As comets draw closer to the Sun, they begin to emit small solid particles, producing the familiar dust coma and tail. The cohesive forces binding these micrometer-sized grains typically reach about 1 kPa, while the gas pressure generated by sublimating volatiles usually remains only a few pascals. This stark difference presents a major challenge: any plausible dust release model must explain how such strong cohesion between particles can be overcome.

Cohesion can be effectively reduced only under particular conditions. One such scenario involves the formation of weakly bound porous aggregates — cometary "pebbles" — composed of fine micron-sized dust grains assembled into millimeter-sized structures. This concept aligns well with in situ findings from the COSIMA, MIDAS, and GIADA instruments. A theoretical model proposed by Skorov and Blum (2012) describes the removal of these porous aggregates through sublimation-driven gas flow, and subsequent laboratory experiments have confirmed the validity of this mechanism.

Earlier models, including related approaches, generally assumed the presence of a dry, porous dust crust situated above an icy substrate, with sublimating gases accumulating pressure at the ice-dust boundary. In these models, it is primarily fragments of the crust — rather than individual grains — that are detached and ejected into space. More recently, however, new models have emerged, focusing instead on the possibility of releasing primary dust particles or small aggregates (Schuckhart & Blum, 2025).

In this study, we extend this perspective by investigating the evolutionary dynamics of a densely packed, heterogeneous porous layer consisting of non-volatile dust grains intermixed with icy inclusions, subjected to solar heating. The absorption of solar radiation triggers the sublimation of the embedded ice, which progressively weakens the mechanical integrity of the porous structure and drives its spatial reorganization.

To simulate these processes, we develop a novel computational framework based on the DEM that explicitly represents the granular structure of the heterogeneous material (Reshetnyk et al. 2025). Our study examines systems composed of both solid particles and porous aggregates, considering arrangements of both monodisperse and polydisperse spheres. Two formation scenarios are analyzed: layers resulting from initial deposition and those compacted under external mechanical loads. Particular attention is devoted to the phenomenon of jamming, where compression immobilizes the particles into a dense, stable configuration.

Using tools from percolation theory and graph analysis, we map the pathways leading to material disintegration. Our results demonstrate that the sublimation of internal ice can promote the detachment and ejection of individual dust grains or small clusters from the cometary surface. Unlike traditional approaches that focus on the global tensile strength of the dust layer, our model emphasizes localized release mechanisms, offering new insights into the origin of fine dust observed in cometary environments. Additionally, we find that some of the ejected aggregates may retain residual ice, potentially serving as a prolonged source of both dust and water vapor — a result consistent with observations of comet 67P/Churyumov-Gerasimenko.

References:

Reshetnyk, V. et al. 2025. Key structural characteristics of porous layers in diffusion modelling: A study on polydispersity, shape, and hierarchy. PSS 260. doi:10.1016/j.pss.2025.106078

Schuckart , C. and J. Blum 2025. A&A, doi: 10.1051/0004-6361/202553750

Skorov, Y. and J. Blum. 2012. Dust release and tensile strength of the non-volatile layer of cometary nuclei. Icarus 221, 1–11. doi:10.1016/j.icarus.2012.01.012

How to cite: Skorov, Y., Reshetnyk, V., Lukyanyk, I., Schuckart, C., and Blum, J.: Evolution of Micro-Granular Porous Dust-Ice Mixtures Under Solar Irradiation: Implications for Cometary Dust Activity, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-195, https://doi.org/10.5194/epsc-dps2025-195, 2025.

Comets and their surface are mixtures of refractory and icy material. Space missions like Rosseta gave estimates on how much ice is present at a comet on global scale. On local (millimetre to micrometre) scale the distribution of ices inside the porous regolithic structure is less well understood. Nevertheless, in active periods the distribution of ices might change the thermodynamic behaviour and thereby affect global outgassing rates and dust activity. To address this, we developed a one-dimensional thermophysical outgassing model, which allows to simulate gas activity depending on the chosen structural model. For now, we consider two possible porous structures, one where ice is located around agglomerates filling the larger macropores and another where the ice is present within the agglomerate, which affects the gas diffusivity less.  The thermophysical model couples the heat and gas diffusion equations and allows ices to sublimate and redeposit depending on the local temperature and pressure. Figure 1 illustrates the simulated desiccation process, hence how the ice content φ changes with time and depth when the irradiation is assumed to be constant. The front (shaded regions) moves deeper with time as no dust activity is assumed. We find that a part of the sublimated material does redeposit in deeper layers forming a layer of high ice fraction (sinter layer), which is visible as a region where the ice content exceeds the initial 10 %. Simulations of single agglomerates show that most of the additional ice will freeze out in the larger pores around the agglomerate, thereby clogging the pore space beneath. We further discuss the effects of the different models on the thermal conductivity and analyse properties of a forming sublimation front.

How to cite: Zivithal, S., Macher, W., Kargl, G., and Lammer, H.: The desiccation process of cometary surfaces , EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-522, https://doi.org/10.5194/epsc-dps2025-522, 2025.

Non-gravitational effects serve as a critical nexus between comet dynamics and thermodynamics, offering essential insights into cometary activity and evolution. While sublimation-driven recoil forces influence both orbital and rotational motion, these effects simultaneously encode critical information about a comet’s physical properties. Comet 103P/Hartley 2 exhibits pronounced non-gravitational torque-driven rotation during perihelion passage. This study employs observational spin-state variation data to inversely constrain the H₂O and CO₂ ice sublimation depths across surface regions and investigates long-term rotational evolution.

We present a coupled attitude-thermal simulation framework integrating nucleus thermal modeling with rotational dynamics simulations. The dust mantle model is used to simulate the one-dimensional thermal process of the cometary nucleus surface. In this model, volatiles sublimate from a certain depth on the nucleus surface. By setting different ice front depths for various regions, we can model the anisotropic sublimation on the cometary nucleus. To address computational bottlenecks, we implement a neural network proxy model achieving 60-fold acceleration with a relative error of 13%. Based on observation results, the nucleus is divided into three regions: the large end, the waist, and the small end. CO₂ ice sublimates from the ends, while H₂O ice sublimates from the waist. By treating sublimation depth as optimizable variables, we successfully reproduce 103P’s observed spin-state variations and volatile production rates.

Key results demonstrate:

• The angular momentum and rotational energy of the nucleus exhibit a combination of short-term fluctuations and long-term decay (Fig. 1).
• Sublimation patterns at E+7 min show H₂O release from the waist and asymmetric CO₂ outgassing – predominantly from the sunlit small lobe with secondary production on the large lobe's nightside. Extended analysis reveals that the dust mantle layer acts as a thermal insulator, maintaining sustained volatile sublimation throughout the nucleus's rotational cycle. Derived CO₂ ice front depths are 71 mm (large lobe) and 92 mm (small lobe), with the large end showing stronger activity. While modeled CO₂ production (1.77×10²⁷ mole/s) matches observations, waist H₂O production (4.93×10²⁶ mole/s) constitutes merely 5% of observed values, suggesting H₂O production rate mainly originates from CO₂-driven water ice ejection at the ends.
• Long-term simulations predict initial short-axis excitation transitioning to long-axis mode around E-200 days. In the following orbital cycles, the nucleus’s angular momentum gradually shifted toward the minimum inertia axis, and a sun-pointing attitude emerged. Each time the nucleus passes through perihelion, the angular velocity increases. We estimate that 103P may reach its rotational break-up limit after approximately 25 orbital cycles.

Fig. 1: Variations in angular momentum and rotational energy. The upper graph shows the angular momentum variation, and the lower graph shows the rotational energy variation. The black crosses represent Belton’s estimates, and the red curve represents the fitting results from this study.

How to cite: Liu, J., Tang, Y., Wang, X., and Yue, Y.: Unravelling Anisotropic Sublimation Effects on Comet 103P/Hartley 2 through Coupled Attitude-Thermal Simulations, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-466, https://doi.org/10.5194/epsc-dps2025-466, 2025.

Simulating cometary activity by overcoming material cohesion in order to eject dust particles is currently challenging for numerical models. Here we will present the results of a pebble-based 1D thermophsical model running across a number of points on the surface of comet 67P/Churyumov-Gerasimenko (hereafter 67P). We find that, for sufficiently low diffusivities,  the cohesion can be overcome by sublimating gas pressure build-up in the subsurface, leading to the ejection of the dust crust and resulting in global emission rates of dust, water, CO₂, and CO that roughly match those observed by the Rosetta mission. Ejected particles are of millimetre- to decimetre-scale, and all come from the southern hemisphere during the time that it is strongly illuminated at perihelion, leading to the 'blow-off' of the dust-crust here. Volatiles are then much closer to the surface in the south (within the top centimetre) than in the north (10 or more cm deep), naturally explaining the strong water outgassing expected here from modelling of 67P's non-gravitational accelerations and torques. We find that a low gas-diffusivity, as well as a large heat-capacity and a steeply decreasing tensile strength with depth, are in best agreement with the outgassing data. However, the model struggles not to exceed the observed emission rates of dust, CO₂, and CO. It is difficult to achieve a balance between triggering activity and generating too much of it in the south (with CO₂ the critical driving-species here); while in the north, it remains challenging to generate activity at all. The local and global locations of dust ejection and erosion place strong constraints on the nature of the cometary activity mechanism.

