Asteroid Surface Research Articles

On the optical properties and mineralogy of the surfaces of Near-Earth Asteroids

In this article, we review the literature for constraints on physical properties and mineral composition ofnear-Earth asteroids. We discuss spectroscopic and microscopic studies of optical and physical effectsand the surface structure of NEAs. This topic is of great importance to guess the nature and origin ofthese objects, and may help understanding investigation of extra-terrestrial bodies and providingindirect valuations of hazard on Earth via cosmic-ray bombardment, meteoroid, asteroid and cometimpacts.

Isolating the mechanisms for asteroid surface refreshing

Evidence is seen for young, fresh surfaces among Near-Earth and Main-Belt asteroids even though space-weathering timescales are shorter than the age of the surfaces. A number of mechanisms have been proposed to refresh asteroid surfaces on short timescales, such as planetary encounters, YORP spinup, thermal degradation, and collisions. Additionally, other factors such as grain size effects have been proposed to explain the existence of these “fresh-looking” spectra. To investigate the role each of these mechanisms may play, we collected a sample of visible and near-infrared spectra of 477 near-Earth and Mars Crosser asteroids with similar sizes and compositions — all with absolute magnitude H > 16 and within the S-complex and having olivine to pyroxene (ol/(ol+opx)) ratios >0.65. We taxonomically classify these objects in the Q (fresh) and S (weathered) classes. We find four trends in the Q/S ratio: (1) previous work demonstrated the Q/S ratio increases at smaller sizes down to H ≲16, but we find a sharp increase near H∼19 after which the ratio decreases monotonically. (2) in agreement with many previous studies, the Q/S ratio increases with decreasing perihelion distance, and we find it is non-zero for larger perihelia >1.2AU, (3) as a new finding our work reveals the Q/S ratio has a sharp, significant peak near ∼5° orbital inclination, and (4) we confirm previous findings that the Q/S ratio is higher for objects that have the possibility of encounter with Earth and Venus versus those that do not, however this finding cannot be distinguished from the perihelion trend. No single resurfacing mechanism can explain all of these trends, so multiple mechanisms are required. YORP spin-up scales with size, thermal degradation is dependent on perihelion, planetary encounters trend with inclination, perihelion and MOID, noting that asteroid–asteroid collisions are also dependent on inclination. It is likely that a combination of all four resurfacing mechanisms are needed to account for all observational trends.

Anticipated Geological Assessment of the (65803) Didymos–Dimorphos System, Target of the DART–LICIACube Mission

On 2022 September 26, the DART spacecraft will impact the surface of Dimorphos, the ∼160 m size satellite of the binary near-Earth asteroid (NEA) (65803) Didymos. What will be observed on the surfaces of both asteroids and at the DART impact site is largely unknown, beyond the details of Didymos revealed by previous Arecibo and Goldstone radar observations. We present here the expected DART and LICIACube observations of the Didymos system and discuss the planned mapping strategies. By searching similar geological features and processes identified on other NEAs, we constrain the impact conditions that DART might encounter at Dimorphos, assessing both the asteroid’s surface and interior structure.

Spectral Analysis of Ceres’ Main Linear Features

Linear features are very common on asteroid surfaces. They are generally formed after impact and provide information about asteroid evolution. This work focuses on a mineralogical and spectral analysis of the main linear features on the 1/Ceres surface, having both tectonic (Samhain Catena’s pit chains) and geomorphic origins, i.e., generated by ejecta material (Occator ejecta, Dantu’s secondary radial chains, secondary radial chains generated from the Urvara impact). The analysis is based on spectral parameters defined by the Dawn’s VIR imaging spectrometer data, as albedo and depths of the bands centered at approximately 2.7, 3.1, 3.4 and 3.9 mm. The geomorphic linear features show spectral variations with respect to the surroundings, i.e., ammoniated phyllosilicates band depth shallowing is caused by the presence of material originating in a different region or dehydration caused by impact. The Samhain Catena does not show any mineralogical variation, due to its tectonic origin. The spectral behavior of Ceres’ linear features is similar to that observed on other asteroids (Vesta, Eros) and can be diagnostic in discerning the origin of linear features. Then, we searched spectral signatures of organics in the Samhain Catena region, since they are expected to form at depth due to internal processes: the absence of such signatures indicates that either they form at a larger depth or that their subsurface distribution is uneven.

