Driss Takir

Carbon-rich (C-complex) asteroids provide insight into the early solar system, and families of C-complex asteroids serve as robust samples for learning about the internal structure of planetesimals and the materials of the protoplanetary disk. This work investigates the compositions of asteroids within the Polana–Eulalia Complex (PEC) through analyses of JWST NIRSpec spectra , obtained as part of the Spectral Analysis of Main Belt Asteroids in the 3 μ m Region project. NIRSpec observations were conducted for the namesake asteroid of the Eulalia family, (495) Eulalia, as well as three members from the Polana family: (2441) Hibbs, (6712) Hornstein, and (6769) Brokoff. Analyses of the 2.7 μ m region demonstrate that PEC asteroids exhibit absorptions associated with Mg-rich phyllosilicates, in turn underscoring high—though incomplete—degrees of aqueous alteration in the past for both PEC families. Although consistent in regard to composition, (142) Polana and (495) Eulalia show deeper 2.7 μ m bands than the Polana family asteroids, suggesting slight differences in the degrees of aqueous alteration between large and small PEC asteroids. Minor absorptions from 3.0 to 4.0 μ m indicate that (495) Eulalia’s surface may contain more carbonates than (142) Polana, which potentially highlights slight differences between each family’s formation and evolution. Additionally, PEC asteroids also show spectral consistency with Bennu and Ryugu, reinforcing their shared origin in the PEC. Minor absorptions in PEC asteroid spectra also connect to small bodies within and beyond the main belt, providing further evidence of outer solar system formation for the PEC parent bodies.

The NASA OSIRIS-REx mission returned a sample of ~120 grams from the carbonaceous near-Earth asteroid Bennu. Laboratory analyses of the returned sample revealed that it is dark, featuring brighter inclusions and veins, and contains millimeter-sized stones predominantly exhibiting hummocky, mottled, and angular patterns (Lauretta, Connolly, et al. 2024; Connolly, Lauretta, et al. 2025). These laboratory analyses confirmed that Bennu underwent aqueous alteration, akin to other carbonaceous asteroids, such as asteroid Ryugu (Nakamura et al. 2022).As part of a NASA Laboratory Analysis of Returned Samples (LARS) study, we have received a chip of the asteroid Bennu, weighing ~113 mg, from NASA's Johnson Space Center curation (OREX-800084-0). This study aims to evaluate the relationship between organic and carbonate phases and their relationship to aqueous processes on the asteroid's parent body. The Bennu chip was transported and stored in a Teflon bag inside a sealed stainless-steel canister before being opened inside a nitrogen-purged glovebox for spectroscopic analyses. The spectroscopic measurements of the Bennu sample were conducted at the Johns Hopkins University (JHU) Applied Physics Laboratory (APL), where we used a nitrogen-purged glovebox to prevent contamination by terrestrial water while opening the sample container and manipulating the sample (installing it on the sample holder).Figure 1. (Left) Microscope image (0.75X) of the Bennu chip OREX-800084-0. The length of the chip is about 9 mm across. (Right) An image (300x200 µm) of a bright clast in the Bennu sample that was spectrally analysed. Upon opening the canister and unwrapping the Teflon bag in the glovebox, we examined the Bennu chip and found it to have an angular shape (~9 mm x 4 mm x 4 mm) with some bright clasts (~0.5 mm x 1 mm) (Fig. 1, left). Subsequently, we used a nitrogen-purged transfer and measurement container to transport the sample to the APL Geological Near-IR Optimized Microspectroscopic Experiment (GNOME) lab for measurements under nitrogen purge. Reflectance measurements were collected using a Hyperion 2000 FTIR microscope and Invenio-R spectrometer with a spectral field of view of ~100 µm. We collected infrared microscopic (~1.25-28.65 µm) and imaging data from various regions of interest in the Bennu sample (e.g., Fig. 1, right).Figure 2. The spectrum we acquired of a bright clast in the Bennu sample is plotted with spectra of other Bennu samples (Lauretta et al. 2024), OSIRIS-REx OVIRS (Hamilton et al. 2019), and CM and CI carbonaceous chondrites (Takir et al. 2013). Figure 2 presents the measured infrared reflectance spectrum of one of the bright spots shown in Figure 1 (right) from ~ 2 to 4 μm. The longer wavelength data are still being analyzed. The spectrum confirms a narrow absorption band centered at ~ 2.72 μm, which is indicative of Mg-rich serpentine and clay minerals. This absorption feature aligns with those found in CM chondrites, such as LAP 02277, and CI chondrites, like Ivuna. This observation suggests that both Bennu and these meteorites likely experienced similar aqueous alteration environments.Additionally, the spectrum of the bright clast in the Bennu sample displays two prominent doublet absorptions attributed to the planar carbonate CO32- ion (Buijs & Schutte 1961, Hunt, G.R. & Salisbury 1971); these are located at ~ 3.2-3.4 μm (the overtone 2ν3 of the fundamental vibration ν3 at 6.9 μm) and at ~ 3.8-4.0 μm (a combination of ν1 and ν3, where ν1 