How to cite: Attree, N., Gutiérrez, P., Schuckart, C., Blum, J., Markkanen, J., and Skorov, Y.: Modelling comet 67P/Churyumov-Gerasimenko's global production rates with an ejecting dust-crust, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-19, https://doi.org/10.5194/epsc-dps2025-19, 2025.

Comets are among the most primitive objects in the solar system, acting as time capsules that preserve clues about the solar system’s origins and early evolution. These icy bodies store volatile compounds that are sporadically released, offering a window into their internal structure and composition. Among the mechanisms of volatile release, outbursts stand out as the most extreme and energetic, marked by sudden brightness increases and the ejection of vast amounts of material into space (Lin et al., 2009; Lin et al., 2017; Vincent et al., 2016). Such explosive events have been observed on a range of cometary bodies—including Jupiter-family comets (Li et al., 2011), centaurs (Donaldson, A., & Scholz, A. 2020), and dynamically new comets (Combi et al. 2019)—and occur under diverse conditions: at perihelion and aphelion, and during midday and/or local night(Rousselot, 2008; Vincent et al., 2016).

     Despite their dramatic nature and scientific importance, the mechanisms driving outbursts and their effects on a comet’s surface morphology remain poorly understood. ESA’s Rosetta mission provided over two years of unprecedented observations of Comet 67P/Churyumov–Gerasimenko (67P), capturing dozens of outbursts throughout the comet’s perihelion passage (Vincent et al., 2016). However, studying the impact of these outbursts on 67P’s surface presents unique challenges due to the comet’s complex bilobate shape, which complicates observation and analyses. This challenge is highlighted by the fact that while 34 major outbursts near perihelion were identified (Vincent et al., 2016), only 6 outburst-associated surface changes were documented prior to this study (Pajola et al., 2017; Fornasier et al. 2017; El-Maarry et al., 2019; Hasselmann et al., 2019). 

     To bridge this gap, we have developed a new tool–the Rosetta Search and Characterization Tool (RoSCo) that allows selecting a region of interest on a 3D shape model of 67P and retrieval of all associated images, followed by precise projection of all images into any user-defined coordinate system. Using RoSCo, we are mapping outburst-driven changes in high-resolution detail and will present a comprehensive analysis of how these energetic events reshape cometary terrain. The results demonstrate that cliff collapses, pit formation, and smooth terrain loss are all capable of sourcing such events. These cascading surface transformations offer critical constraints for refining models of cometary dynamics, volatile redistribution, and long-term landscape evolution. In this presentation, we will present all of our new findings and what our ongoing work will be to fully characterize these most dramatic of comet-shaping events.

How to cite: Moser, M., Jindal, A., Birch, S., Fouché, E., Soderblom, J., Vincent, J.-B., Steckloff, J., Davidsson, B., Marschall, R., and Umurhan, O.: Kaboom: Surface Manifestations of Cometary Outbursts, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-868, https://doi.org/10.5194/epsc-dps2025-868, 2025.

Introduction:  Coma images of active comets are commonly used to identify inhomogeneities that appear as coma features, which provide key insights into coma dynamics and nucleus properties [e.g., 1, 2]. We have developed a 3D Monte Carlo model to simulate such features and have successfully applied it to interpret cometary activity and nucleus characteristics in prior studies [e.g., 3, 4, 5]. We are currently preparing to release this software as a Tool to the wider astronomy community via a user-friendly web interface, Coma Factory. A companion Python package containing the underlying codes will also be made available. Our presentation will include a live demonstration of Coma Factory using both the web interface and the Python package in a Jupyter Notebook. We welcome community feedback to help guide the development of comprehensive tutorials and ensure the Tool’s broad utility.

Coma Model:  The 3D Monte Carlo coma model simulates the spatial distribution of particles – first-, second-, or third-generation species – emitted from a nucleus. The resulting 3D particle distribution is then projected onto a 2D skyplane corresponding to the observer’s line of sight (e.g., Figure 1), enabling direct comparison with observed coma images. The model requires input parameters that describe the comet’s activity, nucleus properties, particle-specific species characteristics, and observing geometry. It also includes the capability to simulate the effects of solar radiation pressure on all species.

Coma Factory: When using Coma Factory, once the user provides the necessary input parameters, the web interface runs the Python code to generate the corresponding image in FITS format. The image header includes keywords identifying all the input parameters and hence each image created by Coma Factory maintains a digital record of the input parameters corresponding to each image. Additionally, Coma Factory may be used to produce 2D coma simulations corresponding to a range of viewing directions that enable the user to assess the 3D structure of the coma feature(s) that are useful for interpreting actual coma observations of comets.

Figure 1. Top-left: Image of the active Centaur 2023 RS₆₁ from [6]. Top-right: shown is a simulated image using Coma Factory that is consistent with the data.  The bottom two panels show the same simulated image but if the data had been acquired with other facilities with different image resolutions. The same coma model was used for each of the three image simulations, where characteristics of each telescope and instrument combination were used to replicate imaging data if observations had been acquired from the specified facility. Coma Factory is capable of generating realistic comae images as illustrated by these simulations.

Acknowledgments: We gratefully acknowledge the support provided by the NASA PDART Program through award 80NSSC21K0881.

References:  [1] Schleicher D. G. and Woodney L. M. (2003) Icarus, 162, 190-213. [2] Goldberg C. et al. (2023) Planet. Sci. J., 4, 19pp. [3] Schulz R. et al. (1993) Icarus, 103, 319-328. [4] Samarasinha N.H. (2000) Astrophys. J., 529, L107-L110. [5] Schambeau C. A. et al. (2017) Icarus, 284,359-371. [6] Lilly et al. (2025) RNAAS, 9, Issue 3, id.67.

How to cite: Schambeau, C., Samarasinha, N., Gay, P., and Bauer, I.: Simulating and Analyzing Comet Comae with Coma Factory, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-825, https://doi.org/10.5194/epsc-dps2025-825, 2025.

Understanding the morphology and dynamics of cometary gas jets is essential for interpreting optical observations, planning flyby, rendezvous and impact trajectories and inferring subsurface volatile emissions. However, conventional high fidelity gas and dust models require substantial computational resources, specialized software and offline rendering pipelines. We present a web browser native framework that enables real time interactive simulations and visualizations of cometary outgassing for arbitrary nucleus shapes, requiring minimal setup running on a local graphics processing unit (GPU) powered by WebGPU technology [1] .

The developed processing pipeline implements the nucleus surface thermal balancing solver adapted from the Space Imaging Simulator for Proximity Operations (SISPO) [2] ComaCreator module and research done by Marschall et al. [3]. This yields spatially resolved sublimation rates that identify active regions depending on the angle of incidence onto the nucleus. Due to the fact that the thermal balance and gas emission calculations are carried out on a per facet basis, the pipeline is agnostic to object geometry therefore any cosmic object represented as a triangular surface mesh at any resolution can be processed without modification. As we obtain surface emission rates, WebGPU integration allows for sophisticated determination of activity generation for cometary jets. Example parameters determined by the surface activity levels include emission rates, particle sizes and lifetime, directional spread and emission velocity. Since technology comes with a provided shading language, it is possible to leverage GPU capabilities in order to determine the movement of dust particles using compute shaders based on physical equations present in observed flyby scenarios.

Our current implementation of the web-based cometary activity model includes two modes - particle based and direction line based. This allows the user to tailor the simulation to specific scientific needs - streamlines allow for dust flow path visualization and jet trajectories, useful for quantitative analysis of jet origins and orientations while particle approach captures volumetric scattering and diffuse coma structures, offering realistic depiction of gas density variance and illumination effects. The interface is tailored with configuration parameters, which may be changed in real time to simulate various scenarios of comet activity. Adjusting any configuration re-runs the simulation nearly instantaneously, fostering rapid testing and analysis without recompilation or preprocessing. Preliminary results are showcased in figure 1 and 2, displaying potential approaches to jet formation and dust dissipation visualization.

By developing a tool to perform cometary activity research on any modern browser, we empower mission planners, observers and educators to explore the cometary outgassing phenomena on various discovered or procedurally generated nuclei. It also serves as a tool to popularize and educate the public on the complex nature of cometary activity and dust emission in space.

References
[1] https://www.w3.org/TR/webgpu/
[2] M. Pajusalu et al. (2022) SISPO: Space Imaging Simulator for Proximity Operations. PLoS ONE 17(3): e0263882. https://doi.org/10.1371/journal.pone.0263882
[3] R.В  Marschall et al. (2016) Modelling observations of the inner gas and dust coma of comet 67P/Churyumov-Gerasimenko using ROSINA/COPS and OSIRIS data: First results A&A 589 A90. https://doi.org/10.1051/0004-6361/201628085

How to cite: Jasmonts, G., Slavinskis, A., and Šķirmante, K.: Development of an Interactive Web-Based Simulation and Visualization Tool for Cometary Jet Modelling on Arbitrarily Shaped Nuclei, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1940, https://doi.org/10.5194/epsc-dps2025-1940, 2025.