A record of post-accretion asteroid surface mixing preserved in the Aguas Zarcas meteorite

Particle ejection and redeposition events on the surface of asteroid 101955 Bennu, which led to transport, mixing and loss of material, have been observed frequently by NASA’s OSIRIS-REx mission. Besides large-scale impacts, this may be one of the most important post-accretional processes on small carbonaceous asteroids. Here we looked for relics of such activity in a Bennu analogue, the carbonaceous chondrite Aguas Zarcas. We discovered compact fragments that were strongly shocked, redistributed and deposited onto an unshocked lithology, consistent with surficial re-accretion on Aguas Zarcas’s parent body. Such re-accretion could be driven by large-scale impacts or by frequent pebble transport from endogenous asteroidal activity such as observed at Bennu. The latter hypothesis is supported by the matching size distribution of the Aguas Zarcas compact fragments with that of the Bennu ejecta. Such mixing has hitherto been unexplored in other regolith breccias, and further analysis will determine how common such processes are. Some fragments of the Aguas Zarcas carbonaceous meteorite have been shocked before being redeposited over an unshocked lithology. As their size distribution is similar to that of the ejecta observed at Bennu, they might be the signature of activity of the Aguas Zarcas parent body. Alternatively, they might be the result of a large-scale impact.

Effect of boulder size on ejecta velocity scaling law for cratering and its implication for formation of tiny asteroids

Ejecta velocity distribution is an important property for controlling asteroid surface evolution and for changing the size frequency distribution of asteroids and planetary dusts. Recent asteroid explorations revealed that boulders on an asteroid surface had a wide size frequency distribution. On the other hand, many studies on ejecta velocity distribution for cratering experiments used fine-grained homogeneous targets. Thus, to study the ejection process of various-sized boulders on rubble-pile asteroids, we conducted impact experiments using gas guns at impact velocities of 100 m s−1 to 4 km s−1 on targets with various-sized glass beads, and analyzed boulder trajectories in three dimensions to clarify the effect of grain size on ejection velocity distribution. The results showed that the ejection velocity, v0, decreased as the bead size increased, and the ejecta velocity scaling law was improved to v0gR=k2′r0+aR−1μ′ including the bead radius, a; r0 is the initial position of the bead, g is the gravitational acceleration, R is the crater radius, and k2′ and μ′ are, respectively, 0.58 ± 0.02 and 0.62 ± 0.02 for the low-impact velocity range (<200 m s−1) and 0.61 ± 0.07 and 0.57 ± 0.04 for the high-impact velocity range (>1 km s−1). Using our improved ejecta velocity scaling law, we calculated the landing points of ejected boulders and concluded that boulders with radii >0.34R could not be ejected outside the final crater. Moreover, when the Urashima crater on asteroid 162173 Ryugu was formed on the surface, boulders up to 64 m in diameter may have been ejected beyond the escape velocity of Ryugu to become tiny monolithic asteroids.

SHINeS: Space and High-Irradiance Near-Sun Simulator

We present SHINeS, a space simulator which can be used to replicate the thermal environment in the immediate neighborhood of the Sun down to a heliocentric distance r~0.06 au. The system consists of three main parts: the solar simulator which was designed and constructed in-house, a vacuum chamber, and the probing and recording equipment needed to monitor the experimental procedures. Our motivation for building this experimental system was to study the effect of intense solar radiation on the surfaces of asteroids when their perihelion distances become smaller than the semi-major axis of the orbit of Mercury. Comparisons between observational data and recent orbit and size-frequency models of the population of near-Earth asteroids suggest that asteroids are super-catastrophically destroyed when they approach the Sun. Whereas the current models are agnostic about the disruption mechanism, SHINeS was developed to study the mechanism or mechanisms responsible. The system can, however, be used for other applications that need to study the effects of high solar radiation on other natural or artificial objects.

Near-ultraviolet to visible spectroscopy of the Themis and Polana-Eulalia complex families