corresponds to the fundamental vibration at 9 μm and ν3 at 6.9 μm). This carbonate feature is consistent with dolomite, as Figure 3 (upper) illustrates.Organic features due to carbon-hydrogen (C-H) bond stretching typically overlap with one of the carbonate doublets at ~3.4 μm. However, the feature observed in the Bennu sample at ~3.4 μm indicates the presence of pure carbonates with no organics (Fig. 3, lower). In this talk, we will discuss additional spectra of the Bennu sample and their implications for constraining the evolution of carbon reservoirs during secondary processing events (e.g., aqueous alteration) experienced by asteroid Bennu.Figure 3. (Upper) The 3-to-4-μm region of the spectrum of the Bennu sample is compared with those of various carbonaceous phases compiled from the RELAB spectral library. The carbonate feature observed in Bennu is consistent with dolomite and inconsistent with calcite. (Lower) The spectrum of our Bennu sample is plotted alongside the spectra of calcite and coal mixtures (Hancock et al., 2025). Acknowledgements: We would like to acknowledge the support of the NASA LARS grant 80NSSC23K0402. We would also like to thank the OSIRIS-REx mission, including scientists, engineers, and other team members, for their years of dedication to return this sample, as well as the NASA JSC OSIRIS-REx curation team for their work to make the sample available for analysis. References: Buijs, K., and Schutte, C.J.H. 1961, Spectrochimica Acta, vol. 17, pp. 927-932.Connolly Jr., H. C., Lauretta, D. S., et al. 2025, MAPS,1-18.Hancock, A., et al. 2025, LPSC meeting, Abstract #1350.Hunt, G.R. & Salisbury,J.W. 1971) Mod. Geol. 2, 23–30.Lauretta, D. S., Connolly Jr., H. C., et al. 2024, MAPS, 59, Nr 9, 2453–248.Nakamura, T. et al. 2022, Science, 379, Issue 6634.Takir, D. et al. 2013, Meteor. Planet. Sci., 48, 1618.

Primitive asteroids in the Main Belt possess one of the most pristine inventories of materials in the Solar System. Main Belt primitive asteroids are particularly interesting due to clear evidence of phyllosilicates, i.e., silicates that have encountered liquid water and undergone chemical alteration. Since asteroids are thought to be likely contributors to Earth's water content [1-3], mapping hydration across the primitive asteroid population is essential for understanding the compositional structure of the early Solar System and the introduction of water on Earth. Low-albedo (pv < 10%) and low-inclination (i < 10°) primitive asteroid families in the inner Main Belt are dynamically linked to the primitive NEAs Ryugu and Bennu [4,5], further supporting the importance of investigating their composition and the dynamics responsible for their delivery to near-Earth space. The Cycle 3 Program, “Low-Albedo and Inclination Asteroid Families as Tracers for Water and Organics in the Inner Solar System,” is currently conducting observations using the James Webb Space Telescope (JWST) to investigate this category of primitive bodies directly. Utilizing JWST’s NIRSpec Integral Field Unit (IFU), the program is acquiring near-infrared spectra (0.6 – 5.2 µm) from the largest bodies in the Clarissa, Erigone, and Sulamitis asteroid families. Initial investigations into the visible spectra of the Erigone, Sulamitis, and Clarissa families identified a specific trend regarding Fe-rich phyllosilicates: the Erigone and Sulamitis families exhibited similar, high percentages of members showing the 0.7 μm band, indicative of this mineral (60%). In contrast, an extremely low percentage of members expressed the feature in the Clarissa and Polana families [6]. While the absence of a 0.7 μm feature may initially suggest no hydration, it does not provide sufficient grounds to conclude that the body is not hydrated, as Mg-rich phyllosilicates do not show this feature. Studies have shown that although some asteroids lack the 0.7 μm feature, they may still exhibit the 3.0 μm region, whereas all asteroids with a 0.7 μm feature display the 3.0 μm band [7]. This region has been notoriously hard to observe from ground-based observatories due to the Earth’s water-rich atmosphere. JWST observations are required to adequately constrain these bodies' thermal and compositional histories. We will present the compiled preliminary investigations of JWST NIRSpec spectra of (163) Erigone, (302) Clarissa, and (752) Sulamitis. We will search for diagnostic features of hydrated minerals, complex organics, and carbonates. Each spectral feature will be characterized by band center, depth, and area, and compared to features identified in the spectra of carbonaceous chondrite meteorite analogs to investigate possible relationships. Finally, we will explore the compositional diversity of inner belt primitive families and how this connects to their formation and evolutionary history.References: [1] Marty, B. (2012). Earth and Planetary Science Letters. [2] Piani, L. et al. (2020). Science. [3] Mezger, K. et al. (2021). Icarus. [4] Campins, H. et al. (2010). The Astrophysical Journal. [5] Campins, H. et al. (2013). The Astronomical Journal. [6] Morate, D. et al. (2018). Astronomy and Astrophysics. [7] Rivkin, A. et al. (2015). The Astronomical Journal.