This work presents a microgravity experimental campaign aimed at investigating contact dynamics in asteroid-like environments. Recent Earth-based and in-situ observations have revealed that most asteroids between a few hundred meters and several kilometers in diameter are not monolithic, but rather loosely bound aggregates of material - commonly referred to as rubble piles [1]. These bodies are held together by a combination of self-gravity and cohesion forces. Results in literature show that their dynamics can be effectively simulated by addressing a gravitational-collision problem via N-body codes [2]. The contact representation relies on a set of parameters, such as friction and coefficient of restitution, that are typically calibrated to match large-scale behaviours rather than the local contact dynamics. Hence, an experimental campaign has been performed to validate at particle scale the N-body code GRAINS, whose contact dynamics is based on the physics engine Chrono. The experiment involved observing low-speed collisions between two asteroid-simulant cobbles under microgravity conditions. The 6-degree-of-freedom trajectories of the cobbles were reconstructed, and a digital twin of the experiment was created in GRAINS to calibrate the contact parameters against the experimental results.

The campaign, sponsored by ESA, was performed at ZARM facilities, exploiting both the Drop Tower and the GraviTower Bremen Pro. The first can offer one of the best microgravity environments worldwide (10^-6 g₀) for 4.7 s, allowing for 2–3 tests per day. In the latter, despite a slightly larger residual acceleration (10^-4 g₀) and shorter duration, tens of drops per day can be performed [3]. The first half of the campaign took place between October/November 2024; the second half took place between March/April 2025.

To replicate the physical characteristics of asteroid material, cobbles were selected based on their chemical composition and surface texture. Two high-fidelity simulant sets have been purchased from Space Resource Technology, with mineralogy modelled after the Murchison (CM simulants) and Orgueil (CI simulants) meteorites [4]. An additional set has been sampled on Mount Etna: coming from recent volcanic eruptions, they present the irregular and un-weathered surface expected for rocks found on Solar System bodies without an atmosphere. To recover the shape and inertia properties of each cobble, they have been scanned using a 3D scanner with 0.035 mm accuracy. The mesh obtained is used to build the digital twin of the experiment. Markers have been glued to the surface of the cobbles to enable motion tracking and trajectory reconstruction.

Figure 1: 3D scanner.

The experiment is placed inside a vacuum chamber, since, besides microgravity, vacuum conditions are fundamental to simulate the asteroid environment. The cobbles are released using a spring-based release mechanism with a velocity in the range 15 – 20 cm/s. Their motion was recorded using a network of two high-speed cameras provided by ZARM, along with three GoPro cameras mounted inside the chamber to ensure full visual coverage (see Figure 2). The high-speed cameras could observe the interior only through a mirror, due to the limited available space.

Figure 2: experimental setup.

The tracked markers’ coordinates are processed in a batch least-squares filter to reconstruct the cobbles’ 6-dof trajectory and provide the digital twin with the initial conditions, necessary to validate the numerical code. This analysis also enables the computation of key parameters for characterizing collision dynamics in asteroid environments, such as the coefficient of restitution. Figure 3 shows the tracked markers, whereas Figure 4 shows the reconstructed centre-of-mass trajectory and body triad reprojected into the camera plane.

Figure 3: Tracked markers from GoPro (left) and high-speed camera (right) relative to an Etna rock – CM simulant collision.

Figure 4: pre- (up) and post-collision (down) trajectory reprojected into the camera plane.

In Tab. 1 a summary of the tests performed is reported.

Table 1: Experimental campaign summary.

Tests performed in the GraviTower were useful to tune parameters such as spring stiffness and pre-load. The heritage from the first campaign helped to improve both the total number of tests and success rate. Data quality also improved, thanks to enhanced camera mounting, better visibility, and the use of smaller tracking markers.

The accuracy of the trajectory estimation is assessed through Monte-Carlo simulations, with uncertainties in the order of 0.3 mm in position and 1 deg/s in angular velocity. The coefficient of restitution, computed as the ratio between the energy after and before the collision, including the rotational component, ranges between 0.84 and 0.88. This indicates a nearly rigid contact behavior, suggesting that nearly rigid contact models are best suited to simulate these interactions.

The experimental validation campaign enhances our capabilities to simulate the dynamics of rubble-pile asteroids. This is beneficial not only for the scientific community, but also to support the design of interaction scenarios in upcoming asteroid exploration missions.

References

[1] Walsh K. J. (2018) Rubble Pile Asteroids, Annual Review of Astronomy and Astrophysics., 56, 593–624.

[2] Ferrari F. et al. (2020). A parallel-GPU code for asteroid aggregation problems with angular particles. Monthly notices of the Royal Astronomical society., 492, 749–761.

[3] Könemann T. (2022) Bremen Drop Tower, Version 1.4.

[4] Britt, D.T., et al. (2019), Simulated asteroid materials based on carbonaceous chondrite mineralogies. Meteorit Planet Sci, 54: 2067-2082. https://doi.org/10.1111/maps.13345

Acknowledgements Funded by the European Union (ERC, TRACES, 101077758). Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them.

The GEMS campaign was funded by the European Space Agency under the SciSpace CORA program. The authors would like to acknowledge Thorben Könemann and the ZARM team for their support during the design and operations of the experiment.

How to cite: Vaghi, S., Cremasco, A., Delfanti, L. V., Civati, L. F., Fodde, I., San Sebastiàn, I. L., and Ferrari, F.: Microgravity Experimental Campaign for Contact Dynamics Characterization in the Asteroid Environment, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1599, https://doi.org/10.5194/epsc-dps2025-1599, 2025.

Circumasteroidal debris disks offer an explanation for the surprising existence of atypically shaped binary asteroid satellites [1], such as the oblate Dimorphos imaged by NASA's Double Asteroid Redirection Test (DART) spacecraft [2], or the contact binary satellite Selam detected by Lucy [3]. Classical theories based on the slow build-up of material in orbit around a rapidly spinning primary [4] or contact binary fission [5] account for the predominantly prolate (elongated) population [6], but not any outlier structures. In our work, we used polyhedral N-body simulations to show that the dynamical environment of debris disks around rubble pile asteroids produces mergers between moonlets in the unexplored sub-escape-velocity regime which can create a wide range of unusual satellite shapes.

Spinning rubble pile asteroids only held together by gravity structurally fail before any wide debris disk can be formed, but adding a small amount of cohesion can allow them to reach significantly higher spin rates [7], leading to more chaotic mass-shedding events. Just a few per cent of the primary mass in a disk extending beyond the fluid Roche limit is enough to generate multiple moonlets of varying sizes that dynamically interact and merge [1]. More eccentric orbits are dampened by the surrounding matter, causing mergers to occur with small impact angles. As the typical impact velocity is proportional to the ratio between the total mass of the moons and the mass of the primary [8], the observed impact velocities in simulations of this scenario are always lower than the mutual escape velocity of the moonlets [1].

Because of the soft impacts, the initial shape of the participating moonlets is largely retained, with the most massive specimen being prolate due to tidal distortion. To show that the final shape is highly dependent on the relative orientation of the two bodies and the location of the impact, we performed a set of simulations based on a merger observed in a debris disk scenario (see [1]). Keeping the impact angle, velocity, spin rate, and position of the merger intact, we rotated the most massive body in the equatorial plane of the primary around its barycenter by different angles α to generate a set of new configurations, illustrated in Figure 1. As expected, each merger led to a unique shape, as seen in Figure 2.

Figure 1: Alteration of the initial merger configuration seen on the left side by rotating the largest moonlet (blue) by some angle α, generating new initial conditions [9].

Figure 2:  Post-merger shapes of the merged moonlets, where α indicates the counterclockwise rotation of the largest moonlet (blue) with respect to the original configuration of the merger [9]. The black arrow indicates the direction of the primary.

Letting the system evolve for a few orbits, we found that each body deformed with varying degrees via tidal disruption and distortion, depending on the initial shape and spin-orbit state of the body. Elongated objects were more susceptible to disruption, leaving only the outer lobe intact on a hyperbolic orbit. On the other hand, the more compact objects would instead undergo partial mass-shedding. To consistently have moons survive the tidal disruption stage, we increased the post-merger distance from the primary by 10%. Among the resulting shapes in Figure 3, we can identify spherically oblate Dimorphos-like (α = 15°) and elongated, bilobate Selam-like objects (α = 225°). 

Figure 3:  The shapes of the moons in Figure 1 after 48 h of simulation, for the case where their post-merger distance from the primary was increased by 10% [9].

Our results further reinforce the idea that objects like Dimorphos and Selam have formed in circumasteroidal debris disks and further hint at the existence of other, atypically shaped binary asteroid satellites born from sub-escape-velocity mergers. With the upcoming ESA Hera mission that will revisit the Didymos system [10], along with future space missions visiting binary asteroid systems, we can constrain moon shapes and develop our understanding of the underlying formation mechanisms at play.

Acknowledgments

J.W. and F.F. acknowledge funding from the Swiss National Science Foundation (SNSF) Ambizione grant No. 193346. M.J. acknowledges support from SNSF project No. 200021_207359.

References

[1] Wimarsson et al. Icarus, 421, 116223, 2024

[2] Daly et al. Nature, 616(7957):443–447, 2023

[3] Levison et al. Nature, 629, 1015, 2024

[4] Walsh et al. Nature, 454(7201):188–191, 2008

[5] Jacobson and Scheeres. Icarus, 214(1):161–178, 2011

[6] Pravec et al. Icarus, 267, 267, 2016

[7] Hirabayashi et al. ApJ, 808(1):63, 2015

[8] Leleu et al. Nature Astronomy, 2, 555, 2018

[9] Wimarsson et al., submitted, 2025

[10] Michel et al. PSJ, 3(7):160, 2022

How to cite: Wimarsson, J., Ferrari, F., and Jutzi, M.: Forming unusually shaped moons in binary asteroid systems via sub-escape-velocity mergers and tidal deformation, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-790, https://doi.org/10.5194/epsc-dps2025-790, 2025.

