Large mm surveys of star-forming regions enable the study of entire populations of planet-forming disks and reveal correlations between their observable properties. The ever-increasing number of these surveys has led to a flourishing of population study, a valuable tool and approach that is spreading in ever more fields. Population studies of disks have shown that the correlation between disk size and millimeter flux could be explained either through disks with strong substructure, or alternatively by the effects of radial inward drift of growing dust particles.

In this study we performed a population synthesis of the continuum emission of disks varying the initial conditions of the disk and substructure to constrain the parameters and initial conditions of planet-forming disks and address the question of the need for the presence of substructures in disks and, if needed, their predicted characteristics to best reproduce the observed distributions of disk sizes, millimeter fluxes, and spectral indices available.

We showed that observed distributions of spectral indices, sizes, and luminosities together can be best reproduced by disks with significant substructure, namely a perturbation strong enough to be able to trap particles, and that is formed early in the evolution of the disk. Agreement is reached by relatively high initial disk masses and moderate levels of turbulence. Only opacities with high absorption efficiency can reproduce the observed spectral indices. Our results extend to the whole population that substructure is likely ubiquitous, so far assessed only in individual disks and implies that most "smooth" disks hide unresolved substructure.

How to cite: Delussu, L., Birnstiel, T., Miotello, A., Pinilla, P., Rosotti, G., and Andrews, S.: Population Synthesis Models Indicate a Need for Early andUbiquitous Disk Substructures, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-66, https://doi.org/10.5194/epsc2024-66, 2024.

The HD34282 is a protoplanetary disk that hosts an azimuthal asymmetry in the mm dust continuum observed by ALMA. The asymmetry coincides with a one-arm spiral and shadow on the outer disk in near-infrared scattered light, which is coherent with signatures of a vortex shown in simulations. HD34282 thus one of few disks with solid evidence for the presence of a vortex in both NIR and mm observations. The presence of vortices is key to planet formation since they are prime sites to form planetesimals and the potential birthplace of the planets. In our work, we aim to further test the vortex hypothesis for HD34282 by examining two additional theoretical predictions for vortices: i) smaller dust traced at shorter wavelengths is less concentrated azimuthally than larger dust traced at longer wavelengths; ii) dust at the vortex center can reach a maximum dust size of several mm, one order of magnitude or larger than that in the background rings. This is done by carrying out high-resolution multi-wavelength dust continuum observations. We will compare the azimuthal extent of the structure at multiple wavelengths and constrain the dust properties via multi-wavelength spectral energy distribution modelling. Once two predictions are verified, this project will have the potential to provide the most definitive verification of a vortex in a protoplanetary disk and associate the azimuthal asymmetries mm continuum observation with vortices. On the other hand, the negative result would challenge the current theory and motivate alternative explanations for both azimuthal asymmetries in the mm continuum and one-arm spirals in NIR.

How to cite: Ma, X. and Dong, R.: Testing the vortex hypothesis in a protoplanetary disk, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-111, https://doi.org/10.5194/epsc2024-111, 2024.

A major hurdle in planet formation theory is that we do not understand how pebbles congregate into planetesimals. A promising way to overcome this metre-scale barrier involves a mechanism called the streaming instability (SI). This hydrodynamic instability gathers the pebbles into clumps so dense that they collapse gravitationally and form planetesimals.

Unfortunately, the mechanism responsible for the onset of this instability remains mysterious. This makes it hard to evaluate the value of the SI as a planetesimal formation theory: how robust is the mechanism, how does it saturate, etc.

Fortunately, some significant progress has been made recently: J. Squire and P. Hopkins showed that the SI is a Resonant Drag Instability (RDI) involving inertial waves. In the first part of this talk, we build on their insight to produce a clear physical picture of how the SI develops.

Like all RDIs, the SI is built on a feedback loop: in the ‘forward action’, an inertial wave concentrates pebbles into clumps; in the ‘backward reaction’, those drifting pebble clumps excite an inertial wave. Each process breaks into two mechanisms, a fast one and a slow one. At resonance, each forward mechanism can couple with a backward mechanism to close a feedback loop. Unfortunately, the fast-fast loop is stable, so the SI uses the fast-slow and slow-fast loops. Despite this last layer of complexity, we hope that our explanation will help understand how the SI works, in which conditions it can grow, how it manifests itself, and how it saturates.

Another problem is that the SI can only develop in regions containing a high density of similar-sized pebbles. Those conditions are met in large-scale vortices, but no one knows if the SI can feed on vorticial flows. Indeed, each instability can only grow in a few specific flows, and a priori the SI is active in Keplerian flows, not vortex flows. We answer this long-standing question in the second part of the talk.

To do so, we develop a simple pen-and-paper model of a pebble-laden vortex in a protoplanetary disc. We find that if the vortex is weak and anticyclonic, pebbles drift towards its centre. We then build a vortex analog of the shearing box to analyse the local linear stability of our pebble-laden vortex. We find that the pebbles’ drift powers an instability which closely resembles the SI. Indeed, both rely on the same resonance between the pebble drift and inertial waves. This result strengthens the case for vortex-induced planetesimal formation.

How to cite: Magnan, N., Heinemann, T., and Latter, H.: The physical mechanism of the streaming instability, and whether it works in vortices, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-464, https://doi.org/10.5194/epsc2024-464, 2024.

Protoplanetary disks (PPDs), the cradles of planetary systems around young stars, are composed of dust and ice particles immersed in a rarefied gas. These grains possess initial sizes of less than and up to about 1 µm and collide due to Brownian motion, drift motions relative to the gas, and gas turbulence. Provided that the collision velocity remains below a threshold value, grains stick upon first contact and form fractal agglomerates with typical fractal dimensions just below 2. This is the case for collisions caused by Brownian motion, which occur at thermal velocity.