The surfaces of airless bodies in our Solar System are continually altered by processes collectively referred to as space weathering (Chapman 2004; Hapke 2001; Pieters & Noble 2016). Space weathering has the potential to complicate remote sensing efforts that aim to understand the composition and evolution of these bodies. In light of recent remote sensing observations and returned sample analysis that show some asteroids are hydrated, we are conducting experiments on lizardite aimed at understanding how the 3-μm region responds to simulated space weathering. Our newly operational ultra-high vacuum (UHV) chamber operates at a base pressure of about 10-9 Torr. We have the capability to heat samples up to ~600 C in order to remove weakly bound terrestrial contaminants, such as H2O, while monitoring the reflectance spectrum of our sample. Currently, we can also irradiate our samples with a pulsed laser, which is used to simulate micrometeorite impacts. As serpentines are a major phase of phyllosilicates found in carbonaceous chondrite meteorites and are therefore expected to be observed on hydrated asteroids, we performed our first weathering experiments using the terrestrial serpentine mineral lizardite. Here we present those results and discuss possible implications in the context on space weathering of airless bodies. CitationsChapman, C. R. 2004, Annu. Rev. Earth Planet. Sci., 32, 539Hapke, B. 2001, Journal of Geophysical Research: Planets, 106, 10039Pieters, C. M., & Noble, S. K. 2016, Journal of Geophysical Research: Planets, 121, 1865

Primitive C-complex asteroids, primarily located in the main asteroid belt, are commonly associated with carbonaceous chondrites (CCs) due to their low geometric albedo (typically pv

Collisional impacts between asteroid-sized objects have been common throughout the history of our solar system and have significantly contributed to the formation of asteroid families (Nesvorný et al., 2015). Of particular interest are the low-albedo (geometric albedo < 0.10) and low-inclination (i ≤ 15°) asteroid families situated within the inner main belt (IMB), between the v6 secular resonance at ~ 2.15 au and the 3:1 mean-motion resonance with Jupiter at ~2.5 au. These families are proposed to be significant sources of carbonaceous near-Earth asteroids (NEAs) such as asteroids Ryugu and Bennu (Bottke et al. 2015; Granvik et al. 2016; Dykhuis and Greenberg, 2015). Carbonaceous NEAs contain abundant water- and carbon-rich materials, which are essential elements for understanding the origin of life on Earth and provide valuable historical records of the early solar system. Exploring the relationships between carbonaceous NEAs and these IMB families also enhances the scientific value of the sample return missions (see this meeting abstract # 678 by Takir et al.). Studying the IMB also has broader implications for the formation of exoplanetary systems, such as PDS 70. The discovery of water vapor by JWST MIRI in the inner part of PDS 70’s protoplanetary disk (Perotti et al. 2023) suggests that water is playing a crucial role in the formation of this young exoplanetary system.As part of the JWST SAMBA3 (Spectral Analysis of Main Belt Asteroids in the 3-µm region) program (Cycle 3 GO; #6384), we are conducting observations of asteroids from seven collisional low-albedo and low-inclination families located in the IMB. The studied families include New Polana, Eulalia, Erigone, Sulamitis, Clarissa, Chaldaea, and Klio. We have selected nine asteroids from these families to investigate potential links with carbonaceous NEAs (see Table 1). Our study focuses on the parent bodies of six asteroid families. For the New Polana family, we are observing three fragments. We will compare these fragments with one another and with the parent body asteroid (142) Polana (Arredondo et al. 2024) to determine whether the fragments from the same family exhibit similar or differing hydration states (e.g., Michel et al. 2020). For our observations, we are utilizing the NIRSpec instrument, which covers a spectral range of~ 0.6 to 5.2 µm. This range includes essential diagnostic