We present a study into the dynamics and evolution of small Solar System bodies. This is the culmination of a PhD which focused on the application of N-body simulations of near-Earth asteroid and interplanetary dust clusters.

This work is split into three projects, which applied N-body simulations of 100 – 1000 particle clusters with a spread up to a maximum velocity. These represented the outcome of an asteroid breakup, with the mechanism represented by the magnitude of the initial spread of the cluster. For the parts of the work which simulated dust, Poynting-Robertson drag (PR drag) was added as an additional force, where each particle was assigned a size and corresponding drag strength.

The first project studied the evolution of synthetic NEA families. As we approach first light of the Vera C. Rubin telescope’s Legacy Survey of Space and Time, with maybe 100,000 new near-Earth asteroids (NEAs) to be discovered [1], it is important to prepare for new searches for NEA families. This project is intended as a guide, so that families and pairs can be searched for where they’re likely to stay closer together for longer. If found, these families can tell us a great deal about the dynamics, composition, and formation of asteroids [2][3]. 

A grid of clusters were integrated with different initial orbital elements and conditions. Areas of focus included initial inclination, breakup mechanism, Kozai-Lidov oscillations, and mean-motion resonances (MMRs). A power-law relationship was found in the increase in orbital dispersion of the semi-major axis, allowing an easier comparison between different initial conditions. This further led us to find the importance of eccentricity and inclination, and how it has an effect on the oscillations caused by the Kozai-Lidov effect.

The second project looked at the hypothetical breakup of an Earth co-orbital – an object in the 1:1 MMR with the Earth. The zodiacal light, or zodiacal dust, is a band of light visible at dusk or dawn when observed close to the plane of the ecliptic [4]. It is caused by the presence of interplanetary dust which scatters the light from the Sun. The zodiacal light has different components identified by spacecraft such as IRAS and COBE [5], including a broad, cometary band, and background interstellar dust. Two strong narrow asteroidal features have also been identified at 士1.4^॰ and 士10.2^॰ ecliptic latitude, as well as a broader band centred at 士10^॰[6]. There have been a number of suggestions as to the exact origin of the asteroid dust bands, most often the scattering of main-belt asteroid families falling into Jupiter resonances [7]. One major factor affecting the evolution of the dust is PR drag, which causes it to spiral into the Sun, requiring the dust to either be regularly replenished, or temporary [8].

We integrated synthetic clusters in the horseshoe, trojan, and quasi-satellite co-orbital configurations, as well as clusters at the position of real Earth co-orbitals. We studied the different factors which affect the infall time and how long dust remains within a co-orbital, along with the appearance of the dust from the Earth, based on how much light is scattered. While no features matching the zodiacal dust bands have been found, we present a quasi-satellite region which is stable for longer periods of time than expected. We also show that while a lot of dust will fall unimpeded into the Sun due to PR drag, some will get trapped in MMRs of terrestrial planets, slowing their infall rate.

The third project looks at the evolution of dust from a hypothetical impact on the Martian trojan (5261) Eureka. A large amount of dust, both interplanetary in the orbital plane of Mars and high up in the Martian atmosphere has been detected by the Juno and MAVEN (The Mars Atmosphere and Volatile Evolution) spacecraft [9][10]. Its properties and quantity cannot be explained by dust storms on Mars, as it is too high in the atmosphere, and is too spread in inclination to originate from the moons Phobos and Deimos.

The dynamics of this dust under the effects of the co-orbital resonance, PR drag, and the gravitational influence of the terrestrial planets has been studied. The minimum orbital intersection distance between the dust and Mars has been calculated, and the orbital dynamics and infall time of the dust studied. The dust seems to stay within the resonance for long periods of time, though PR drag acts quickly on the smaller objects. We again see evidence of terrestrial planet MMRs impeding the infall of the dust.  

Bibliography 

[1] Jones R. L., et al., 2018, Icarus, 303, 181–202

[2] Schunová E., Granvik M., Jedicke R., Gronchi G., Wainscoat R., Abe S., 2012, Icarus, 220, 1050–1063

[3] Fu H., Jedicke R., Durda D. D., Fevig R., Scotti J. V., 2005, Icarus, 178, 434–449

[4] Lasue J., Levasseur-Regourd A.-C., Renard J.-B., 2020, Planetary and Space Science, 190,

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[5] Fixsen D. J., Dwek E., 2002, The Astrophysical Journal, 578, 1009–1014

[6] Rowan-Robinson M., May B., 2013, Monthly Notices of the Royal Astronomical Society,

429, 2894–2902

[7] Marsset M., et al., 2024, Nature, 634, 561–565

[8] Schramm L. S., Brownlee D. E., Wheelock M. M., 1989, Meteoritics, 24, 99–112

[9] Jorgensen J. L., Benn M., Connerney J. E. P., Denver T., Jorgensen P. S., Andersen A. C.,

Bolton S. J., 2021, Journal of Geophysical Research: Planets, 126

[10] Andersson L., et al., 2015, Science, 350

How to cite: Humpage, A.: The dynamics and evolution of simulated near-Earth asteroid families and interplanetary dust, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1560, https://doi.org/10.5194/epsc-dps2025-1560, 2025.

Introduction. The planets also could get similar material due to the ejection of material from their surface when they collided with planetesimals and other bodies. I studied the probabilities p_E, p_V, p_Me, p_Ma, p_Moon, and p_Sun of collisions of bodies ejected from a terrestrial planet with the Earth, Venus, Mercury, Mars, Moon, and the Sun. In each calculation variant, the motion of 250 bodies ejected from a planet was studied at fixed values of the ejection angle i_ej, ejection velocity v_ej, and ejection point. The motion of the ejected bodies was studied during the dynamical lifetime of all bodies, which was usually about a few hundreds Myrs. The gravitational influence of the Sun and all eight planets was taken into account. In different calculation variants, i_ej varied from 15° to 90°, and v_ej varied from the parabolic velocity on the surface of a planet to 20 km/s. Ejection of material was studied from 6 opposite points on the surface of a planet. The probabilities of collisions of bodies ejected from the Earth with the Moon were studied in (Ipatov, 2024a), and the probabilities of collisions of such bodies with planets were studied in (Ipatov, 2025). The probabilities of collisions of bodies ejected from Mars, Mercury, and Venus were briefly discussed in (Ipatov, 2024b,c). Below in this abstracts the probabilities are presented for a whole considered time interval. The fraction of bodies delivered to the Moon in its present orbit was smaller than that delivered to the Earth by a factor of 20-30.

Ejection of bodies from the Earth and the Moon. The fraction of bodies ejected from the Earth and falling back onto the Earth was about 0.2-0.3. At 11.5≤v_ej≤12 km/s, p_V was in the range of 0.22-0.37. The total number of bodies delivered to the Earth and Venus probably did not differ much. The values of p_Me and p_Ma were in the ranges of 0.02-0.08 and 0-0.025, respectively. The probability of a collision of bodies ejected from the Earth with the Moon in its present orbit was about 0.01-0.02 at v_ej=11.3 km/s and 0.005-0.008 at v_ej=16.4 km/s. At v_ej=20 km/s all bodies ejected from the “forward” point on the surface of the Earth or Mars could be ejected into hyperbolic orbits. The probabilities of collisions of ejected bodies with planets were similar for bodies ejected from the Earth and the Moon in its present orbit but for different ejection velocities.

Ejection of bodies from Mars. Some bodies ejected from Mars could collide with the Earth in 0.1 Myr, and some - in hundreds of Myrs. The values of p_E typically did not exceed 0.16. At v_ej≥5.2 km/s, the values of p_V usually exceeded p_E and mainly were less than 0.2. The values of p_Ma were mainly about 0.04-0.25 and 0-0.04 at 5.05≤v_ej≤5.3 and 5.5≤v_ej≤20 km/s, respectively. For the ‘back’ (relative to motion of the planet) point B, p_Ma was usually smaller than for ‘middle’ points (which are on the plane that passes through the Sun and the planet and is perpendicular to the orbital plane). The values of p_Me usually were less than 0.06 and were larger than p_Ma at v_ej≥6 km/s. For ejections from ‘middle’ points, p_Me was mainly about 0.02-0.08 at 5.05≤v_ej≤20 km/s.

Ejection of bodies from Mercury. Most of the bodies ejected from Mercury fell back onto Mercury. The values of p_E usually did not exceed 0.02 and 0.1 at v_ej less than 8 and 15 km/s, respectively. The values of p_V were usually about 0.2-0.3 at 6≤v_ej≤10 km/s. The values of p_V were usually by an order of magnitude greater than p_E. At lower ejection velocities, this difference was greater. For most calculation variants, the fraction of bodies ejected into hyperbolic orbits did not exceed 0.01.

Ejection of bodies from Venus. In this paragraph we discuss the values of the probabilities of collisions with planets for bodies ejected from ‘middle’ points on Venus at 10.4≤v_ej≤16 km/s. In this case, the value of p_Me was about 0.01-0.2, p_V was about 0.3-0.8, and p_E was about 0.04-0.2 (several times less than p_V). At v_ej=16 km/s p_Me was approximately several times larger (from 2 to 10 depending on the ejection point and i_ej) than at v_ej=10.4 km/s. The values of p_V have some tendency (but not for all initial data) to be smaller at higher v_ej. The values of p_Ma often did not exceed 0.01 for all initial data.