The ICAPS experiment (Interactions in Cosmic and Atmospheric Particle Systems) studies these collisions and growth processes under micogravity conditions. To avoid gravity-induced sedimentation and compaction of the agglomerates, the experiment flew on board of the TEXUS-56 and TEXUS-58 sounding rockets. Monomeric, spherical SiO₂ dust (1.5 µm in diameter) was injected into a vacuum chamber at ~10⁷ times the number density in PPDs, reducing processes that take ~100 years in nature to a few minutes. A specially designed thermal trap was used to stabilize the dust cloud and center it in the fields of view of two perpendicular overview cameras. Further in-situ observations were made with a high-speed camera attached to a long-distance microscope (LDM, see Fig. 1 for example agglomerates). An electrical field was repeatedly applied to measure particle charges that diminish drastically within the first ~20 seconds of experiment time due to neutralizing collisions (see Fig. 2).

Fig. 1: Collage of 190 agglomerates cropped from LDM images (flat-field corrected and inverted).

Fig. 2: Temporal evolution of particle charging of the four experimental runs. The mean charge per monomer is shown in gray and the standard deviation is shown in black. Only the more frequent measurements from the second flight of ICAPS (denoted as SR2) reveal the speed at which the charge is neutralized.

With the high spatial and temporal resolution of the LDM and high-speed camera, it was possible to analyze the Brownian motion and rotation of a great number of particles, yielding their masses, moments of inertia, as well as translational and rotational friction times. From these data, an ensemble fractal dimension of 1.4 could be derived (see Schubert et al. 2023). Careful cross-calibration of the cameras also allowed for mass-frequency distributions of the whole dust cloud to be obtained from the overview cameras, taking into account the cloud morphology. In one out of the four experimental runs, the cloud volume shrank slowly but significantly due to a subtle, thermal anomaly (see Fig. 3), which, combined with a conserved total mass, lead to the runaway growth (or gelation) of a few oligarch agglomerates. These agglomerates clearly detach from the otherwise self-similar mass-frequency distributions (see Schubert et al. 2024 and Fig. 4).

Fig. 3: Shrinking cloud volume across 124 seconds due to a subtle, thermal anomaly in one of the experimental runs (from Schubert et al. 2024).

Fig. 4: Mass-frequency distributions of six consecutive experimental sequences (with subtle thermal anomaly), where N is the number of constituent monomers (from Schubert et al. 2024).

 We modeled the ensemble growth of each of the four experimental runs using a mean-field approximation as well as a Monte-Carlo simulation. The former is based on a version of Smoluchowski's coagulation equation that reads

Here, n, K₀, N, and κ are the number density, a pre-factor, the mean number of monomers, and an exponent, respectively. The exponent is κ ≈ -0.3 for diffusive agglomeration of fractal aggregates in the free molecular flow limit, whereas it becomes κ ≈ 0.5 in the ballistic regime. A formal fit of the solution of the above equation yields κ = 0.236 with the thermal anomaly and κ = 0.350 without, which suggest that the growth is relatively close to the pure ballistic Brownian limit (see Schubert et al. 2024 and Fig. 5).

Fig. 5: Temporal evolution of the frame-wise mean and maximum mass, given as the number of constituent monomers, from the first flight of ICAPS (TEXUS-56), modelled with a mean-field approximation. Data from the first experimental run (thermal anomaly) are denoted in black and those from the second run are shown in gray (from Schubert et al. 2024).

[Schubert et al. 2023] Schubert, B., Molinski, N., Borstel, I., Glißmann, T., Balapanov, D., Vedernikov, A., & Blum, J. (2023). Brownian translation and rotation from the ballistic to the diffusive limit and derivation of the physical properties of dust agglomerates. Phys. Rev. E, 107, 034136. DOI: 10.1103/PhysRevE.107.034136

How to cite: Schubert, B., Blum, J., von Borstel, I., Schräpler, R., Molinski, N., Pöppelwerth, A., Isensee, M., Glißmann, T., Balapanov, D., and Vedernikov, A.: Observation of Dust Particle Collisions and Growth under Microgravity Conditions, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-678, https://doi.org/10.5194/epsc2024-678, 2024.

In a novel experimental setup, we studied the growth of dust aggregates for an extended period of time under realistic protoplanetary conditions, i.e. in a rarefied gas and for relative sedimentation of the grains with velocities on the order of 1 cm/s. We observed a rapid growth of fractal aggregates consisting of µm-sized silica grains and measured their mass spectra as a function of time. Sampling of the aggregates allowed a better characterization of the fractal structure than in-situ observations. We also performed Monte Carlo simulations of the growth process, including explicit collisions, and could achieve a good match to our laboratory observations. Our mean-field model of the growth process is in agreement with the experimental findings and predicts an exponentially fast growth for fractal aggregates (whose collision cross sections are proportional to their mass and whose gas-grain response times are mass-independent), as long as mass loss of the system is negligible. For systems with mass loss, a maximum aggregate mass can be predicted. Our results are directly applicable to the study of dust-aggregate growth in protoplanetary disks, in particular for (but not restricted to) the sedimentation/drift stage before the onset of restructuring. 

How to cite: Blum, J., Aktas, C., Isensee, M., Bodenstein, A., Schubert, B., and Molinski, N.: Exponentially fast growth of dust aggregates during the sedimentation/drift stage, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-7, https://doi.org/10.5194/epsc2024-7, 2024.

In planet formation, the evolution of particles from dust to km-sized planetesimals goes through different stages of growth processes [1]. Starting with micron dust, hit-and-stick collisions create rather fluffy aggregates. With further collisions, these aggregates become more compact until the kinetic energy cannot dissipate into deformation anymore. At about mm-size, the dust aggregates reach the so-called bouncing barrier, where further growth is halted [2]. However, for subsequent growth mechanisms (e.g. hydrodynamic trapping through streaming instability) to set in, cm- to dm-sized pebbles are needed [3]. There are several approaches and explanations how one could overcome the bouncing barrier. One of them is collisional charging. Through tribocharging, there will be a transfer of electric charges between particles with each impact, leaving surface charges at the point of contact [4,5]. In previous experiments, these surface charges have already proven to be the cause of stable cluster formation for solid, monolithic grains [6]. Now, for the very first time, we also observed clustering of charged dust aggregates.

