infrared (VIS-NIR) reflectance spectroscopy data of those 25 meteorites, in order to compare them to ground-based telescopic observations of asteroids. The reflectance spectra of meteorites were obtained on powdered samples, as usually done for such studies, but also on raw samples and polished sections. With asteroids surfaces being more complex than fine-grained regolith (e.g., asteroid (101955) Bennu), in particular near-Earth asteroids, the use of raw samples is a necessary addition for investigating parent bodies. Our results showed that sample preparation influences the shape of the spectra, and thus asteroid spectral matching, especially for carbonaceous chondrites. Overall, the petrographic groups defined initially coincide with reflectance spectral groups, with only few exceptions. The meteorite spectra were then compared with reference end-member spectra of asteroids taxonomy. We matched the 25 studied meteorites to asteroids types, using a qualitative match of the shape of the spectra, as well as a quantitative comparison of spectral parameters (bands positions, bands depths and slopes at 1 and 2 μm). We define links between some of the studied ungrouped chondrites and asteroid types that had no meteorite connection proposed before, such as some very primitive type 3.00 ungrouped chondrites to B-type or Cg-type asteroids. We also matched metamorphosed ungrouped carbonaceous chondrites to S-complex asteroids, suggesting that this complex is not only composed of ordinary chondrites or primitive achondrites, as previously established, but may also host carbonaceous chondrites. Conversely, some ungrouped chondrites could not be matched to any known asteroid type, showing that those are potential samples from yet unidentified asteroid types.

The nature of bright C-complex asteroids

ABSTRACT Most C-complex asteroids have albedo values less than 0.1, but there are some high-albedo (bright) C-complex asteroids with albedo values exceeding 0.1. To reveal the nature and origin of bright C-complex asteroids, we conducted spectroscopic observations of the asteroids at visible and near-infrared wavelengths. As a result, the bright B-, C-, and Ch-type (Bus) asteroids, which are subclasses of the Bus C-complex, are classified as DeMeo C-type asteroids with concave curvature, B-, Xn-, and K-type asteroids. Analogue meteorites and material (CV/CK chondrites, enstatite chondrites/achondrites, and salts) associated with these spectral types of asteroids are thought to be composed of minerals and material exposed to high temperatures. A comparison of the results obtained in this study with the SDSS photometric data suggests that salts may have occurred in the parent bodies of 24 Themis and 10 Hygiea, as well as 2 Pallas. The bright C-complex asteroids in other C-complex families were likely caused by impact heating. Bright C-complex asteroids that do not belong to any families are likely to be impact-metamorphosed carbonaceous chondrites, CV/CK chondrites, or enstatite chondrites/achondrites.

Novel 3U Stand-Alone CubeSat Architecture for Autonomous Near Earth Asteroid Fly-By

The purpose of this work is to present a novel CubeSat architecture, aimed to explore Near Earth Asteroids. The fast growth in small satellite commercial-off-the-shelf technologies, which characterized the last decade of space industry, is exploited to design a 3U CubeSat able to provide a basic scientific return sufficient to improve the target asteroid dataset. An overview of the current available technologies for each subsystem is presented, followed by a component selection driven by the mission constraints. First a typical asteroid fly-by mission is introduced together with the system and performance requirements. Then each characterizing subsystem is critically analyzed, and the proposed configuration is presented, showing the mission feasibility within only 3.9 kg of wet mass and 385 m/s of total ΔV.

The Oxygen Isotope Compositions of Large Numbers of Small Cosmic Spherules: Implications for Their Sources and the Isotopic Composition of the Upper Atmosphere