For “middle” ejection points at v_ej=20 km/s, p_Me was approximately 0.1-0.15, values of p_V were approximately 0.23-0.35, values of p_E were about 0.04-0.1 at i_ej=45^o, and could be about 0.2 at i_ej=89^o. For the ‘back’ point B, p_Me was about 0.02-0.35 (with a maximum at v_ej=20 km/s), p_V was about 0.4-0.8, p_E was mainly about 0.04-0.2 (but equaled to 0.01 at v_ej=20 km/s and i_ej=89^o). For the ‘forward’ point W at v_ej≤12 km/s, p_Me was about 0.01-0.1, p_V was about 0.3-0.8, and p_E was about 0.1-0.2.

Ejection of dust particles. For ejections of 1-100 micron dust particles from a terrestrial planet, the probability of a collision of a dust particle with the planet usually did not exceed 0.01. The ejected particles mostly fell onto the Sun or were ejected from the Solar System. For micron particles, the ratio between ejected and colliding particles (greater or less than 1) depended on the ejection point and velocity. Most particles with a diameter of about 10-100 microns fell onto the Sun. The dynamical lifetime of most 1-100 micron particles did not exceed 1 Myr.

Acknowledgements: The studies of delivery of material to the Moon or from the Moon were supported by the Russian Science Foundation, project 25-17-00051. Other studies were carried out under government-financed research project for the Vernadsky Institute.

References: Ipatov S.I. (2024a) Solar System Research 58:94-111. https://doi.org/10.1134/S0038094624010040, http://arxiv.org/abs/2405.19797. Ipatov S.I. (2024b) Solar System Research 58. Suppl. 1. P. S50-S63. https://doi.org/10.1134/S0038094623600105, http://arxiv.org/abs/2411.05436. Ipatov S.I. (2024c) Modern astronomy: from the Early Universe to exoplanets and black holes. P. 904-909. https://doi.org/10.26119/VAK2024.143, https://arxiv.org/abs/2501.00134. Ipatov S.I. (2025) Icarus 425, id. 116341 (24 p.). https://doi.org/10.1016/j.icarus.2024.116341, http://arxiv.org/abs/2411.04218.

How to cite: Ipatov, S.: Exchange of ejected material between the terrestrial planets and the Moon, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-11, https://doi.org/10.5194/epsc-dps2025-11, 2025.

Rings are observed around several small bodies of the solar systems: the Centaur Chariklo, the dwarf planet Haumea, the large trans-Neptunian object Quaoar and possibly the active Centaur Chiron. In spite of large differences in sizes and heliocentric distances, these rings share common properties. First, they are dense, in the sense that their dynamics is dominated by collisions, meaning optical depths from a percent or so to essentially opaque. Secondly, they are narrow, thus calling for confining mechanisms. Such features are also observed around the giant planets, with the nine narrow Uranus' rings, the two Adams and Le Verrier rings of Neptune, or the numerous ringlets of Saturn.

Thus, even though their physical parameters and origins are very diverse (Sicardy et al. 2025), these rings show some "convergent evolution", implying that some common mechanisms are at work. Here, we examine the role of spin-orbit resonances (SORs) between the central body and its ring(s), which involve commensurabilities between the rotation rate of a non-asymmetric central body and the mean motion of the ring particles. This non-axisymmetry of the body can take the form of a mass anomaly μ at the surface of the body, or an elongation of the body (or a combination of both). Resonances can also stem from a satellite. However, due to their expected small sizes, there resonance  are expected  to be much weaker than those stemming from SORs.

We have already explored through numerical simulations the fate of a collisional ring orbiting an irregular body, see the dynamical  study  and the numerical  results of Sicardy and Salo (2024) and Salo and Sicardy (2024).

Here, we placed a ring initially close to the second-order 5/7 SOR with Chariklo, meaning that the ring particles complete five revolutions while the central body complete seven rotations. This SOR lies just beyond the synchronous orbit, where the particle mean motion matches the central body spin rate, see Fig.1. The left panel illustrates the main characteristics of the ring evolution: (i) the general outwards migration caused by the positive torque exerted by the mass anomaly and (ii) the temporary capture of the ring in successive first- (aka Lindblad) and second-order SORs 2/3, 3/5, 1/2. The right panel of Fig. 1 shows the same simulation, where the particle dynamical states are plotted in a diagram showing the eccentricities as a function semi-major axis. It illustrates again the temporary capture of the ring in first- and second-order SORs.

In this example, the torque exerted by the mass anomaly eventually pushes the ring outside the SOR. We will examine in the talk the role of a small satellite that may halt this outward migration, in particular at the 1/3 SOR (not visible in Fig. 1). The general view that emerges from this work is that the strong SORs caused by irregularities in the body potential (mass anomaly, elongation or more complex non-axisymmetric features) cause a rapid  confinement of the ring, while a small satellite balances the positive torque from the SOR, thus stabilizing the ring on the long term. This behavior may be generic to rings around small bodies, irrespective to the origin of this material.

Fig. 1 – Left: A density plot showing the evolution of a Chariklo ring with initial optical depth τ₀=0.075, composed of 7,500 inelastically colliding particles with radius 200 m (without self-gravity) orbiting a central body with mass anomaly μ=0.003. The time is expressed in terms of revolutions of the central body and the y-axis show the particle angular momenta L_z, normalized to its value at synchronous orbit. The red curve is the average value of L_z. Right: The green dots show the orbital eccentricities of the particles  shown in Fig. 1 as a function of semi-major axes. The black (resp. red) curves are the theoretical responses of test particles to the corresponding first-order (resp. second-order) SORs.

Acknowledgements  - This work has been supported by the French ANR project Roche, number ANR-23-CE49-0012.

References:
- Salo & Sicardy, "Collisional confinement of 1:3 resonance ringlets around non-spherical bodies",  EPSC Abstracts 17,, EPSC2024-534 (2024), doi: 10.5194/epsc2024-534
- Sicardy & Salo, "The dense resonance meshes around the ringed Chariklo, Haumea and Quaoar", EPSC Abstracts 17, EPSC2024-123 (2024), doi: 10.5194/epsc2024-123
- Sicardy et al., "Origins of rings in the Solar System", Phil. Trans. R. Soc. A 383 (2025): 20240193

How to cite: Sicardy, B. and Salo, H.: The formation of rings around small bodies: an overview, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-111, https://doi.org/10.5194/epsc-dps2025-111, 2025.

Context

The number of spacecrafts investigating small bodies and carrying remote sensing instruments for thermal infrared measurements has been steadily increasing. With the TIRI instrument - a thermal infrared imager - aboard the Hera mission as the latest example [1], there is and will be a wealth of data to interpret using thermophysical models. These models, when combined with mission data, enable the retrieval of key surface characteristics such as thermal conductivity, density, porosity, and grain size. The observation of new small bodies brings new demands on model accuracy, necessitating ongoing improvements to ensure robust, body-specific data analysis. A recent case highlighting this need is the TIR instrument, the predecessor to TIRI, aboard the Hayabusa2 mission. TIR was used to collect thermal maps of the asteroid Ryugu at various stages of the mission, prompting refinements in modelling approaches to match the complexity and specificity of the collected data. Previous findings have shown that a global thermophysical model without surface roughness could not reproduce the thermal measurements from TIR [3, 4]. A combination of a global scale thermophysical model with an adequate surface roughness description was identified as a crucial step toward accurately characterizing Ryugu’s surface thermal environment. Consequently, the next generation of thermophysical models will need to be highly adaptable, enabling the rapid incorporation of new findings and observational data.

Current implementation

We have developed for the purpose of solving the heat transfer equation for dry, airless planetary surfaces. At the core, MoCSI is a one-dimensional finite element method code, which can in principal run on a variety of geometries. In its current form, MoCSI can solve the heat transfer equation on each facet of any given shape model. What sets MoCSI apart from other thermophysical models is its highly modular architecture, which   allows for easy adaptation to different applications and planetary bodies. Key physical properties – such as thermal conductivity, heat capacity, and density are managed by independent modules. This modular structure makes it straightforward to incorporate new or alternative formulations of physical parameters or mechanisms ensuring flexibility and extensibility. Already implemented modules are:

• Physical properties such as density, heat capacity and thermal conductivity, specifically for regolith [5] and porous boulders [6]
• A ray-caster and the solution of the radiosity equations [7]
• Integration of SPICE [8]

These currently available modules allow for a thorough investigation of the thermal surface environment of asteroids.

Verification

Fig. 1: MoCSI solver comparison against the known analytical solution of a semi-infinite domain with constant heat diffusivity and constant incoming heat flux. Temperatures (top panel) and temperature residuals (bottom panel) of MoCSI and the analytical solution are shown as a function of depth.

Fig. 2: Comparison of MoCSI and the ‘’testcrankQ`` case defined for 1DTM [11]. Temperatures (top panel) and temperature residuals (bottom panel) of MoCSI and the Norbert Schörghofer model [9] shown as a function of depth. The minor (agree to the first decimal place) differences are due too different implementations of the surface energy balance upper boundary condition.