We conducted microgravity experiments at the Drop Tower in Bremen with mm and sub-mm aggregates made from µm dust. The sample is placed in an experiment cell under vacuum conditions. During the 9 seconds of microgravity, the cell can be shaken to distribute the sample and induce inter-particle collisions. The video data show that the particles move rather randomly through the volume of the cell. For the sub-mm aggregates, clusters already form during the shaking phase. For the mm particles, the clustering only begins as soon as the shaking stops and the granular gas has somewhat cooled down. Both samples form cm-sized clusters, the smaller particles more efficiently than the larger ones. The clusters are stable when colliding with the wall but can be eroded by particle impacts at certain velocities. When an electric field is applied to the chamber walls, single particles and small clusters are accelerated to the walls, indicating that they are electrically charged.

Our findings show that electric charges are capable of bridging the bouncing barrier. Sub-mm and mm particles that are made up of µm grains will stick together after impacts below a certain velocity, forming cm-clusters that are mostly stable against further impacts. This paves the way for pebbles to grow to a size range where further growth processes set in, eventually leading to km-sized planetesimals that can accrete more mass gravitationally.

References:

[1]           G. Wurm, J. Teiser, 2021, Nature Reviews Physics, Vol. 3, No. 6, Springer Science and Business Media LLC, p. 405-421

[2]           A. Zsom, C. W. Ormel, C. Güttler, J. Blum, C. P. Dullemond, 2010, Astronomy & Astrophysics, 513, A57

[3]           A. Johansen, H. Klahr, T. Henning, 2006, The Astrophysical Journal, Vol. 636, No. 2, American Astronomical Society, p. 1121-1134

[4]           D. J. Lacks, T. Shinbrot, 2019, Nature Reviews Chemistry, Vol. 3, No. 8, Springer Science and Business Media LLC, p. 465-476

[5]           T. Steinpilz, F. Jungmann, K. Joeris, J. Teiser, G. Wurm, Gerhard, 2020, New Journal of Physics, Vol. 22, No. 9, IOP Publishing, p. 093025

[6]           J. Teiser, M. Kruss, F. Jungmann, G. Wurm, 2021, The Astrophysical Journal, 908, L22

How to cite: Onyeagusi, F. C., Teiser, J., and Wurm, G.: From Dust Till Dawn – How Dust Aggregates grow to Planetesimals with Tribocharging, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-531, https://doi.org/10.5194/epsc2024-531, 2024.

Wind erosion is a serious threat to the evolution of planetesimals in the early stages of planet formation. Since they move around the star at a different orbital velocity than the surrounding gas, they feel a permanent headwind of at least 50 m/s [1]. In the case of eccentric orbits, this difference in velocity can increase significantly. Planetesimals are not solid rocks, but rather a collection of loosely bound dust aggregates [2] that are held together by the low self-gravity. Although the pressure in protoplanetary disks is very low, wind erosion can dismantle planetesimals. As a result, their existence is ruled out in some areas close to the star [3,4].

In a series of wind tunnel experiments in the laboratory and on microgravity platforms such as the drop tower Bremen and parabolic flights, we have recreated the conditions on planetesimals more and more realistically. Under pressures down to 1 Pa and gravity down to 10^-5g, we observed and analysed wind-induced erosion of granular particles. Starting with simple glass spheres, we finally recreated the surface of a pebble pile planetesimal with millimetre sized SiO2 dust aggregates. These aggregates were produced by the collision of micrometre sized SiO2 particles in analogy to the dust growth up to the bouncing barrier in protoplanetary disks.

As a result of our experiments, we found a single formula that predicts the erosion threshold of granular particles on the surface of a planetesimal. Its overall size, the volume and density of the pebbles forming it and its position in the protoplanetary disk can be set as parameters. Together with a suitable disk model, this allows us to define stable and unstable orbits for the evolution of planetesimals into full grown planets.

References

[1]        Weidenschilling S. J., 1977, MNRAS, 180, 57

[2]        Wahlberg Jansson K., Johansen A., Bukhari Syed M., Blum J., 2017, ApJ, 835, 109

[3]        Cedenblad L., Schaffer N., Johansen A., Mehlig B., Mitra D., 2021, ApJ, 921, 123

[4]        Schönau, L., Teiser, J., Demirci, T., Joeris, K., Onyeagusi, F.C., Fritscher, M., Wurm, G., 2023, A&A, 672 A169

How to cite: Schönau, L., Teiser, J., and Wurm, G.: One formula to describe the struggle between planetesimals and gas drag: Insights from microgravity experiments, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-522, https://doi.org/10.5194/epsc2024-522, 2024.

We conducted experiments with ensembles of colliding sub-millimeter basalt particles under prolonged microgravity conditions on a suborbital flight. In these experiments, the sample motion was excited at different levels. Initial shaking of the particles simulates a classical phase of bouncing in early planet formation. During these collisions, the particles charge, as was measured by applying an electric field. Further moderate shaking then leads to the formation of compact clusters of the charged beads, up to several centimeters in size. These clusters grow by individual impacts up to a velocity threshold of about a meter per second. Beyond that velocity, clusters are eroded. We therefore find a shift in barriers from a bouncing particle at millimeters per second to an eroding cluster at meters per second, going along with a shift in particle size from sub-millimeter up to several centimeters. This allows growth well into a size regime that might make clusters prone to hydrodynamic instabilities and subsequent planetesimal formation.