AbstractCosmic spherules are micrometeorites that melt at high altitude as they enter Earth's atmosphere, and their oxygen isotope compositions are partially or completely inherited from the upper atmosphere, depending on the amount of heating experienced and the nature of their precursor materials. In this study, the three oxygen isotope compositions of 137 cosmic spherules are determined using 277 in situ analyses by ion probe. Our results indicate a possible correlation between increasing average δ18O compositions of silicate‐dominated (S‐type) spherules along the series scoriaceous < porphyritic < barred < cryptocrystalline < glass < CAT (calcium‐aluminum‐titanium) spherules (~12‰, 20‰, 22‰, 25‰, 26‰, and 50‰). This is consistent with the evolution of oxygen isotopes by mass fractionation owing to increased average entry heating and thus suggests mass fractionation dominates changes in isotopic composition, with atmospheric exchange being less significant. The Δ17O values of spherules, therefore, are mostly preserved and suggest that ~80% of particles are samples of C‐type asteroids. The genetic relationships between different S‐types can also be determined with scoriaceous, barred, and cryptocrystalline spherules mostly having low Δ17O values (≤0‰) mainly derived from carbonaceous chondrite (CC)‐like sources, while porphyritic spherules mostly have positive Δ17O (>0‰) and are largely derived from ordinary chondrite (OC)‐like sources related to S (IV)‐type asteroids. Glass and CAT spherules have variable Δ17O values indicating they formed by intense entry heating of both CC and OC‐like materials. I‐type cosmic spherules have a narrow range of δ17O (~20–25‰) and δ18O (~38–48‰) values, with Δ17O (~0‰) suggesting their oxygen is obtained entirely from the Earth's atmosphere, albeit with significant mass fractionation owing to evaporative heating. Finally, G‐type cosmic spherules have unexpected isotopic compositions and demonstrate little mass fractionation from a CC‐like source. The results of this study provide a vital assessment of the wider population of extraterrestrial dust arriving on Earth.

A Deep Search for Stable Venus Co-orbital Asteroids: Limits on the Population

Abstract A stable population of objects co-orbiting with Venus was recently hypothesized in order to explain the existence of Venus’s co-orbital dust ring. We conducted a five days twilight survey for these objects with the Cerro-Tololo Inter-American Observatory 4 m telescope covering about 35 unique square degrees to 21 mag in the r band. Our survey provides the most stringent limit so far on the number of Venus co-orbital asteroids; it was capable of detecting 5% of the entire population of those asteroids brighter than 21 mag. We estimate an upper limit on the number of co-orbital asteroids brighter than 21 mag (approximately 400–900 m in diameter depending on the asteroid albedo) to be . Previous studies estimated the mass of the observed dust ring co-orbiting with Venus to be equivalent to an asteroid with a 2 km diameter ground to dust. Our survey estimates <6 asteroids larger than 2 km. This implies the following possibilities: that Venus co-orbitals are nonreflective at the observed phase angles, have a very low albedo (<1%), or that the Venus co-orbital dust ring has a source other than asteroids co-orbiting Venus. We discuss this result, and as an aid to future searches, we provide predictions for the spatial, visual magnitude, and number density distributions of stable Venus co-orbitals based on the dynamics of the region and magnitude estimates for various asteroid types.

Model for asteroid regolith to guide simulant development

When creating asteroid regolith simulant, it is necessary to have a model of asteroid regolith to guide and to evaluate the simulant. We created a model through evaluation and synthesis of the available data sets including (1) the returned sample from Itokawa by the Hayabusa spacecraft, (2) imagery from the Hayabusa and NEAR spacecraft visiting Itokawa and Eros, respectively, (3) thermal infrared observations from asteroids, (4) the texture of meteorite regolith breccias, and (5) observations and modeling of the ejecta clouds from disrupted asteroids. Comparison of the Hayabusa returned sample with other data sets suggest the surficial material in the smooth regions of asteroids is dissimilar to the bulk regolith, probably due to removal of fines by photoionization and solar wind interaction or by preferential migration of mid-sized particles into the smooth terrain. We found deep challenges interpreting and applying the thermal infrared data so we were unable to use those observations in the model. Texture of regolith breccias do not agree with other data sets, suggesting the source regolith on Vesta was coarser than typical asteroid regolith. The observations of disrupted asteroids present a coherent picture of asteroid bulk regolith in collisional equilibrium, unlike lunar regolith, HED textures, and the Itokawa returned sample. The model we adopt consists of power laws for the bulk regolith in unspecified terrain (differential power index −3.5, representing equilibrium), and the surficial regolith in smooth terrain (differential power index −2.5, representing disequilibrium). Available data do not provide adequate constraints on maximum and minimum particle sizes for these power laws, so the model treats them as user-selectable parameters for the simulant.