Fig 3: Comparison of the radiosity module in MoCSI against the known analytical solution of the surface temperature of a partially shadowed spherical crater presented in [7] with the geometry of [5]. Shown are the temperature residuals between MoCSI and the analytical solution in a top down view onto the crater.

MoCSI’s currently implemented TDMA (Tridiagonal Matrix Algorithm) solver has been verified against known analytical solutions of the heat transfer equation (Figure 1) and against the 1DTM code of Norbert Schörghofer [9] (Figure 2). We use an analytical solution for the radiosity in a spherical crater to verify the implementation of the radiosity equations [10]. As shown in Figure 3, MoCSI’s results closely match the expected values, consistent with findings in [7]. Further results, including applications of MoCSI to selected craters on Ryugu are forthcoming.

References

[1] Okada, T. et al. (2024), LPSC 2024, #1777.

[2] Okada, T. et al. (2020), Nature 579, pp. 518–522.

[3] Shimaki, Y. et al. (2020), Icarus 348, 113835.

[4] Senshu, H. et al. (2022), Int J Thermophys 43, 102.

[5] Gundlach, B. and Blum, J. (2012), Icarus 219, 618.

[6] Maxwell, J.C. (1873), Clarendon Press 2, 3408.

[7] Potter, S.F. et al. (2023), Journal of Computational Physics: X 17, 100130.

[8] Acton, C.H. (1996), Planetary and Space Science 44 No. 1, pp. 65-70.

[9] Schörghofer, N. and Khatiwala, S. (2024), Planet. Sci. J. 5, 120

[10] Ingersoll, A.P. et al. (1992), Icarus 100, pp. 40-47.

[11] Schörghofer, N. (2025), Planetary Code Collection, Github.

How to cite: Schuckart, C., Aussel, B., Rückriemen-Bez, T., Güttler, C., and Gundlach, B.: Modular heat transfer code for dry, airless planetary surfaces: MoCSI, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1426, https://doi.org/10.5194/epsc-dps2025-1426, 2025.

Pluto's small satellites—Styx, Nix, Kerberos, and Hydra—occupy nearly circular orbits that are nearly coplanar with that of Pluto-Charon. While several formation scenarios have been proposed, none has yet provided a fully self-consistent explanation for how these satellites arrived at their present orbits. Early in-situ formation near their current locations—following the Charon-forming impact—is one of the most promising explanations (Woo & Lee 2018), though its dynamical viability depends critically on the free eccentricities of the small satellites.

We adopt the theoretical framework of Lee & Peale (2006) and Woo & Lee (2020), which provides a proper non-Keplerian description of circumbinary orbits and defines free eccentricity as an appropriate generalization of eccentricity for such orbits. Based on this framework, we conduct orbital simulations using the latest ephemerides by Porter & Canup (2023) and Brozović & Jacobson (2024) and apply the fast Fourier transform (FFT) to extract the free eccentricity component of each satellite. To assess the robustness of our results, we also estimate uncertainties in the extracted free eccentricities by repeating the analysis with the uncertainties in the ephemerides reported by Porter & Canup (2023).

We find that the free eccentricities of Nix, Kerberos, and Hydra are consistent with previous values but the free eccentricity of Styx is significantly different. The consistency of the extracted free eccentricities across two independent sets of initial conditions supports the robustness of our results. Based on these dynamical constraints, we then carry out tidal evolution simulations under the in-situ formation scenario to test whether the observed free eccentricities and orbital structure can be reproduced by the early in-situ formation scenario through long-term interactions with the tidally evolving Pluto–Charon binary.

Our results demonstrate that free eccentricity analysis offers a robust way to constrain the formation of Pluto's small satellites. This approach provides a dynamic link between the current orbital structure and the formation and evolution of the system, and may also offer insights into the formation of circumbinary planets in extrasolar systems.

This work is supported in part by Hong Kong RGC grant 17309323.

Figure 1. Free eccentricities of Pluto’s small satellites versus their orbital distances normalized by Pluto’s radius. Black circles with error bars are from Porter & Canup (2023); red triangles are from Brozović & Jacobson (2024). Vertical dashed lines mark the current 3:1 to 6:1 mean-motion commensurabilities with Charon.

How to cite: Jiang, Q. and Lee, M. H.: Dynamical Signatures of Formation and Evolution: Free Eccentricity Analysis of Pluto's Small Satellites, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-282, https://doi.org/10.5194/epsc-dps2025-282, 2025.

Resonances in the main asteroid belt play a significant role in dynamical evolution of small bodies in the Solar system. They are capable of driving objects into near-Earth object (NEO) region as well.

Last year we presented our results for the 5:2 mean motion resonance (MMR) with Jupiter [1, 2]. This work examines the transportation abilities of the 3:1 MMR. The 5:2 MMR is located in the outer part of the main belt and therefore it is believed to be not very efficient in delivering objects to the NEO region [3]. However, it has a non-negligible contribution to NEO population at larger sizes. On the other hand, the 3:1 MMR and the secular resonance  in the inner main belt are considered to be the largest contributors to the steady-state NEO population regardless of the size [4].

We used analogous method as in the case of the 5:2 MMR. Firstly, short-term FLI (fast Lyapunov indicator [5]) maps of the 3:1 MMR were computed in order to distinguish between stable and unstable orbits. Then over 10 000 unstable particles were selected and integrated for a longer period of time, up to 10 Myr, to reveal the transportation abilities of the resonance. All our calculations were made using the MERCURIUS integrator from REBOUND package [6, 7]. We are interested in transportation to the NEO region and final state of these particles. Moreover, we also search for the orbits of potentially hazardous asteroids (PHAs), close encounters with planets and migration closer to the Sun. However, these results might be distorted because we were not taking collisions with planets or the Sun into account, just because we wanted to obtain results comparable to the papers on 5:2 MMR [1, 2, 8]. This means that our test particles survived arbitrarily close encounters. But we actually tracked the close encounters in such a way that we can later tell if there would have been a collision; however, this data is still being processed.

According to our current results, 98.58% of test particles became NEOs at some point during the integration, which is slightly less than in the case of the 5:2 MMR. However, we obtained considerably larger amount of particles reaching a < 1 au (20.71%) and we also registered extremely large number (~ 71.76%) of Sun-grazing particles, i.e. particles that reached perihelion distance q < 0.016 au. In our simulation, the vast majority (96.82%) of test particles entered the Hill sphere of the Earth, which is a little more compared to the 5:2 MMR. The amount of particles that got as close to the orbit of Earth as PHAs was, of course, even larger (97.80%), which is almost the same amount as in the case of the 5:2 MMR. We confronted the results of our simulations with the list of all known PHAs, i.e. we searched for the orbits of PHAs in our simulation. The list was downloaded from JPL SBD (Jet Propulsion Laboratory Small-Body Database) [9]. According to our simulation, the orbits of 49 known PHAs were recovered by at least 70% of the test particles at some point. Orbits of only 7 of these PHAs were also recovered by more than 20% of test particles from simulation dedicated to the 5:2 MMR. The highest percentage was 25.24%. The final distribution of test particles in our simulation revealed that ejections to hyperbolic orbits or to orbits with a > 100 au were predominantly caused by Jupiter, as was expected. We did not find any other value of perihelion distance (other than perihelion distance of Jupiter) that would be significantly associated with elimination of the test particles. The same result we also obtained for 5:2 MMR. The elimination along q ≃ 0.26 au [8] was not confirmed in the case of the 5:2 MMR.

Acknowledgement:

The development and testing of the method, the examination of the 5:2 MMR, as well as participation in EPSC-DPS2025 were supported by the VEGA - Slovak Scientific Grant Agency, grant no. 2/0009/22. The 3:1 MMR examination itself was supported by the PostdokGrant APD0093.

References:

[1] Kováčová M., 2024, A&A, 686, A107

[2] Kováčová M., 2024, Re-examination of the transportation abilities of the 5:2 MMR with Jupiter. In Interactive Conference of Young Scientists 2024. Občianske združenie Preveda, ISBN: 978-80-974608-1-5

[3]Bottke W.F., Morbidelli A., Jedicke R., et al., 2002, Icarus, 156, 399

[4] Granvik M.,  Morbidelli A., Jedicke R., et al., 2018, Icarus, 312, 181.

[5] Skokos C., Gottwald G. & Laskar J., 2016, Chaos detection and predictability (Chapter 2).

[6] Rein H., Hernandez D., Tamayo D., et al., 2019, MNRAS, 485, 5490

[7] REBOUND (https://rebound.readthedocs.io/en/latest/)

[8] Todorović N., 2017, MNRAS, 465, 4441

[9] JPL SBD (https://ssd.jpl.nasa.gov/tools/sbdb_query.html)

How to cite: Kováčová, M.: Examination of the transportation abilities of the 3:1 MMR with Jupiter, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-355, https://doi.org/10.5194/epsc-dps2025-355, 2025.

Collisional sticking of dust is the initial stage of planet formation. Dust is considered to form aggregates, which are composed of many sub-micrometer-sized particles, called dust monomers. The collisions between dust aggregates have been investigated using numerical simulations based on DEM (discrete element method). The DEM simulations calculate the contacting interaction between monomers based on the JKR model, which is an elastic contact model. However, the JKR model does not include the viscosity due to molecular motions. Then, we investigate the contact interaction between monomers, including molecular motions.