How to cite: Penner, J., Teiser, J., Joeris, K., Onyeagusi, F. C., Kollmer, J., and Wurm, G.: Growing Super Large Sub-Decimeter Pebbles in Protoplanetary Disks: An Erosion Limit for Electrostatic Clustering from Suborbital Experiments, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-911, https://doi.org/10.5194/epsc2024-911, 2024.

Carbonaceous chondrites are some of the most primitive meteorites in our Solar System. They contain refractory inclusions, chondrules, and CI chondrite-like matrix, and originate from planetesimals accreted a few Myr after Solar System formation started. Recent work by Hellmann et al. (2023) showed that there is a fundamental link between the abundances of chondrules and Calcium-Aluminum-rich Inclusions (CAIs), highlighting their abundance is correlated in carbonaceous chondrites. Furthermore, their findings suggest a direct correlation between the abundance of fine-grained dust (i.e., matrix) within carbonaceous chondrites and the accretion time of their parent bodies. They proposed that variations in these abundances reflect the entrapment of CAIs and chondrule precursors within pressure maxima in the protoplanetary disk, likely associated with the gap opened during the formation of Jupiter.

Motivated by these findings, we employ Monte Carlo simulations of dust evolution to explore the plausibility of carbonaceous chondrite parent body formation in the outer regions of a Jupiter-induced gap. Our investigation includes various collision models between refractory inclusions, chondrules and matrix-like materials. At high gas densities, small dust is well-coupled to the gas and can cross the gap, softening the barrier between outer and inner Solar System materials. However, we show that less fragmentation-prone refractory inclusions and chondrules may not leak through the gap. Therefore, their abundance increases in the outer regions (see Figure 1, left panel). As the gas disperses over time, small dust decouples from the gas and gets trapped outside the gap, reducing the previous enrichment of refractory inclusions and chondrules (see Figure 1, right panel). Under favourable conditions for triggering streaming instability, it is possible to reproduce the formation of carbonaceous chondrite parent bodies rich in refractory inclusions and chondrules while their abundance decreases over time.

This scenario constrains current models of Solar System formation, as well as the intricate interactions between different constituents of carbonaceous chondrites and their incorporation into planetesimals. Furthermore, our results could provide valuable benchmarks for future laboratory experiments to elucidate how different materials can stick or fragment during collisions in protoplanetary disks.

Figure 1: Gap-opening by Jupiter at different stages. Blue and black dots indicate matrix-like material and refractory inclusions or chondrules, respectively. Left: at the early stages of the gap-opening, small fragments of matrix-like material leak through the gap, enriching the abundances of refractory inclusions and chondrules in the outer regions of the gap. Right: at later stages, gas density decreases, and matrix loss is reduced. Consequently, the abundance of matrix-like material increases outside the gap.

How to cite: Gurrutxaga, N., Drazkowska, J., and Kleine, T.: Modeling the formation of carbonaceous chondrite parent bodies, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-900, https://doi.org/10.5194/epsc2024-900, 2024.

Abstract

To date, the vast majority of meteorites (≥99%) originate from asteroids in orbits between Mars and Jupiter, yet reaching a consensus on how their diverse chemical, compositional, and isotopic characteristics align with an in-situ formation model within the asteroid belt remains elusive. Recent dynamical models, leveraging measurements from carbonaceous chondrites (CCs), suggest that meteorites may originate from varied heliocentric distances, spanning from the terrestrial planet formation zone to the Kuiper Belt [1, 2, 3]. This broad range is evident in the distribution dichotomies among CCs, especially between CM chondrites (Ch, Cgh-types) and CI chondrites (B, C, Cb, and Cg-types), which collectively account for over 50% of the asteroid belt's mass, excluding Ceres  [4, 5, 6]. These groups show distinctly different spatial distributions (Fig. 1): CM-like bodies display a Gaussian profile, whereas CI-like bodies show an asymmetric distribution, similar to comet-like P-type asteroids [7]. Our study aims to explore the formation and migration history of these asteroid types within the context of giant planet evolution and solar system dynamics to determine whether CM and CI chondrites originated from different locations or at different times.

We use an orbital model initially developed by Ronnet et al. (2018) [8] to investigate the injection of planetesimals into the asteroid belt following giant planet growth in the protoplanetary disk (PSD). We conduct simulations using REBOUND, consisting of 20,000 test particles each, representing 100-km-sized planetesimals. Our five-planet model, inspired by the works of Nesvorný et al. (2015) [9] and Dienno et al. (2017) [10], features Jupiter, Saturn, an additional ice giant (commonly ejected from the solar system), Uranus, and Neptune. Initially, planets are located on low-eccentricity orbits, with Jupiter at 5.4 au and Saturn at the edge of its gap, at 7.3 au. We choose to neglect the influence of the telluric planets, which, having relatively small orbits, require more computation time. We place Neptune in two different configurations: a 'tight' configuration at 16.2 au, in a 3:2, 3:2, 3:2, 3:2 resonance chain, and a 'wide' configuration at 20.3 au, in a 3:2, 3:2, 2:1, 3:2 resonance chain. The test particles' semi-major axes are initialized uniformly between 7 au and 1 au beyond the orbit of Neptune. We examine the effects of gas profile (Σg), planetary growth timescale (τgrowth), and the viscosity parameter (α) on the distribution of planetesimals implanted in the asteroid belt. Notably, we investigate three different gas profiles: the traditional canonical model with a radial dependency of Σg ∝ r−0.5 [11], the Desch et al. 2018 model [12], and the Raymond & Izidoro 2017 model [3].

This study's findings aim to contribute significantly to our understanding of the dynamic processes that shaped the early solar system and the specific pathways that led to the observed dichotomy—or trichotomy—in carbonaceous chondrite composition. By comparing the outcomes of our simulations with existing data, we anticipate providing new insights into the ongoing debate over the formational contexts of these asteroids, thereby enhancing the broader astrophysical models concerning planetary formation and migration.