Concepts of the Small Body Sample Return Missions - the 1st 10 Million Year Evolution of the Solar System

Each type of asteroids and comets are important, serving as the unique puzzle pieces of the solar system. The countless number of small bodies spread vastly from the near-Earth orbits to the main belt and beyond Jupiter. Thus, in order to complete the whole puzzle, and hence requires a well-designed roadmap of sample return (SR) missions and international coordination. The main consideration is the accreting locations of various types of asteroids, which may be referred through their redox status and abundances of water and volatile components. C-complex asteroids are water and volatile-rich, likely accreted in the outer solar system. Two C-complex asteroids are being explored by Hayabusa-2 and OSIRIS-REx missions, respectively. In contrast, enstatite chondrite-like asteroids formed under extremely reducing conditions in the inner solar system. The samples returned from enstatite chondrite-like asteroids will clarify the nebular processes in the zone closest to the Sun, and reveal fractionation of the solar nebula along the radial direction, via comparing with those of the C-complex asteroids. The exploration will also shed light on the bulk compositions of the Earth and terrestrial planets accreted in the same region of the inner solar system. The SR missions will focus on the first 10 Ma history of the solar system, including the initial condition, the nebular processes, and the accretion of planetesimals. Because the secondary processes that took place in planetesimals, such as thermal metamorphism, aqueous alteration, melting and differentiation, could largely erase the records of the nebular events, it is critically important to choose the primordial asteroid targets. Although C-complex asteroids accreted at low temperature in the outer solar nebula, they, especially those hydrated, could have suffered severe aqueous alteration as observed in CM chondrites. Other preferred targets are L-type asteroids, which probably contain abundant Ca-, Al-rich inclusions, the first solid assemblages of the solar system. Based on the roadmap of SR missions, we propose to return samples first from enstatite chondrite-like or L-type Near-Earth asteroids.

Exploration: Safe and clean mining on Earth and asteroids

The shallow mineral resources tend to run out in the near future. Meanwhile, numerous catastrophic safety accidents have been induced and serious environmental damage has been caused due to the long-term predatory mining. In this paper, we explored the safe and clean mining on Earth and asteroids by integrating safety and cleanliness into the whole process of mining production. As for the safe and clean mining on Earth, we elaborated the root causes and major influencing factors for the safety accidents occurred frequently and presented specific measures to optimize the entire mining production in the aspects of open-pit mining and underground mining. On the other hand, the possible mining methods and facilities on asteroids were proposed through the overall consideration of safety and cleanliness, which mainly include the asteroid capturing method, open cutting method, and underground filling method. Furthermore, the adaptations of these off-Earth mining methods to different types of asteroids, as well as their own advantages and disadvantages were discussed and clarified. Additionally, some helpful suggestions were discussed to prevent and control the current disasters caused by traditional mining methods. The exploration of safe and clean mining on Earth and asteroids can not only provide guidance for the current and future extraction of valuable mineral resources, but also a benefit for the sustainable development of green mining and environment.

Mineralogical Criteria for the Parent Asteroid of the “Carbonaceous” Achondrite NWA 6704

Abstract The unique achondrite meteorite Northwest Africa (NWA) 6704 and its paired samples are fragments of an unknown parent asteroid that experienced large-scale igneous melting early in our solar system’s history. The geochemistry and mineralogy of NWA 6704 show that its parent asteroid has affinities with carbonaceous chondrites and that the precursor materials were relatively oxidized. While large-scale melting has affected the meteorite, there is no evidence for equilibration with a metallic melt. NWA 6704 paired meteorites therefore provide insights into the evolution of planetesimals and bodies that accreted from source materials, possibly in the ice-rich outer solar system. Currently, we lack an understanding of the distribution of potential parent asteroids of the NWA 6704 meteorites. We have undertaken a detailed multiwavelength (0.35–25 μm) spectroscopic and geochemical investigation of NWA 6704 to provide constraints on the potential parent asteroids of these enigmatic meteorites. In comparison with asteroid spectra, NWA 6704 is similar to the S(VI) subtypes of the S-asteroid complex. By using the Bus-DeMeo Taxonomic Classifier, we determine that NWA 6704 has affinities toward V-type (Vesta type) asteroids. We have determined that the parent asteroid of NWA 6704 would be a V-type asteroid that is not dynamically linked to Vesta and also fall in the S(VI) subtype of the Band I center versus Band area ratio diagram. A search in the literature for potential parent bodies yielded one asteroid, (34698) 2001 OD22, as a possible candidate.