We perform molecular dynamics (MD) simulations, which calculate the molecular motions using the intermolecular potential. We use the Lennard-Jones potential as an intermolecular potential and prepare five kinds of monomers with radius of R/σ = 29, 58, 88, 147, and 294, where σ is the intermolecular distance (~0.3 nm); the number of molecules is from 10⁵ to 10⁸. We simulate the head-on collisions between equal-mass monomers with changes in the impact velocity as v_imp/C_s = 6.5×10^-3 - 4.8×10^-2, where C_s is the sound velocity, and analyze the inter-monomer force and the coefficient of restitution (COR). The COR is the ratio of relative velocities between before and after collisions and is a key parameter of the dissipation of monomers’ kinetic energy.

Figure 1 shows the enlarged views of the contact area before and after a collision. After the collision, some molecules move, and the surface becomes rough. The phase when two monomers approach is called “loading”, and the phase when they move away is called “unloading”. Figure 2 shows the inter-monomer force as a function of the distance between the centers of mass of two monomers. At the loading phase, the force obtained in the MD simulations agrees with that of the JKR model. However, the force at the unloading becomes smaller than that at the loading phase. This difference shows the hysteresis of the collisional process, which indicates the energy dissipation. Figure 3 shows the COR as a function of the impact velocity for the collisions between monomers with R/σ = 147. First, we find that the COR of MD simulations is smaller than that of the JKR model. This suggests that collisional kinetic energy is more dissipated in the MD simulations than in the JKR model. The decrease in collisional kinetic energy is converted to the molecular random kinetic energy and potential energy. The change in potential energy means the deformation. Second, we find that the COR has a peak. The decrease in COR appears in only the MD simulations because the feature comes from the significant monomer deformation, which is out of scope of the JKR model. The strong plastic deformation causes large energy dissipation and makes the COR small.

The small COR of the MD simulations suggests dissipative effects caused by molecular motions, which promote the sticking of monomers. The viscosity is not included in DEM simulations. Then, we suggest a new dissipation model, which has a resistance force proportional to the relative velocity between monomers and the contact radius. The dissipation force also depends on the pressure at the center of the contact surface exponentially. We fit the COR of the MD simulations and obtain the appropriate formula. The blue line in Fig. 3 shows the new model, and we can see that the model reproduces the MD simulations well for the low impact velocity. For the high impact velocity, the modeled COR is higher than that of the MD simulations since the model cannot reproduce the energy dissipation due to the strong plastic deformation. The model is a formulation of viscous resistance and cannot represent the physics of deformation.

In this presentation, we show and discuss the above results.

How to cite: Yoshida, Y., Kokubo, E., and Tanaka, H.: Molecular dynamics simulations of dust monomer collisions, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-247, https://doi.org/10.5194/epsc-dps2025-247, 2025.

Asteroids preserve some of the earliest solid materials formed in the Solar System, but their narrow concentration in the asteroid belt belies the wide chemical and isotopic diversity of meteorites, suggesting they were implanted from a broad range of heliocentric distances [1, 2]. Isotopic analyses reveal distinct reservoirs for non-carbonaceous and carbonaceous chondrites, with further divisions among CC types, notably between CM and CI chondrites [3, 4, 5]. Spectroscopic surveys [6, 7, 3] show that large (D > 100 km) CM-like planetesimals display a symmetrical distribution across the asteroid belt, while CI-like asteroids follow a more asymmetric profile [8]. Our previous work [8] demonstrated that this dichotomy reflects two separate implantation events: CM-like bodies likely formed in a pressure bump just outside Jupiter’s early gap [4] and were implanted during Saturn’s growth, while CI-like material formed farther out, beyond the ice giants, and was implanted later during Uranus and Neptune’s migration [9]. This interpretation, consistent with the chondrule-poor nature of CIs, supports a chronology in which asteroids record distinct stages of giant planet formation and migration, providing a key to unlocking the early dynamical evolution of the Solar System. However, the final fate of the remaining population, which was scattered outwards, remains poorly constrained.

Here, we use an orbital model to investigate the injection of planetesimals into the ice-giant formation zone belt following giant planet growth in the protoplanetary disk (PSD) to determine whether CM-like material plausibly became incorporated into the building blocks of Uranus and Neptune (the proto-ice giants) and their satellites, to better constrain the compositional building blocks in the outer Solar System as a whole. We conduct simulations using REBOUND, including 100-km-sized planetesimals evolving under gas drag and the gravitational influence of growing giant planets within various gas disk profiles and planetary configurations, considering two, three, or five planets at a time.

Fig.1:  Final eccentricity and semi-major axis of our remaining particles after 1 Myr of simulation time in the three-planet model, for a moderately sloping gas profile following Σ_g ∝ r^−0.5. While some objects remain at a_i > a_Sat, they are not easily implanted there.

We find that only a small fraction of CM-like bodies can be circularized and implanted beyond Saturn’s orbit, even in gas-rich disks (Fig. 1). Most are either ejected or remain on eccentric orbits, reinforcing the notion that mixing between planetesimal reservoirs was minimal. This supports recent models of the outer Solar System as a series of compositionally distinct, radially confined planetesimal rings [10], potentially separated by gas gaps that further inhibited material exchange.

Our results provide further evidence that CI chondrites originated in a spatially and temporally isolated reservoir, likely the trans-Uranian region, and were implanted much later. As such, the CI-rich asteroids in the main belt may represent the most distant material ever delivered to the inner Solar System, now made accessible by recent sample return missions [11, 12, 13, 14]. These findings position carbonaceous chondrites as a crucial link between the inner and outer Solar System and offer a powerful record of early giant planet dynamics and compositional evolution.

References

[1] A. Morbidelli et al., Chaotic capture of Jupiter’s Trojan asteroids in the early Solar System, 435.7041 (May 2005), pp. 462–465.
[2] Sean N. Raymond and Andre Izidoro, Origin of water in the inner Solar System: Planetesimals scattered inward during Jupiter and Saturn’s rapid gas accretion, 297 (Nov. 2017), pp. 134–148.
[3] Timo Hopp et al., Ryugu’s nucleosynthetic heritage from the outskirts of the Solar System, Science Advances 8.46 (2022), eadd8141.
[4] Jan L. Hellmann et al., Origin of Isotopic Diversity among Carbonaceous Chondrites, 946.2, L34 (Apr. 2023), p. L34.
[5] Fridolin Spitzer et al., The Ni isotopic composition of Ryugu reveals a common accretion region for carbonaceous chondrites, Science Advances 10.39 (2024), eadp2426.
[6] P. Vernazza et al., Compositional Homogeneity of CM Parent Bodies, 152.3, 54 (Sept. 2016), p. 54.
[7] Francesca E. DeMeo et al., Connecting asteroids and meteorites with visible and near-infrared spectroscopy, 380, 114971 (July 2022), p. 114971.
[8] Sarah Anderson, Pierre Vernazza, and Miroslav Brož, Distinct origins for CM and CI-like bodies: Saturn formation region versus
trans-Neptunian disk, European Planetary Science Congress, Sept. 2024, EPSC2024-63, EPSC2024–63.
[9] David Nesvorný et al., Isotopic trichotomy of main belt asteroidsfrom implantation of outer solar system planetesimals, Earth and Planetary Science Letters 626, 118521 (Jan. 2024), p. 118521.
[10] Andre Izidoro et al., Planetesimal rings as the cause of the Solar System’s planetary architecture, Nature Astronomy 6 (Mar. 2022), pp. 357–366.
[11] Toru Yada et al., Preliminary analysis of the Hayabusa2 samples returned from C-type asteroid Ryugu, Nature Astronomy 6 (Dec. 2021), pp. 214–220.
[12] Motoo Ito et al., A pristine record of outer Solar System materials from asteroid Ryugu’s returned sample, Nature Astronomy 6 (Aug. 2022), pp. 1163–1171.
[13] T. Nakamura et al., Formation and evolution of carbonaceous asteroid Ryugu: Direct evidence from returned samples, Science 379.6634, abn8671 (Mar. 2023), abn8671.
[14] Dante S. Lauretta et al., Asteroid (101955) Bennu in the laboratory: Properties of the sample collected by OSIRIS-REx, Meteoritics &
Planetary Science n/a.n/a ().

How to cite: Anderson, S., Vernazza, P., and Broz, M.: Bridging the Gap: How Carbonaceous Chondrites Connect the Inner and Outer Solar System, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-519, https://doi.org/10.5194/epsc-dps2025-519, 2025.

The Laplace facility is an advanced microgravity setup scheduled for launch in fall 2025 and will be installed on the International Space Station (ISS) to explore the initial stages of planet formation. Building upon the insights gained from its predecessor, ICAPS, which was launched aboard the Texus-56 and Texus-58 sounding rockets in 2019 and 2023, Laplace aims to shed light on early dust-agglomeration processes in protoplanetary disks.

Investigating the initial stages of planet formation necessitates the study of many-particle interactions, involving millions of micrometer-sized particles within a low-density gaseous environment (typically a few tens of Pascals), where Knudsen numbers significantly exceed 1. These conditions require extended observation periods, making microgravity environments essential for such experiments. Both ICAPS and Laplace setups are equipped with advanced mechanisms to actively protect the dust cloud from diffusion losses and other external forces, as well as concentrate the particles using an actively-controllable thermophoretic trap, functioning along all three axes.