Figure 1: Distinct spectral classifications (CM, CI/IDP, S) reveal systematic differences in the distributions of main-belt asteroids with D>100 km.

How to cite: Anderson, S., Vernazza, P., and Brož, M.: Distinct origins for CM and CI-like bodies: Saturn formation region versus trans-Neptunian disk, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-63, https://doi.org/10.5194/epsc2024-63, 2024.

There is a general consensus that cometesimals formed in an original reservoir, the primordial Kuiper-belt (PKB), between 20-40 au from the Sun (e.g., review by Nesvorny 2018). From there, they were scattered into the current trans-Neptunian region. In particular, the so-called scattered disk acts as the source reservoir for Jupiter family comets, JFCs (e.g., Duncan & Levison 1997). Yet, the current formation region is primarily constrained by the dynamics that lead to the current day structure of the Kuiper-belt.

Here, we discuss independent constraints coming from noble gas abundances. We combine the data from the two instruments ROSINA (Balsiger et al. 2007; Rubin et al. 2018) and COSIMA (Kissel et al. 2007; Bardyn et al. 2017) onboard ESA's Rosetta mission to derive the bulk elemental composition of comet 67P. These measurements show that Krypton and Xenon are only slightly depleted compared to the solar composition, while Argon is strongly depleted. For comparison, e.g., CI chondrites are heavily depleted in these three noble gases. This suggests that comets formed further out in the protoplanetary disk at a distinctly different distance than the parent bodies of CI meteorites. It also suggests that comets formed between the Xenon and Argon condensation lines. The Krypton line, which lies between the Xenon and Argon lines, is at about 25 au for a passive disk. We will show our latest protoplanetary disk models and their implications on where the respective temperatures occur in the disk in more detail.

How to cite: Marschall, R. and Morbidelli, A.: Constraining the formation region of comets., Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-492, https://doi.org/10.5194/epsc2024-492, 2024.

How does the chemical complexity evolve during the process leading to the formation of a Sun and its planetary system? Is the chemical richness of a Solar-like planetary system at least partially inherited from the earliest stages, or is there a complete chemical reset? A powerful approach to start addressing these questions is by comparing the observed astrochemical content in young protostellar disks with that found in comets—i.e., with the most pristine known material from which our Solar System formed.

The protostellar disk phase is characterized by the blooming of molecular complexity: when the inner regions (~100 au) are heated to temperatures greater than 100 K, dust mantle products thermally sublimate and enrich the chemical composition of the gas (the so-called hot-corino phase).  Additionally, dramatic changes in molecular abundances are expected due to warm gas chemistry. Several lines of evidence suggest that planets could begin forming very early when the protostellar disk is still deeply embedded in a prominent envelope (less than 1 Myr). Consequently, young protostellar disks in the Class 0/I stage serve as the perfect laboratory to study the initial conditions and chemical content of planetesimal formation.

I will present abundance ratios of interstellar complex organic molecules measured in young Class 0/I protostellar disks and compare them with those measured in the 67P/Churyumov–Gerasimenko and other comets. I will emphasize possible evolutionary trends to investigate the inheritance scenario.

How to cite: Bianchi, E.: Tracing our chemical origins: interstellar complex organic molecules from protostellar disks to Solar System comets, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-985, https://doi.org/10.5194/epsc2024-985, 2024.

ExoKuiper belts are a common component of planetary systems that occupy their cold outer regions and whose dust is readily detectable in around 20% of stars. This makes these belts ideal objects to probe those outer regions where planet surveys have struggled to detect all but the most massive exoplanets. The dust in exoKuiper belts is not simply a leftover from protoplanetary discs, it rather is a product of collisions of much larger planetesimals. These belts thus offer a unique window to study the formation and evolution of planetesimal discs as the distribution of dust encodes the planetesimal formation history of these systems.

Over the last 10 years, ALMA dust observations have transformed our understanding of exoKuiper belts by constraining their morphology. This has revealed a great diversity in terms of belt radii and widths. The ongoing ALMA large program ARKS is constraining the detailed structure of these discs for the first time.  In this talk, I will give an overview of the results of this program, with a specific emphasis on the radial structure of these discs. Preliminary results show a wide diversity of substructures, some of which resemble the multi-ring structures in protoplanetary discs. This comparison between the substructures in exoKuiper belts with those in protoplanetary discs can tell us where planetesimal formation is most efficient in protoplanetary discs. 

How to cite: Marino, S.: What does the structure of exoKuiper belts tell us about planetesimal formation?, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-107, https://doi.org/10.5194/epsc2024-107, 2024.

Jupiter-family comets (JFCs) are dynamically-sourced in the scattered Kuiper disk, and are generally less productive than Oort Cloud comets (OCCs). For this reason, JFCs have been underrepresented in ground-based observations of volatiles, such as C₂H₂, C₂H₆, CH₃OH, HCN, H₂O, NH₃, H₂CO, and especially CO and CH₄, for which large Doppler shifts are needed to offset cometary lines from their telluric counterpart absorptions.

The period since 2017 has encompassed some of the best apparitions of JFCs in modern history. These have benefitted from the availability of significantly improved instrumentation for near-IR spectroscopy, and have also coincided with increased synergy between studies of cometary volatiles and model simulations of protoplanetary disk (PPD) chemistry. This presentation will connect findings stemming from near-IR observations of JFCs and OCCs with predictions of PPD midplane ices produced by chemical models for the early solar nebula [Willacy et al. 2022; Astrophysical Journal, 931:164]. Open questions will be discussed in the context of better disentangling natal heritage in cometary volatiles from signatures of post-formative processing, as is needed to understand the comet – early solar system link.

Acknowledgments: Team members gratefully acknowledge support from the following US funding programs: NSF/AAG, NASA/SSO, and NASA/EW. This work benefited from discussions at the International Space Science Institute in Bern during meetings of International Team 361, “From Qualitative to Quantitative: Exploring the Early Solar System by Connecting Comet Composition and Protoplanetary Disk Models.”

