Keck and Gemini Characterization of Hayabusa2# Rendezvous Target 1998 KY26

Debiased Orbital and Absolute Magnitude Distribution of the Near-Earth Objects

ABSTRACTWe aim to determine the distribution of basaltic asteroids (classified as V-types) based on the spectrophotometric data reported in the MOVIS-C catalogue. A total of 782 asteroids were identified. The observations with all four filters (Y, J, H, Ks), available for 297 of these candidates, allow a reliable comparison with the laboratory data of howardite, eucrite, and diogenite meteorites. We found that the majority of the basaltic candidates (≈95${{\ \rm per\ cent}}$) are located in the inner main belt, while only 29 (≈4${{\ \rm per\ cent}}$) and 8 (≈1${{\ \rm per\ cent}}$) are located in the middle (MMB) and outer main belt (OMB), respectively. A fraction of ≈33${{\ \rm per\ cent}}$ from the V-type candidates is associated with the Vesta family (with respect to AstDyS). We also identified four MMB V-type candidates belonging to (15) Eunomia family, and another four low inclination ones corresponding to (135) Hertha. We report differences between the colour indices and albedo distributions of the V-type candidates located in the inner main belt compared to those from the MMB and OMB. These results support the hypothesis of a different origin for the basaltic asteroids with a semimajor axis beyond 2.5 au. Furthermore, lithological differences are present between the vestoids and the inner low inclination basaltic asteroids. The data allow us to estimate the unbiased distribution of basaltic asteroids across the main asteroid belt. We highlight that at least 80${{\ \rm per\ cent}}$ of the ejected basaltic material from (4) Vesta is missing or is not yet detected because it is fragmented in sizes smaller than 1 km.

From Magnitudes to Diameters: The Albedo Distribution of Near Earth Objects and the Earth Collision Hazard

Spins and shapes of basaltic asteroids and the missing mantle problem

Linking the collisional history of the main asteroid belt to its dynamical excitation and depletion

Main Belt Comets (MBCs) exhibit sublimation-driven activity while occupying asteroid-like orbits in the Main Asteroid Belt. MBCs and candidates show stronger clustering of their longitudes of perihelion around 15° than other objects from the Outer Main Belt (OMB). This potential property of MBCs could facilitate the discovery of new candidates by observing objects in similar orbits. We acquired deep r-band images of 534 targeted asteroids using the Isaac Newton Telescope/Wide Field Camera between 2018 and 2020. Our sample is comprised of OMB objects observed near perihelion, with longitudes of perihelion between 0 and 30° and orbital parameters similar to known MBCs. Our pipeline applied activity detection methods to 319 of these objects to look for tails or comae, and we visually inspected the remaining asteroids. Our activity detection pipeline highlighted a faint antisolar tail-like feature around 2001 NL19 (279870) observed on 2018 November 07, 6 months after perihelion. This is consistent with cometary activity; however, additional observations of this object will be needed during its next perihelion to investigate its potential MBC status. If it is active our survey yields a detection rate of ∼1:300, which is higher than previous similar surveys, supporting the idea of dynamical clustering of MBCs. If not, it is consistent with previously estimated abundance rates of MBCs in the OMB (<1:500).

Transitional disks represent a short stage of the evolution of circumstellar material. Studies of dust grains in these objects can provide pivotal information on the mechanisms of planet formation. Dissimilarities in the spatial distribution of small (micron-size) and large (millimeter-size) dust grains have recently been pointed out. Constraints on the small dust grains can be obtained by imaging the distribution of scattered light at near-infrared wavelengths. We aim at resolving structures in the surface layer of transitional disks (with particular emphasis on the inner 10 - 50 AU), thus increasing the scarce sample of high resolution images of these objects. We obtained VLT/NACO near-IR high-resolution polarimetric differential imaging observations of SAO 206462 (HD135344B). This technique allows one to image the polarized scattered light from the disk without any occulting mask and to reach an inner working angle of 0.1''. A face-on disk is detected in H and Ks bands between 0.1'' and 0.9''. No significant differences are seen between the H and Ks images. In addition to the spiral arms, these new data allow us to resolve for the first time an inner cavity for small dust grains. The cavity size (about 28 AU) is much smaller than what is inferred for large dust grains from (sub)mm observations (39 to 50 AU). The interaction between the disk and potential orbiting companion(s) can explain both the spiral arm structure and the discrepant cavity sizes for small and large dust grains. One planet may be carving out the gas (and, thus, the small grains) at 28 AU, and generating a pressure bump at larger radii (39 AU), which holds back the large grains. We analytically estimate that, in this scenario, a single giant planet (with a mass between 5 and 15 Jupiter masses) at 17 to 20 AU from the star is consistent with the observed cavity sizes.