Primordial organic matter in the xenolithic clast in the Zag H chondrite: Possible relation to D/P asteroids

Some xenolithic clasts in meteorites may have originated from unique primitive Solar System bodies. These clasts would provide novel insights into the early evolution of the Solar System. We conducted multiple analyses of organic matter (OM) in a CI-like xenolithic clast in the Zag (H5) meteorite including bulk elemental and isotopic analysis, FTIR, STXM/XANES, and NanoSIMS. The bulk C and N abundances in the Zag clast were +5.1 ± 0.4 wt.% and +0.26 ± 0.01 wt.%, respectively, which were the highest observed among various chondrite groups. The bulk δ13C value of the Zag clast was +23.0 ± 4.1‰ which was close to the value of the Tagish Lake meteorite; the δ15N value was +300 ± 3‰ which was close to the values of CR chondrites and Bells (a unique CM). The δD values of C-rich regions obtained by NanoSIMS were approximately +600 to +2000‰ which were close to the values of IOM from CI, CM and Tagish Lake. Some isotopic “hot spots” were observed with δD values up to ≈ +4000‰ and δ15N values up to ≈ +5500‰. The infrared transmission spectrum of the Zag clast was consistent with the abundant phyllosilicates and carbonates observed in the clast. The STXM showed abundant OM in various forms. C-XANES spectra from the OM were generally similar to CI/CM/CR chondrites. However, some variations existed in the molecular structures. OM in the Zag clast was partially associated with carbonates. The functional group, elemental and isotopic signatures of the OM in the Zag clast support the idea that the Zag clast is unique among known carbonaceous chondrite groups and originated from the outer Solar System such as aqueously-altered D/P type asteroids.

Dependence of Light Curves on Phase Angle and Asteroid Shape

Abstract We investigate the phase angle dependence of asteroid light curves using numerical scattering models applied to simple body shapes. For simplicity, the Kaasalainen scattering parameters are obtained from the corresponding Hapke scattering laws for C-type, S-type, and V-type asteroids. The spectral types differ substantially in the role of multiple scattering (which is largely a function of their geometric albedos) but we find that the differences on the light curve versus phase relations are modest. Using a Kaasalainen scattering law, the amplitudes and axis ratios with respect to different phase angles from 0° to 140° are plotted for these types of asteroids based on a biaxial ellipsoid shape model. Additionally, we examine the relationship between amplitude and the axis ratio for a contact binary represented by identical biaxial ellipsoids, including the effects of shadowing of one component by the other. We compare the models with published high phase angle observations, and with interstellar object 1I/‘Oumuamua (Δm = 2.5 mag at a phase angle of α = 23°), finding an axis ratio of 5.2: 1 if represented as a single ellipsoid and 3.5: 1 for each component if represented as a nose-to-nose contact binary. While a detailed fit is not attempted, the comparison shows that the single ellipsoid model is better.

Orbit-Attitude Coupled Tracking and Landing Control for an Asteroid

Recent research on asteroid exploration has shown tremendous potential to provide humankind detailed views of unexplored worlds in the inner solar system. A potential market of asteroid mining has aroused interest from commercial companies gradually. Asteroid exploration has the potential to offer the possibility to revolutionize the supply of many resources which are vital but exorbitant for human. A typical asteroid exploration mission is composed of remote asteroid detecting, approaching, hovering, landing and sampling, take-off and return, re-entry stage. Among these stages the tracking and landing control of the asteroid is crucial for the exploration. Rendezvous, approaching, fly-around and landing problem of an asteroid is investigated in this paper. The expected motion of the tracking spacecraft determined by the asteroid’ orbital and attitude status is presented firstly. According to the design of the OSIRIS-REx project, several constant thrusters are used for spacecraft to track the asteroid. Different control strategies like pulse control, saturated nonlinear control, limit cycle control and PWM based low-thrust control are developed to fulfil the asteroid’s tracking mission of different stages. Numerical simulations demonstrate the effectiveness of the tracking control.