How to cite: Bonev, B., Willacy, K., Gibb, E. L., Turner, N., Dello Russo, N., DiSanti, M. A., Vervack, Jr., R. J., Khan, Y., Roth, N. X., Faggi, S., McKay, A. J., Saki, M., Kawakita, H., Villanueva, G. L., and Ejeta, C. T.: Volatiles in Jupiter-family Comets: Synergy Between Infrared Observations and Protoplanetary Disk Chemistry Models, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-1297, https://doi.org/10.5194/epsc2024-1297, 2024.

One of the most promising formation pathways for planetesimals is the concentration of dust via Streaming instability (SI) and the subsequent gravitational collapse into planetesimals. Due to the enhanced dust-to-gas ratio required to trigger the formation via gravitational collapse, the localized formation of a narrow ring of planetesimals is considered in multiple previous studies [3,4]. The subsequent growth of these planetesimals is dominated by mutual collisions up to sizes where they accrete pebbles efficiently. As the timing of core assembly is crucial to the formation of giant planets, understanding the growth of the planetesimals is vital for our understanding of planet formation.

To investigate this scenario, we simulate the formation of the seed of pebble accretion from a filament of planetesimals formed via gravitational collapse. To consistently simulate this early stage of planet formation, we utilize an adapted version of the “Bern model” [1,2]. We track the growth of the largest planetesimal whose initial size is dictated by the initial mass function from Streaming instability simulations [5] from a filament of planetesimals described by a 1D Eulerian disk. Our model newly includes the consideration of multiple important effects that have been neglected or simplified in previous studies: Namely, the viscous spreading of the planetesimals, fragmentation due to the mutual collisions, pebble accretion onto the planetesimals and an improved calculation of the random velocities of the planetesimals which is vital for this stage of planet formation.

In Figure 1. We can see the mass of the largest body in the filament at different times for different locations of the initial planetesimal ring (solid lines). The red dashed line refers to the onset mass of pebble accretion and the blue dashed line to the transition mass [6] above which pebble accretion becomes efficient. The black lines refer to the initial mass of the largest planetesimal (dashed) and the total mass of the ring (dotted). As we can see the growth of the largest body is strongly delayed in the outer disk making it challenging to form the seed of pebble accretion in time to form giant planets. Note that in these simulations we neglected the accretion of pebbles onto the planetesimals and the fragmentation of the planetesimals and are therefore a very conservative estimate for the mass growth of the largest planetesimal.

In conclusion, the formation of a body large enough to accrete pebbles efficiently from a Ring of locally formed planetesimals proves challenging at large separations and is very sensitive to multiple parameters like the stellar mass and the diffusive widening of the filament due to mutual gravitational stirring.

References:

[1] Emsenhuber, A., Mordasini, C., Burn, R., et al. 2021, A&A, 656, A69

[2] Kaufmann, N. & Alibert, Y. 2023, A&A, 676, A46

[3] Lorek, S. & Johansen, A. 2022, A&A, 666, A108

[4] Liu, B., Ormel, C. W., & Johansen, A. 2019, A& A, 624, A114

[5] Schäfer, U., Yang, C.-C., & Johansen, A. 2017, A&A, 59, A69

[6] Ormel, C. W. 2017, in Astrophysics and Space Science Library, ed. M. Pessah & O. Gressel, Vol. 445, 197

How to cite: Kaufmann, N., Alibert, Y., Guilera, O., and Sebastian, I.: Bridging the Gap, From Planetesimals Formation to the Onset of Pebble Accretion: Investigating the Early Growth of Locally Formed Planetesimals, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-997, https://doi.org/10.5194/epsc2024-997, 2024.

Over the last decade, the Atacama Large Millimeter/submillimeter Array (ALMA) made it possible to observe protoplanetary discs, the birth sites of planets, at unprecedented angular resolution and sensitivity, revolutionising our understanding of planet formation. When observed at high-enough angular resolution, protoplanetary discs show sequences of axisymmetric dark and bright substructures, colloquially referred to as “gaps and rings”. The origin of such substructures and the role that they play in the planet formation process are, however, still debated. Substructures are considered to be either the signposts of ongoing interactions between (proto-)planets and their hosting discs, or the ideal location for the formation of new planetary bodies. The best way to solve this “chicken and the egg” problem is characterising the physical properties of these gaps and rings. In this talk, I will first discuss recent attempts to observationally infer the size, density, and temperature of dust in these rings, relying on collecting and modelling multi-frequency, i.e. (sub-)mm to cm, continuum observations in a handful of well studied systems. In particular, I will focus on CI Tau, the only T Tauri star where a candidate hot Jupiter was detected using radial velocity techniques. My high-angular resolution and sensitivity ALMA and VLA continuum observations of this source, reveal that the dust density and size locally increase at the position of the bright rings, suggesting that dust trapping is taking place. I will also show how CI Tau's unique spectral energy distribution allows putting unprecedented constraints on dust composition in this system. Finally, I will introduce a new technique that combines these dust properties with gas kinematics to understand if bright rings might be prone to the formation of planetesimals under streaming instability (SI). In the case of HD 163296, the only source where dust properties and gas kinematics have been well constrained so far, my method reveals that the outermost (100 au) ring shows favourable conditions to trigger the SI.

How to cite: Zagaria, F.: From dust to planets: the ALMA and VLA view of planet formation, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-665, https://doi.org/10.5194/epsc2024-665, 2024.