Context. Spectrophotometry data of asteroids obtained in the 1980s showed that there are large variations in their near-ultraviolet (NUV) reflectance spectra. Reflectance spectra at NUV wavelengths are important because they help detect the presence of hydrated minerals and organics on the asteroid surfaces. However, the NUV wavelength region has not been fully investigated yet using spectroscopic data. Aims. The aim of our study is to obtain the near-ultraviolet to visible (NUV-VIS, 0.35–0.95 μm) reflectance spectra of primitive asteroids with a focus on members of the Themis and Polana-Eulalia complex families. This characterization allows us to discuss the origin of two recent sample return mission target asteroids, (162173) Ryugu and (101955) Bennu. Methods. We obtain low-resolution visible spectra of target asteroids down to 0.35 μm using the telescopes located at the Roque de los Muchachos Observatory (La Palma, Spain) and revisit spectroscopic data that have already been published. Using new spectroscopic and already published spectrophotometric and spectroscopic data, we study the characteristics of the NUV-VIS reflectance spectra of primitive asteroids, focusing on data of the Themis family and the Polana-Eulalia family complex. Finally, we compare the NUV characteristics of these families with (162173) Ryugu and (101955) Bennu. In this work, we also study systematic effects due to the use of the five commonly used stars in Landolt’s catalog as solar analogs to obtain the asteroid reflectance in the NUV wavelength range. We compare the spectra of five G-stars in Landolt’s catalog with the spectrum of the well-studied solar analog Hyades 64, also observed on the same nights. Results. We find that many widely used Landolt’s G-type stars are not solar analogs in the NUV wavelength spectral region and thus are not suitable for obtaining the reflectance spectra of asteroids. We also find that, even though the Themis family and the PolanaEulalia family complex show a similar blueness at visible wavelengths, the NUV absorption of the Themis family is much deeper than that of the Polana-Eulalia family complex. We did not find significant differences between the New Polana and Eulalia families in terms of the NUV-VIS slope. (162173) Ryugu’s and (101955) Bennu’s spectral characteristics in the NUV-VIS overlaps with those of the Polana-Eulalia family complex which implies that it is the most likely origin of these two near-Earth asteroids.

Benchmarking iSALE and CTH Shock Physics Codes to In Situ High‐Velocity Impact Experiments Into Fe‐Ni Targets

AbstractCratering is a prominent evolutionary process on asteroids. Crater morphologies, regolith generation, bulk fracturing and projectile implantation are all examples of asteroidal surface evolution resulting from impact processes. The characterization of these processes on metal‐rich bodies has become a priority due to the upcoming NASA Psyche mission, poised to study the likely metal‐rich 225‐km main belt asteroid, (16) Psyche. Small‐scale impact experiments into metals (e.g., iron, aluminum, copper, steel) have shown that crater morphologies into these materials are different than rocky targets—exhibiting notable distinctive features such as raised, sharp rims, and deeper cavities. In this work, we determine strength constants for different metals used in prior impact experiments, namely manufactured Fe‐Ni materials and the Gibeon iron meteorite at 77 K. These parameters have been used as inputs for the Johnson and Cook (1983) strength model in a suite of numerical simulations reproducing impact experiments. Using the Johnson and Cook strength model and our laboratory‐derived material constants, we find that it is possible to closely match small‐scale experimental crater diameters and depths using iSALE and CTH shock physics codes.

A sweeping and grinding combined hybrid sampler for asteroid sample return mission

Successful sampling on asteroids is challenging due to their weightless environment and unknown material mechanical properties. This work presents a sweeping and grinding combined hybrid sampler (SGHS) to improve the sampling success rate. The SGHS has two working modes, i.e., using two brush wheels to collect regolith and rock pieces and employing a drill bit to grind rocky surfaces into particles suitable for sweeping. We investigated the sampler-regolith interaction and sample particles contact model and designed the adaptive sampling control method. Numerical simulation and prototypical experiments at different structural parameters and speeds of the brush wheels, mechanical properties of the sample, and asteroid surface gravities, were conducted to validate the proposed methods and estimate the amount and speed of sample collection. The 280 g sampler can acquire 24.12 g regolith simulant in 8 s with the “weight on bit” (WOB) of 0.2 N. The drill bit can enhance the sampling efficiency by 151% in rocky sample simulant acquiring. The results also indicate that sample collection on asteroids is more challenging than sampling on Earth. Moreover, the rotational speed of the SGHS should be carefully controlled to avoid sample particles with too high a speed spilling out of the sampling site. The sampler has the advantages of small size, light weight, low WOB, and high adaptability and can be used for future asteroid sample return missions.