Concurrently, the dust cloud is accessible to multiple observational instruments. The entire cloud is monitored in three dimensions from two perpendicular overview cameras. Additionally, a dedicated, high-speed long-distance microscope provides non-destructive in-situ analysis of the growing dust aggregates in a central volume of 1 mm² cross-section. An extinction sensor measures light extinction levels throughout the entire cloud. Repeated measurements of individual particle electric charges are performed using controlled DC or AC fields to determine charge distribution and its evolution over time.

This presentation will outline the design and methodologies employed by the Laplace setup, detailing its capabilities, calibration processes, and highlight specific data acquired during the ICAPS flights.

How to cite: von Borstel, I., Blum, J., Schräpler, R., Aktas, C., Balapanov, D., Vedernikov, A., Brisset, J., Molinski, N., and Schubert, B.: The Laplace Experiment: A Facility for Investigating the Initial Stage of Planet Formation, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-497, https://doi.org/10.5194/epsc-dps2025-497, 2025.

A major open question in planetary science and astrophysics is: when exactly does planet formation begin? Within the context of planetary science, it is known that CAIs formed 4.6 Gyr ago, but Kuiper Belt Objects (KBOs) may have formed more than 1 Myr later as radioactive decay of ²⁶Al would have caused melting of the ice that is still present in these bodies. However, in the astrophysical context, there is mounting evidence that planets (and thus planetesimals) should form very rapidly (< 1 Myr; while the protosolar disk is still embedded in its natal envelope).

Here, we present a state-of-the-art 1D model of dust growth in a very young, massive disk that is still embedded in its natal envelope. By simulating a wide range of dynamical processes, including infall from the envelope, magnetically and gravitationally induced turbulence (necessary to produce accretion rates in agreement with observational constraints), and thermal evolution, we find that the dust grain growth is severely limited by turbulent fragmentation at these early stages and at radii less than 20 AU (see Fig 1). Despite this limited grain growth, we are still able to form CAIs at a time remarkably similar to their expected formation in the protosolar nebula.

We conclude with two implications:  First, if planetesimal formation does occur rapidly, the planet-forming disk should be significantly less turbulent. In this case, accretion would need to be driven by a non-turbulent mechanism, such as large-scale magnetically launched winds.  Our future work will address this question. The second possibility is that planetesimal formation may be extremely difficult at these early times due to very limited grain growth. This hypothesis strongly agrees with observations of KBOs suggesting they formed relatively late (> 1Myr after CAIs). Future work should also address this possibility and how to reconcile these implications with observations of planets and their formation environments around other stars that suggest planet formation proceeds rapidly throughout the young disk phase.

Figure 1 - Mid-plane dust-to-gas ratio versus maximum Stokes number (proportional to particle size) at several radial locations in a 1D model) for dust growth in a young, massive, turbulent disk (colored curves near the bottom of the plot).  The curved red line is the regime in which the dust-to-gas ratio and Stokes number are such that streaming instability can readily occur.  The horizontal dotted line (from Carrera et al. 2025) is the minimum dust-to-gas ratio needed for the feedback mechanism from Carrera et al. 2025, in which dust growth and the streaming instability provide a positive feedback route towards planetesimal formation. We find that planetesimal formation is not possible in our model, which either suggests that such young disks are not very turbulent (if planetesimal formation does happen rapidly) or that planetesimal formation takes longer than 1 Myr.  

References:

Carrera, D.; Davenport, Lim, J.; Eriksson, L. E. J.; Lyra, W.; Simon, J. B.; Positive Feedback: How a Synergy Between the Streaming Instability and Dust Coagulation Forms Planetesimals”, submitted to A&A Letters, eprint arXiv:2503.03105.

How to cite: Simon, J., Carrera, D., Davenport, A., Baehr, H., Birnstiel, T., Hall, C., Rea, D., and Stammler, S.: Turbulence Inhibits Early Planetesimal Formation, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-130, https://doi.org/10.5194/epsc-dps2025-130, 2025.

Relict planetesimals in the Kuiper Belt record the earliest epochs of planet formation. In particular, multi-component Kuiper Belt systems are relied upon as primary evidence of planetesimal formation via gravitational collapse. However, two of these systems, (47171) Lempo and (148780) Altjira, are hierarchical triple systems. Unlike a satellite triple system (e.g., Mars, Phobos, and Deimos), hierarchical triple systems lack a dominant central object—instead, they contain an ordered set of relationships (e.g., the Sun, Earth, and the Moon). Ambiguously, Kuiper Belt hierarchical triple systems could either be long-lived systems established during gravitational collapse or more recent creations from collisions or other processes. Here, we show that gravitational collapse can directly create hierarchical triples with dynamical architectures consistent with the observed systems. Using numerical simulations, we demonstrate that angular momentum conservation combined with inefficient orbital energy loss during the gravitational collapse process results in multiple-component systems, some of which are hierarchical triple systems like Lempo and Altjira.

The streaming instability and the subsequent gravitational collapse of self-gravitating pebble clouds have been proposed as an origin for hierarchical triples. Gravitational collapse enables pebbles (~mm-cm-sized objects) to rapidly and efficiently accrete to form large (~10-100 km sized) planetesimals. Crucially, excess angular momentum is imparted onto the pebble clouds via vorticity leftover from the streaming instability such that they are rotating as they collapse. This excess angular momentum is preserved during the collapse, such that pebbles are prevented from accreting into a single central object and instead form binary systems with near-equal-mass components. Numerical models have so far shown that gravitational collapse is a viable mechanism to reproduce the orbits, high rate of binarity (~30%), and physical characteristics of relict planetesimal systems comparable to those within the cold-classical Kuiper Belt. Numerical models have also shown that gravitational collapse can create higher order planetesimal systems (triples, quaternaries, etc.), planetesimals on very tight orbits, and even contact binary planetesimals. However, the creation of hierarchical triples has so far remained elusive due to model limitations and computational constraints.

In order to model the gravitational collapse of a pebble cloud, we used an astrophysical N-body algorithm (PKDGRAV) to calculate the gravitational collapse of a cloud of pebbles in the protoplanetary disk tracking the collapse until accreted planetesimals formed. The original pebble cloud would have contained approximately 10²¹ cm-sized pebbles, which is computationally infeasible, so we were forced to rely on the use of 10⁵ km-sized super-particles. Prior models of gravitational collapse adopted a perfect-merger modeling approach, such that colliding super-particle combine into a new spherical particle and conserve both mass and momentum in the process. However, because the perfect-merging method creates planetesimals as perfect spheres, it cannot adequately record their spin and shape characteristics. Moreover, prior models used inflation factors to increase the super-particle surface areas to resemble the surface areas of a sub-cloud of pebbles and to enhance the super-particle collision rates. Although this is effective at the start of gravitational collapse when innumerable collisions would theoretically occur, it has critical disadvantages. Inflated particles form unrealistically low planetesimal densities (<< 1 g/cm³) and preclude the formation tight binary orbits because mutually orbiting planetesimals inevitably make contact and accrete to form a single spherical planetesimal. However, we avoided the use of inflated particles, which do allow simulation speed-up but prevent the modeling of tight orbits; instead super-particles possess realistic densities (1 g/cm³). We used a soft-sphere discrete element method (SSDEM) to model the contact physics between super-particles. This method models collisions between super-particles with mutual surface penetration that allows them to effectively stick and rest upon one another. Therefore, the SSDEM can create planetesimals as super-particle aggregates with a wide range of shapes and spin states. Furthermore, the SSDEM can track both accretion and decretion from the growing aggregate planetesimals as the collapsing cloud evolves.

With the SSDEM we can effectively create hierarchical triple planetesimal systems from gravitational collapse for the first time (e.g., Figs. 1 and 2). The example hierarchical triple in Figure 1 has mass ratios m₂/m₁ ~ 0.998 and m₃/m₂ ~ 0.963, rotation periods P₁ ~ 27 hours, P₂ ~ 124 hours, and P₃ ~ 9.1 hours, and separations d₁₂ ~ 419 km and d₂₃ ~ 1313 km. The example hierarchical triple in Figure 2 has mass ratios m₂/m₁ ~ 0.643 and m₃/m₂ ~ 0.065, rotation periods P₁ ~ 9.71 hours, P₂ ~ 16.4 hours, and P₃ ~ 19.1 hours, and separations d₁₂ ~ 871 km and d₂₃ ~ 170 km. With our results, we provide evidence that hierarchical triples form directly from gravitational collapse, and they may have been prevalent throughout the early solar system.

Fig. 1: An example of one type of hierarchical triple system created during a simulation of planetesimal formation via gravitational collapse (image dimensions 3,000 km x 3,000 km). This hierarchical triple is composed of an inner tight binary with a small mutual semimajor axis and a third companion planetesimal on a circumbinary orbit with a semimajor axis several times larger than the size of the inner binary orbit.

Fig. 2: An example of another type of hierarchical triple system created during a simulation of planetesimal formation via gravitational collapse (image dimensions 2,000 km x 2,000 km). This hierarchical triple is composed of a tight binary planetesimal system orbiting about a single central planetesimal several times more massive than its companions.

How to cite: Barnes, J., Schwartz, S., and Jacobson, S.: Triple Vision: Hierarchical Triple Planetesimal Systems Created from Gravitational Collapse, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-929, https://doi.org/10.5194/epsc-dps2025-929, 2025.