Exoplanets are often found around Main Sequence stars, but around pre-Main Sequence stars (PMS) it is much harder to find them, and only one confirmed case exists so far. Therefore, it is common to look for indirect signatures of planets in the discs around PMS stars. In this talk, I will discuss detections of variable absorption features of metals in the UV spectra of intermediate-mass PMS stars (the so-called Herbig stars), attributed to (in)falling evaporative bodies (FEBs). These features appear to only be present in flat discs (Meeus group II) , and not in the more flared, gapped discs (Meeus group I) that often are thought to host giant planets, causing large gaps. The absence of signatures of FEBs in the UV spectra could be due to a filtration process at the edge of the gap, halting dust and larger bodies that contain material  with high evaporation temperatures (Si, Fe, Mg,..), while the material with low evaporation temperatures (C,N,O) can flow freely as gas towards the star, where it will be accreted. Such a selective accretion process can cause an underabundance of metals in the photosphere of non-convective stars, what can be verified through spectroscopic metallicity studies, and has indeed already been found in several group I discs around Herbig stars (e.g. Kama et al. 2015, A&A 582, L10; Guzman et al. 2023, A&A  671, 140). 

How to cite: Meeus, G.: Falling Evaporating Bodies in young intermediate mass stars: linked with disc structure?, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-1180, https://doi.org/10.5194/epsc2024-1180, 2024.

Planet formation models are necessary to understand the origins of diverse planetary systems. Circumstellar disc substructures have been proposed as preferred locations of planet formation but a complete formation scenario has not been covered by a single model so far.We aim to study the formation of giant planets facilitated by disc substructure and starting with sub-micron-sized dust. We connect dust coagulation and drift, planetesimal formation, N-body gravity, pebble accretion, planet migration, planetary gas accretion and gap opening in one consistent modelling framework. We find rapid formation of multiple gas giants from the initial disc substructure. The migration trap near the substructure allows the formation of cold gas giants. A new pressure maximum is created at the outer edge of the planetary gap, which triggers the next generation of planet formation resulting in a compact chain of giant planets. A high planet formation efficiency is achieved as the first gas giants are effective in preventing dust from drifting further inwards, which preserves materials for planet formation. Sequential planet formation is a promising framework to explain the formation of chains of gas and ice giants.

How to cite: Lau, T. C. H., Birnstiel, T., Dra̧żkowska, J., and Stammler, S.: Sequential giant planet formation initiated by disc substructure, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-309, https://doi.org/10.5194/epsc2024-309, 2024.

Context. Since the detection of the first known transiting circumbinary planet (CBP), Kepler-16b,
by the Kepler mission, a total pf 14 CBPs have been detected, raising questions about their formation
and dynamical evolution. The current picture of how a planet forms involves a multistage process
consisting of planetary embryo formation, the accretion of pebbles and planetesimals, and finally gas
accretion.
Numerous previous works have investigated the processes involved in planet formation and one way
of performing this analysis is to use hydrodynamic simulations ([6], [3]). This approach has led to a
deeper understanding of the processes that likely lead to the formation of circumbinary planets such
as the Kepler-16, -34 and -35 systems ([8], [2]).
Pebble accretion has been explored also in the formation of planets around single star systems ([4],
[5]). An important consideration is the ability of a planet to open gaps in the dust and gas in the disc
in the vicinity of the planet, depending on the mass of the planet, as presented in [7], for example.
Aims. In this work, we explore how circumbinary planets undergo pebble accretion while embedded
in circumbinary discs close to the vicinity of the central binary system. To calibrate our simulations,
we compare the evolution and results to similar planets accreting in discs around single stars. We aim
to understand the differences that might arise between both formation scenarios and to understand its
consequences for the growth of the planets and the final masses of circumbinary planets versus planets
around single stars.
Methods. In this work we use a modified version of the FARGO3D ([1]) that treats the dust as a
fluid consisting of particles with a given internal density and a fixed size, and includes pebble accretion
onto the planet.
We simulate pebble accretion onto small planets around single and binary star systems with this
multi-fluid routine, using Kepler-16 as a template. The evolution of a low mass core embedded in a
gas disc with a continuous flux of pebbles passing through the system is carefully analyzed.
Results. Pebble accretion efficiency depends mostly on the size of the dust, dust-to-gas ratio, planet
mass and initial orbital location. In our preliminary runs we have observed the opening of gaps in
the dust disc and in the gas disc while the planet’s mass is increasing due to pebble accretion. In our
ongoing simulations, we are evolving both single star and binary systems with an embedded planet.
In line with previous work, we expect the binary systems to form an eccentric inner cavity in their
cicumbinary discs, and this is expected to influence the orbital evolution of the planet and its efficiency
in accreting pebbles compared to planets orbiting a single star.
Conclusions. This work compares a single star with a binary star system in the context of planet
formation and the results are relevant to understanding the different evolutionary paths the same
initial setup can produce because of the presence of the binary. The pebble accretion efficiency will
define which of the scenarios will grow a more massive core, and this will depend on the initial system
parameters. We expect our results to show that compact circumbinary planets will be more massive
than the ones around the single stars, due to the eccentric disc and planet leading to more efficient
pebble accretion.

References
[1] Benı́tez-Llambay, P., and Masset, F. S. Fargo3d: A new gpu-oriented mhd code. The
Astrophysical Journal Supplement Series 223 (2016).
[2] Coleman, G. A., Nelson, R. P., and Triaud, A. H. Dusty circumbinary discs: inner cavity
structures and stopping locations of migrating planets. Monthly Notices of the Royal Astronomical
Society 513 (2022).
[3] Kley, W., and Nelson, R. P. Planet-disk interaction and orbital evolution, 2012.
[4] Lambrechts, M., and Johansen, A. Rapid growth of gas-giant cores by pebble accretion.
Astronomy and Astrophysics 544 (2012).
[5] Lambrechts, M., Johansen, A., and Morbidelli, A. Separating gas-giant and ice-giant
planets by halting pebble accretion. Astronomy and Astrophysics 572 (2014).
[6] Nelson, R. P. On the evolution of giant protoplanets forming in circumbinary discs. Monthly
Notices of the Royal Astronomical Society 345 (2003).
[7] Paardekooper, S. J., and Mellema, G. Planets opening dust gaps in gas disks. Astronomy
and Astrophysics 425 (2004).
[8] Pierens, A., and Nelson, R. P. Migration and gas accretion scenarios for the kepler 16, 34,
and 35 circumbinary planets. Astronomy and Astrophysics 556 (2013).