Formation and decomposition of vacancy-rich clinopyroxene in a shocked eucrite: New insights for multiple impact events

Impact is a fundamental process shaping the formation and evolution of planets and asteroids. It is inevitable that some materials on the surface of planets and asteroids have been impacted for many times. However, unambiguous petrological records for multiple post-formation impact events are rarely described. Here, we report that the thin shock melt veins of the shocked eucrite Northwest Africa 8647 are dominated by a fine-grained intergranular or vermicular pigeonite and anorthite assemblage, rather than compact vacancy-rich clinopyroxene. Vacancy-rich clinopyroxene in the veins instead is ubiquitous as irregularly-shaped, relict grains surrounded by intergranular or vermicular pigeonite and anorthite assemblage. The silica fragments entrained in shock melt veins contain a coesite core and a quartz rim. The occurrences of vacancy-rich clinopyroxene and coesite can be best explained by two impact events. The first impact event produced the shock melt veins and lead to the formation of vacancy-rich clinopyroxene and coesite. The second impact event heated the fine-grained melt veins and lead to the widespread partial decomposition of vacancy-rich clinopyroxene and the partial back-transformation of coesite. This paper is the first report of the decomposition reaction of shock-induced vacancy-rich clinopyroxene in extraterrestrial materials. We propose that widespread decomposition and/or back-transformation of high-pressure minerals in shocked meteorites can be considered as important records of multiple impact events.

Alignment of fractures on Bennu’s boulders indicative of rapid asteroid surface evolution

On asteroids, fractures develop due to stresses driven by diurnal temperature variations at spatial scales ranging from sub-millimetres to metres. However, the timescales of such rock fracturing by thermal fatigue are poorly constrained by observations. Here we analyse images of the asteroid (101955) Bennu obtained by the Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer (OSIRIS-REx) mission and show that metre-scale fractures on the boulders exposed at the surface have a preferential meridional orientation, consistent with cracking induced by diurnal temperature variations. Using an analytical model of fracture propagation, we suggest that fractures the length of those on Bennu’s boulders can be produced in 104–105 years. This is a comparable or shorter timescale than mass movement processes that act to expose fresh surfaces and reorient boulders and any preferential direction signature. We propose that boulder surface fracturing happens rapidly compared with the lifetime in near-Earth space of Bennu and other carbonaceous asteroids. The damage due to this space-weathering process has consequences for the material properties of these asteroids, with implications for the preservation of the primordial signature acquired during the accretional phases in the protoplanetary disk of our solar system. Fractures on the asteroid Bennu imaged by the OSIRIS-REx spacecraft are consistent with cracking induced by diurnal temperature variations over geologically rapid timescales.

Quality Assessment of Stereophotoclinometry as a Shape Modeling Method Using a Synthetic Asteroid

The stereophotoclinometry (SPC) software suite has been used to generate global digital terrain models (DTMs) of many asteroids and moons, and was the primary tool used by the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission to model the shape of asteroid Bennu. We describe the dedicated preflight testing of SPC for the OSIRIS-REx mission using a synthetic “truth” asteroid model. SPC has metrics that determine the internal consistency of a DTM, but it was not known how these metrics are related to the absolute accuracy of a DTM, which was important for the operational needs of the mission. The absolute accuracy of an SPC-generated DTM cannot be determined without knowing the truth topography. Consequently, we developed a realistic, but synthetic, computer-generated representation of asteroid Bennu, photographed this synthetic truth model in an imaging campaign similar to that planned for the OSIRIS-REx mission, and then generated a global SPC DTM from these images. We compared the SPC DTM, which was represented by a radius every 70 cm across the asteroid surface, to the synthetic truth model to assess the absolute accuracy. We found that the internal consistency can be used to determine the 3D root-mean-square accuracy of the model to within a factor of two of the absolute accuracy.

Ground Testing of Digital Terrain Models to Prepare for OSIRIS-REx Autonomous Vision Navigation Using Natural Feature Tracking

The OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) spacecraft collected a sample from the asteroid Bennu in 2020. This achievement leveraged an autonomous optical navigation approach called Natural Feature Tracking (NFT). NFT provided spacecraft state updates by correlating asteroid surface features rendered from previously acquired terrain data with images taken by the onboard navigation camera. The success of NFT was the culmination of years of preparation and collaboration to ensure that feature data would meet navigation requirements. This paper presents the findings from ground testing performed prior to the spacecraft's arrival at Bennu, in which synthetic data were used to develop and validate the technical approach for building NFT features. Correlation sensitivity testing using synthetic models of Bennu enabled the team to characterize the terrain properties that worked well for feature correlation, the challenges posed by smoother terrain, and the impact of imaging conditions on correlation performance. The team found that models constructed from image data by means of stereophotoclinometry (SPC) worked better than those constructed from laser altimetry data, except when test image pixel sizes were more than a factor of 2 smaller than those of the images used for SPC, and when topography was underrepresented and resulted in incorrect shadows in rendered features. Degradation of laser altimetry data related to noise and spatial sampling also led to poor correlation performance. Albedo variation was found to be a key contributor to correlation performance; topographic data alone were insufficient for NFT.