absorption features characteristic of primitive and carbonaceous materials, such as H2O/hydroxyl (OH), carbonates, and organics.Table 1. Current JWST observation status of the SAMBA3 program (Cycle 3 GO; #6384).As of this writing, JWST has executed observations for seven asteroids. The observation of asteroid (6769) Brokoff faced an issue and was not fully executed; therefore, it has been rescheduled for the next cycle. Le Pivert-Jolivet et al. (this meeting abstract #359) will discuss the analysis and interpretation of asteroid (84) Klio. Harvison et al. (this meeting abstract #1004) will focus on asteroids (302) Clarissa and (163) Erigone. Additionally, McClure et al. (this meeting abstract #404) will examine asteroids (2441) Hibbs, (6712) Hornstein, and (495) Eulalia. We also expect to observe asteroids (752) Sulamitis and (313) Chladaea before the meeting. Acknowledgements: We would like to acknowledge the support of the Space Telescope Science Institute (JWST-GO-06384.001-A). JdL, TPJ, and JL acknowledge support from the Agencia Estatal de Investigacion del Ministerio de Ciencia e Innovación (AEI-MCINN) under grant "Hydrated Minerals and Organic Compounds in Primitive Asteroids" with reference PID2020-120464GB-100. References: Arredondo, A. et al., 2024. AAS DPS, Abstract##411.02.Bottke, W.F et al., 2015. Icarus 247, 191e217.Dykhuis, M., Greenberg, R., 2015. Icarus 252, 199e211.Granvik, M. et al., 2016. Icarus 312, 181-207.Michel, P. et al., 2020. Nature Communications 11, 2655 (2020.Nesvorný, D. et al., 2015. Asteroids IV 297e321.Perotti, G. et al., 2023 et al. Nature 620, 516-520.

Determining the distribution of water throughout the main asteroid belt can inform us about the formation and evolution of the early Solar System. A powerful method for probing water abundance involves the observation and characterization of carbon-rich (C-complex) asteroids in the “3-μm region,” which contains the fundamental OH stretching mode associated with hydrated or hydroxylated minerals (Rivkin et al. 2002). Carbonaceous chondrites, the meteorite analogs for C-complex primitive asteroids, generally exhibit the OH-strech from Fe- or Mg-rich phyllosilicates, which affect the band shape and center differently (Johnson & Fanale 1973; Takir et al. 2013). The range in band parameters, in turn, aligns with the degree of aqueous alteration (Takir et al. 2013). Though ground-based observations of the 3-μm region are obstructed by Earth’s atmospheric water features, the James Webb Space Telescope (JWST) provides unmatched access to this crucial wavelength range. Additionally, JWST can access features longward of the 3-μm region that could be associated with water-ice, organics, carbonates, or ammoniated phyllosilicates (Campins et al. 2010a; Rivkin & Emery 2010; Clark et al. 2009; Rivkin et al. 2022). Thus, JWST observations of C-complex asteroids in this region allow for insight into the formation and evolution of these bodies and the Solar System at large.The Polana-Eulalia Complex (PEC) is a low-inclination, carbon-rich (C-complex) asteroid population residing in the inner Main Belt (IMB) among numerous other families (Walsh et al. 2013). As shown in Figure 1, the PEC is composed of two dynamically overlapping families centered around (142) Polana and (495) Eulalia, the largest members of each one. The nearby ν6 secular resonance has likely caused some small PEC members to drift into near-Earth space. Notable examples of this dynamical evolution scenario include near-Earth asteroids Bennu and Ryugu, the targets of OSIRIS-REx and Hayabusa2 sample-return spacecraft missions, which are probabilistically traced back to the PEC region (Campins et al., 2010b, 2013; Bottke et al., 2015). Ground-based observational campaigns focused on near-ultraviolet (NUV; 0.35 – 0.46 μm), visible (VIS; 0.46 – 0.9 μm), and near-infrared (NIR; 0.9 – 2.2 μm) wavelengths found that members from both PEC families display featureless spectra (Tatsumi et al. 2022; de León et al. 2016, Pinilla-Alonso et al. 2016). Though PEC asteroids lack 0.7-μm features associated with Fe-bearing phyllosilicates, the