How to cite: Silva, A. L., Coleman, G., Nelson, R., Winter, O., and Sfair, R.: Multi-fluid hydrodynamical simulations of circumbinary planet formation via pebble accretion, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-635, https://doi.org/10.5194/epsc2024-635, 2024.

Planetary population synthesis is a tool to investigate planet formation by using a simplified global end-to-end planet formation model to create artificial planet populations. This makes it possible to statistically compare model predictions with observations, and to better understand the physical mechanisms of planet formation and their interactions. This project uses the Bern population synthesis model for planetary formation but pushes its boundaries to the earlier stage of planetesimal and embryo formation. 

The model combines the two-population model (Birnstiel et al. 2012) for the solid evolution with a pebble-flux regulated planetesimal formation (Lenz et al. 2019), and then grows planetary embryos from the planetesimals (see Voelkel et al. 2021, paper II). This eliminates the strong assumption of where to place initial planetary embryos in planet formation models. 

Further, we use a modern disk model including an MRI-like alpha transition, weak disk winds (Weder et al. 2023), and thermal torques for planetary migration. Parameters like the planetesimal size and planetesimal fragmentation velocity were varied, and the influence of migration and pebble accretion on the planet evolution were also studied. 

We find a significant under-representation of giant planets, especially cold giants, in all our populations. Only by excluding orbital migration, a sufficient number of cold giant planets could form. Reducing the planetesimal fragmentation velocity or increasing the efficiency of pebble-to-planetesimal conversion all strongly reduce the fraction of giants. These results highlight the added complexity of including a self-consistent planetesimal and embryo formation in global planet formation models.

Figures: Mass-distance evolution of the formed planets in two systems of the nominal population. Violet tracks mean the planet formed early, yellow tracks that it formed late. Horizontal lines mean the planet was ejected from the system. Dotted lines mean the planet was destroyed (ejected, accreted by star, collided with another planet)

References:

Emsenhuber, A., Mordasini, C., Burn, R., Alibert, Y., et al. 2021, A&A 656, A69

Lenz, C.T., Klahr, H. & Birnstiel, L. 2019, ApJ 874 A36

Völkel, O., Deienno, R., Kretke, K., & Klahr, H. 2021, A&A 645, A132 

How to cite: Bauernfeind, A., Burn, R., Voelkel, O., and Klahr, H.: The formation of giant planets in disks with consistent planetesimal and embryo formation, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-1141, https://doi.org/10.5194/epsc2024-1141, 2024.

The outer solar system bodies, including the Galilean moons, are expected to have accreted carbonaceous material during their formation. This carbonaceous material is likely composed of Complex Organic Molecules (COMs), whose formation could have taken place in the protosolar nebula. During their journey through the disk, icy pebbles may have been exposed to different interstellar UV irradiation and temperature conditions, which could have led to the formation of COMs, as experimental studies under similar conditions have demonstrated.

Regarding the formation of the Galilean moons, several scenarios are possible. This study focuses on the formation of the moons in a cold circumplanetary disk, implying that the building blocks originating from the protosolar nebula are not altered by the circumplanetary disk, and their composition is determined solely by the thermodynamic conditions of the protosolar nebula.

The aim of this study is to investigate whether the thermodynamic conditions in the disk were consistent with the formation of COMs in the environment where the Galilean moons formed. To achieve this, the following approach has been taken: 

•  two-dimensional model has been developed to compute the transport of particles within the protosolar nebula using a Lagrangian scheme. This model deduces the accumulated irradiation dose along the particles' paths.
• based on experimental data, the model demonstrates that a small fraction of particles consistently transports COMs within the Jupiter region.

By combining theoretical modeling and experimental data, this study aims to shed light on the potential formation and incorporation of COMs into the Galilean moons during the early stages of the solar system's evolution.

How to cite: Benest Couzinou, T., Amsler Moulanier, A., and Mousis, O.: Investigating the Formation of Complex Organic Molecules in the Protosolar Nebula and Their Incorporation into the Galilean Moons, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-216, https://doi.org/10.5194/epsc2024-216, 2024.

Disc instability remains the leading formation pathway for some of the observed giant planets. In particular, this model can more naturally explain giant planets at large separation, giant planets around M stars, and very young giant planets. However, there are still many open questions regarding this formation mechanism, and the expected population of planets is currently unknown.
We present the results of a new disc instability population synthesis (DIPSY) that addresses many of these questions and makes predictions about the expected population of planets that can be tested observationally.
Our model describes the formation of a star-and-disc system and its evolution until the disappearance of the disc and beyond. It includes a large number of physical effects: gravitational interaction between forming companions, self-consistent gas-accretion, migration and many more.
We find that, while fragmentation (the formation of bound clumps of gas in the disc, a necessary condition for planet formation in the disc instability model) may only happen in a minority of systems, it typically leads to the formation of at least one companion when it does.
The inferred population of companions spans a large range of masses, from the planetary to the stellar regime.
We present and discuss this population, as well as the influence of a number of assumptions.
The figure shows the result of the baseline run: the mass-distance diagram for 100’000 systems after 100 Myr. The final host star mass is given as colour code.

The results of the population synthesis will provide hints both for the theoretical study of planet formation (e.g. hydrodynamic simulations) and future observational surveys of companions.
DIPSY contributes to our understanding of planet formation irrespective of the formation model.

How to cite: Schib, O., Mordasini, C., Helled, R., and Emsenhuber, A.: DIPSY: A New Disc Instability Population Synthesis, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-901, https://doi.org/10.5194/epsc2024-901, 2024.