Crater size scaling relationship including the armoring effect for application to the surface of rubble-pile asteroids having a boulder size distribution

Crater size scaling relationship including the armoring effect for application to the surface of rubble-pile asteroids having a boulder size distribution

Investigating S-type asteroid surfaces through reflectance spectra of ordinary chondrites

The search for asteroidal parent bodies of chondrites through various techniques is an ongoing endeavor. A link between ordinary chondrites (OCs) and S-type asteroids has previously been established by the sample return of the Hayabusa space mission. OCs are the class with the most abundant samples in our meteorite collection. We present an in-depth study of the reflectance spectra of 39 equilibrated and 41 unequilibrated ordinary chondrites (EOCs and UOCs). We demonstrate that consistent measuring conditions are vital for the direct comparison of spectral features between chondrites, otherwise hampering any conclusions. We include a comparison with a total of 466 S-type asteroid reflectance spectra from various databases. We analyze (i) if a difference between EOCs and UOCs as well as between H, L and LL can be seen, (ii) if it is possible to identify unequilibrated and equilibrated S-type asteroid surfaces and (iii) if we can further constrain the match between OCs and S-type asteroids all based on reflectance spectra.As a first step, we checked the classification of the 31 Antarctic UOCs analyzed in the present work, using petrography and magnetic measurements, and evidenced that 74% of them were misclassified. Reflectance spectra were compared between EOCs and UOCs as well as between H, L and LL chondrites using a set of spectral features including band depths and positions, peak reflectance values, spectral slopes and the Ol/(Ol + Px) ratio. UOCs and EOCs reflectance spectra show no clear-cut dichotomy, but a continuum with some EOCs showing stronger absorption bands and peak reflectance values, while others are comparable to UOCs. Moreover, we show by the example of 6 EOCs that their band depths decrease with decreasing grain size. Based on reflectance spectra alone, it is thus highly challenging to objectively identify an unequilibrated from an equilibrated S-type surface. There is no clear distinction of the chemical groups: only LL EOCs of petrographic type >4 can be distinguished from H and L through less deep 2000 nm band depths and 1000 nm band positions at longer wavelengths. No dichotomy of S-type asteroids can be seen based on the Ol/(Ol + Px) ratio. Their average Ol/(Ol + Px) ratio matches EOCs better than UOCs. A principal component analysis (PCA) was performed illustrating that both the unknown degree of space weathering and the unknown regolith grain size on asteroid surfaces hinder the distinction between equilibrated and unequilibrated surfaces. Lastly, an anti-correlation between the diameter of the asteroids and their 1000 nm band depth is found indicating that larger sized S-type asteroids show finer grained surfaces.

Stochastic Models and Control of Anchoring Mechanisms for Grasping in Microgravity

Robots equipped with anchoring mechanisms have attractive applications in asteroid exploration. However, complex application scenarios bring great challenges to the modeling and control of anchoring mechanisms. This paper presents a grasping model and control method for an anchoring mechanism for asteroid exploration. First, the structure of the anchoring mechanism is demonstrated. Second, stochastic grasping models based on surface properties are established. The effectiveness of the grasping model is verified by experiments. A stiffness-modeling method of the microspine is proposed. On this basis, the stochastic grasping model of the anchoring mechanism is established, and the grasping cloud diagram of the anchoring mechanism is drawn. Third, in order to reduce the collision force between the anchor mechanism and the asteroid surface, a control method for the anchoring mechanism in the movement process is proposed based on the motion mode of the asteroid-exploration robot. Finally, a prototype is developed, and the experimental results validate the motion ability of the robot and the control method.

Gas-driven asteroid regolith sampling device based on disk-shaped cutter

The gas-driven and disk cutting sampling method are of considerable significance to avoid the limitation of sampling in the low-gravity environment of the asteroid and directly collect dust and gravel samples on the surface of the asteroid. A new mechanical structure of the gas-driven and disk cutting sampling device is proposed in this paper, which mainly consists of two parts: the air-blowing device and the disk-shaped cutter. In this design, the disk-shaped cutter is used to cut rocks on the asteroid surface and the air-blowing device is used to blow and take the rubble samples on the asteroid surface. Based on the CFD-DEM co-simulation method, the structural parameters of the air blowing device were compared and optimized by the velocity of the airflow, which is considered as the measurement index. According to the simulation results, the structure of the nozzle of the air-blowing device is designed, and a series of air blowing experiments were carried out to verify the accuracy of CFD-DEM co-simulation results. Subsequently, further experiments proved the device's sampling ability on uneven ground. It is found in this paper that this device can sample volcanic rock particles in the range of 5–15 ​mm and 15–25 ​mm. Therefore, it is feasible to collect samples on the asteroid surface by the gas-driven and disk cutting sampling method.