presence of the fundamental OH-stretch from Mg-rich phyllosilicates in the 3-μm region cannot be ruled out (Rivkin et al. 2002; Takir et al. 2013). Spectral characterization in this wavelength region is particularly relevant to understanding the distribution of water throughout the Solar System as well as to disentangling the specific family of origin for Bennu and Ryugu.Figure 1: The Yarkovsky Drift of the two families of the PEC, with asteroids Polana (red star) and Eulalia (blue star) at their relatively centralized orbital positions (Vokrouhlický et al. 2006; Walsh et al. 2013).In this work, we present a portion of JWST Cycle 3 spectra from Program #6384, led by Driss Takir. Entitled the “Spectral Analysis of Main Belt Asteroids in the 3-μm Region” (SAMBA3), this JWST program uses the NIRSpec instrument and has acquired spectra from (495) Eulalia and two ~10-km-sized Polana family asteroids: (6712) Hornstein & (2441) Hibbs. Upon calibrating the SAMBA3 spectra, we inspected/calculated spectral parameters for the observed features within and longward of the 3-μm region, including band shape and minimum. In addition to connecting the SAMBA3 spectra with VIS-NIR spectra of these objects, we compare PEC spectra to other relevant spectra, such as the spectrum of Bennu (remote & return-sample), of Ryugu (remote & return), and of (142) Polana (from Cycle 2 – Program #3760, PI A. Arredondo). We also contextualize the PEC spectra with the larger sample from this program, which also observed (84) Klio, (302) Clarissa, and (163) Erigone, largest members of the other carbon-rich, primitive-like families in the IMB. Additionally, we link these PEC asteroid spectra to specific carbonaceous chondrite meteorite types. References:Bottke, W. F., et al. (2015). Icarus, 247.Campins, H., et al. (2010a). Nature, 464.Campins, H., et al. (2010b). Astrophysical Journal Letters, 721.Campins, H., et al. (2013). Astronomical Journal, 146(2).Clark, R. N., et al. (2009). Journal of Geophysical Research: Planets, 114.de León, J., et al. (2016). Icarus, 266.Johnson, T. V. & Fanale, F. P., (1973). Journal of Geophysical Research, 78.Pinilla-Alonso, N., et al (2016). Icarus, 274.Rivkin, A. S., et al. (2002). Asteroids III.Rivkin, A. S., & Emery, J. P., (2010). Nature, Rivkin, A. S., et al. (2022). The Planetary Science Journal, 3, 153.Takir, D., et al. (2013). Meteoritics and Planetary Science, 48(9).Tatsumi, E., et al. (2022). Astronomy and Astrophysics, 664.Vokrouhlický, D., et al. (2006). Icarus, 182(1).Walsh, K. J., et al. (2013). Icarus, 225(1).

Our understanding of solar system evolution is closely tied to interpretations of asteroid composition, particularly the M-class asteroids. These asteroids were initially thought to be the exposed cores of differentiated planetesimals, a hypothesis based on their spectral similarity to iron meteorites. However, recent astronomical observations have revealed hydration on their surface through the detection of 3 μm absorption features associated with OH and potentially H₂O. We present evidence of hydration due mainly to OH on asteroid (16) Psyche, the largest M-class asteroid, using data from the James Webb Space Telescope (JWST) spanning 1.1–6.63 μm. Our observations include two detections of the full 3 μm feature associated with OH and H₂O resembling those found in CY-, CH-, and CB-type carbonaceous chondrites, and no 6 μm feature uniquely associated with H₂O across two observations. We observe 3 μm depths of between 4.3% and 6% across two observations, values consistent with hydrogen abundance estimates on other airless bodies of 250–400 ppm. We place an upper limit of 39 ppm on the water abundance from the standard deviation around the 6 μm feature region. The presence of hydrated minerals suggests a complex history for Psyche. Exogenous sources of OH-bearing minerals could come from hydrated impactors. Endogenous OH-bearing minerals would indicate a composition more similar to E- or P-class asteroids. If the hydration is endogenous, it supports the theory that Psyche originated beyond the snow line and later migrated to the outer main belt.