Diverse space weathering effects on asteroid surfaces as inferred via laser irradiation of meteorites

Context. Space weathering (SW) is crucial to improve the understanding of the evolution of optical characteristics on airless bodies. The classical view based on research of the Moon suggests that SW decreases albedo (darkening) and steepens spectral slope (reddening) in visible to near-infrared (VIS-NIR) wavelengths, producing nanophase iron (npFe0). However, this conclusion is not perfectly applicable to asteroids. Aims. In this study, we focus on investigating the space weathering spectral alteration effects (SWSAE) and the causes of spectral alteration on various types of asteroids after long-term continuous micrometeoroid bombardments. Methods. We used a pulsed laser to irradiate eight meteorites at the same energy, namely, of 28 mJ, in ten shots, including ordinary chondrites (OCs), aubrite (Aub), enstatite chondrites (ECs), CO, CV, and CM carbonaceous chondrites. Then we measured and compared the virgin and irradiated VIS-NIR reflectance spectra of these meteorites. We further surveyed the causes of spectral alteration through a scanning electron microscope and transmission electron microscope. Results. Three different SWSAE are shown: (1) darkening and reddening on OCs, Aub, CO, and CV chondrites; (2) brightening and reddening on ECs; (3) brightening and bluing on CM chondrite. After irradiation, npFe0 and nanophase iron-nickel particles were respectively found in CV and CO chondrites; thick amorphous layers without any nanophase particles were found in Aub; melting and sputtering of metal were observed in ECs; a great deal of vesicles or bubbles without any nanophase particles were found in CM chondrite. Conclusions. The long-term SW via micrometeoroid bombardments can spectrally remodel asteroid surfaces in different ways: darken and redden anhydrous silicate asteroids (e.g., S-, E-, and K-types); brighten and redden metal-rich M-type objects. The SWSAE of volatiles-rich carbonaceous asteroids (e.g., Ch-, Cgh-, and D-types) is related to SW degree: darkening and bluing at low degree then brightening and continue bluing as the SW degree increases. The various spectral units on Ryugu, Bennu, and Phobos can be created by the heterogeneity of the degree of SW.

Numerical approach to synthesizing realistic asteroid surfaces from morphological parameters

Context. The complex shape of asteroids and comets is a critical parameter in many scientific and operational studies. From the global irregular shape down to the local surface details, these topographies reflect the formation and evolutionary processes that remould the celestial body. Furthermore, these processes control how the surface will continue to evolve: from mass wasting on high slopes to spin-up due to anisotropic re-emission of thermal radiation. In addition, for space missions, the irregular coarse shape and complex landscape are a hazard to navigation, which must be accounted for in the planning phase. Aims. In this paper, we propose a novel method to synthesize physically correct 3D shape models of small celestial bodies, such as asteroids, to support the testing of a wide range of parameters in scientific and operational studies. Methods. We modeled virtual asteroid shapes using non-uniform sphere packings to represent the coarse shape, define an implicit surface, and then synthesize high-resolution topography with user-defined, locally controlled spot noise models. This effectively replaces the random noise model (e.g., Perlin noise) used in traditional approaches and allows us to construct a morphology based on actual physical shapes of the most common features observed on asteroids and comets. As an example of such a feature, we propose several kernel functions to add virtual craters to the coarse shape of the asteroid, of which the spatial distribution is controlled by typical crater production functions (e.g., a power law). Results. We demonstrate how this technique can be used to generate a variety of asteroid shapes and topographies using different cratering parameters and distributions. We apply our technique to artificially increase the resolution of existing models of the Didymos-Dimorphos system, the target of the Double Asteroid Redirection Test, and Hera missions. We show that our approach generates models that are suitable for typical analysis relying on detailed asteroid shapes, as well as operational scenarios for space missions. The meshes created with our algorithm can be directly used with existing visualization software and operations or science pipelines to generate data suitable for mission planning and to validate data analysis techniques.