The asteroid (142) Polana is classified as a B-type asteroid located in the inner Main Belt. This asteroid is the parent of the New Polana family, which has been proposed to be the likely source of primitive near-Earth asteroids such as the B-type asteroid (101955) Bennu. To investigate the compositional correlation between Polana and Bennu at the 3 µm band and their aqueous alteration histories, we analyzed the spectra of Polana in the ~ 2.0–4.0 µm spectral range using the NASA Infrared Telescope Facility in Hawai’i. Our findings indicate that Polana does not exhibit discernable 3 µm hydrated mineral absorption (within 2σ), which is in contrast to asteroid Bennu. Bennu displayed a significant 3 µm absorption feature similar to CM- and CI-type carbonaceous chondrites. This suggests two possibilities: either Bennu did not originate from the New Polana family parented by asteroid Polana or the interior of Bennu’s parent body was not homogenous, with diverse levels of aqueous alteration. Several explanations support the latter possibility, including heating due to shock waves and pressure, which could have caused the current dehydrated state of Bennu’s parent body.

IntroductionLarge and Low-albedo asteroids contain less altered materials that provide information related to the origin and evolution of the solar system and the conditions in which the solar nebula was active. Whether all these large asteroids share the same spectral properties with the dwarf planet Ceres can place crucial constraints on the thermal and dynamical theories of their formation and evolution of the early solar system. To that end, we measured new near-infrared spectra of large and low-albedo asteroids in the outer Main Belt region. Here we will present these new spectra and put the results in the context of dynamical and thermal models, providing more information about the origin and evolution of small bodies of the early solar system.MethodsWe obtained spectra of large asteroids with the long-wavelength cross dispersed (LXD: 1.9-4.2 µm) and PRISM (0.7-2.52 µm) modes of the SpeX spectrograph/imager at the NASA Infrared Telescope Facility (IRTF). The asteroids were observed between 2015 and 2020. The measured LXD spectra of low-albedo asteroids show a steep increase of apparent reflectance longward of ~2.5 μm, due to thermal radiation from the asteroids’ surfaces. Removing the thermal excess in spectra is important for proper characterization of mineral absorptions in asteroids. We used the Near-Earth Asteroid Thermal Model (NEATM) (Harris et al. 1998) to constrain the model thermal flux longward of 2.5 μm in asteroids.ResultsThe studied low-albedo and large asteroids consist of objects with diameters greater than ~120 km, a spectral class of C, B, P, F, and D, and an albedo of less than 9%. All spectra were found to be consistent with Ceres- and Europa-like groups (Figure 1), which were found to have a band centered around 3.05-3.15 µm, a broad 1-µm feature and concave-up NIR (0.85–2.45 µm) spectral shape at shorter wavelengths (Takir and Emery 2012). We also included previously published visible spectra (0.4-0.93-µm) in this study, to help provide a deeper understanding of surface composition of these asteroids.Large and low-albedo asteroids studied previously (Takir and Emery 2012) and here show an interesting orbital distribution in that they are all located in the 2.8 < a < 3.4 AU region (Figure 4). Figure 1 also includes the low albedo asteroids, 24 Themis and 65 Cybele, which were observed by Rivkin and Emery (2010) and Campins et al. (2010), and Licandro et al. (2011), respectively.All large low-albedo asteroids share spectral similarities with Europa- & Ceres-like groups in that they all have a broad 1-µm feature, which is attributed to aqueous alteration; however, these asteroids have an absorption feature centered ~3.15 µm- consistent with Europa-like group only. Hygiea is the only discovered asteroid that has a surface composition similar to that of the dwarf planet (1) Ceres (Takir and Emery 2012, Vernanzza et al. 2017).Figure 1. Orbital distribution of Ceres- and Europa-like groups, which are located in the ~2.8-3.4 AU region. The filled diamonds represent Ceres-like group, which include the dwarf planet Ceres and asteroid Hygiea. The rest of the low-albedo and large asteroids are spectrally similar to the Europa-like group (filled circles).ReferencesCampins et al. Nature 464, 1320–1321(2010). A.W. Harris. Icarus 131, 291-301 (1998). Licandro et al. Astron. Atrophys. 525, A34 (2011). A.S. Rivkin, J.P. Emery, J.P. Nature 64, 1322–1323 (2010). D. Takir, J.P. Emery. Icarus 219, 641-654 (2012). P. Vernazza et al. Astron. J. 153, 72 (2017).