We present new spectral observations using ground-based telescopes of 23 putative V-type asteroids, selected according to colour surveys in the visible from the Moving Objects Catalogue of the Sloan Digital Sky Survey and near-infrared from the Moving Objects VISTA catalogue. 10 asteroids are orbiting in the middle main belt, while five in the outer part of the main asteroid belt. For the observed asteroids, we assign a taxonomical classification and confirm the basaltic nature for 16 of them. The high-quality spectra in the UV range, obtained with the X-Shooter spectrograph at ESO, allowed the identification of the Fe2+ forbidden transition of pyroxene for 10 asteroids. This band is centred at 506.5 nm, and it is diagnostic of the Ca-content in the pyroxene form. We determined a low Fe-content composition for asteroids (2452) Lyot, (5758) Brunini, (7675) Gorizia, (9197) Endo, (22308) 1990 UO4, (36118) 1999 RE135, (66905) 1999 VC160, and (189597) 2000 WG119, and a composition more rich in Fe for asteroids (75661) 2000 AB79 and (93620) 2000 UQ70. We also present a dynamical investigation of V-type asteroids in the middle and outer main belt. The principal finding of these simulations is that the middle and outer V-types are more likely to be associated with some families, which were considered as possibly originated from the break up of a partially or totally differentiated parent body by diverse studies. This reinforces the hypothesis that the identified V-type in the region were not originated from (4) Vesta and that the number of differentiated objects in the middle and outer main belt must have been much larger than previously assumed.

Jupiter-family comets (JFCs) originate from the Kuiper belt and scattered disk, characterized by short orbital periods and frequent interactions with Jupiter. Their icy composition and a chaotic transition to the inner solar system result in short dynamic and physical lifetimes. These features make JFCs key subjects for understanding the migration of celestial bodies and possibly the delivery of organic materials to the early Earth. Numerous studies of fireballs have historically posited a substantial contribution of large objects from JFC orbits, suggesting a significant presence of cometary material in the near-Earth environment. However, this prevalent belief necessitates a thorough re-examination, as the physical evolution of comets and the mechanisms governing their disintegration remain subjects of debate. Understanding the population of meteoroids and comets is crucial for evaluating this population's physical breakdown and evolution. Current dust models suggest that fragmentation and disintegration of comets play a significant role in populating the zodiacal cloud. However, the larger centimeter-meter scale debris observed by fireball networks has been shown to resemble more asteroidal sources dynamically, indicating that comets might be breaking down directly only into dust-sized fragments. This study extends the scope of existing research by conducting a detailed analysis of both JFCs and comet-like fireball observations, aiming to elucidate the origins and dynamics of objects on JFC-like orbits across varying size scales. Utilizing extensive data from four major fireball networks (DFN, EFN, FRIPON, MORP) and ephemeris data of JFCs, the research comprises 646 fireball orbits and 661 JFCs. Methods include orbital stability analysis over 10,000 years, Lyapunov lifetime estimation, debiased NEO model source region estimation, meteorite fall identification, and meteor shower analysis.The analysis reveals that most meteoroids on JFC-like orbits do not align dynamically with typical JFCs. Instead, they predominantly originate from stable orbits in the outer main asteroid belt, challenging the notion that centimeter-to-meter scale meteoroids on JFC-like orbits primarily derive from JFCs. Furthermore, a subset of 24 JFCs in near-Earth orbits displayed unexpected orbital stability, suggesting a presence of asteroidal interlopers from the outer main belt within the JFC population.Our study demonstrates significant dynamical differences between kilometer-scale JFCs and smaller meteoroids. While the larger JFCs frequently encounter Jupiter and have dynamic, transient orbits, the smaller meteoroids detected by fireball networks originate primarily from stable orbits, indicating a predominant influence of asteroidal material from the outer main belt. This finding challenges conventional assumptions about the origins of JFC-like debris observed on Earth and highlights the complexity and diversity of the small-body environment in our solar system.  

Statistical analysis of the spectral properties of V-type asteroids: A review on what we known and what is still missing

Optical colors of 56 near-Earth objects: trends with size and orbit

The dynamical origins of the dark comets and a proposed evolutionary track

<p>Up to now, only (4) Vesta has been identified as the source of differentiated material, which has been discovered all around the Main Belt region. Most of the basaltic asteroids, identified through spectroscopic measurements, are located in the inner main belt region (2.15-2.5AU) and constitute the Vesta family. These asteroids are indeed dynamically linked to Vesta and share similar spectroscopic properties, showing the absorption bands at 0.92-0.94 micron and 2.0 micron, which are indicative of a basaltic composition. From a dynamical point of view, these objects have proper semimajor axis a<sub>p</sub>, eccentricity e<sub>p</sub> and inclination i<sub>p</sub> in the ranges 2.26 < a<sub>p</sub> < 2.48, 0.075 < e<sub>p</sub> <0.122 and 5.6° < i<sub>p</sub> < 7.9°, respectively (Nesvorny et al. 2015). In addition,  a faint absorption band at 0.506 micron, due to a spin forbidden transition of Fe<sup>2+</sup>, was recently detected also in some V-type asteroids, both members and non-members of the Vesta family (Migliorini et al. 2021).</p> <p>Ground-based observations have shown that few asteroids distributed beyond the 3:1 MMR (Mean Motion Resonance) at 2.5 AU have a basaltic composition (Lazzaro et al. 2000; Hardersen et al. 2004, 2018; Roig et al. 2008; De Sanctis et al. 2011; Solontoi et al. 2012; Ieva et al. 2018; Leith et al. 2017; Migliorini et al. 2018, 2021; Medeiros et al. 2019), although with some differences with respect to Vesta and its family members (Jasmim et al. 2013). Thus, their origin seems to be likely linked to the break-up of large, differentiated objects other than Vesta. Dynamical studies allowed the identification of possible asteroid families, like (221) Eos, (1272) Gefion and (1040) Klumpkea families, which could be the result of the disruption of a differentiated or partly-differentiated parent body. These asteroid families include members with very different spectral types, including basaltic asteroids. Among the asteroids we observed in a previous ground-based campaign, some confirmed V-type asteroids were found to be members of these identified asteroid families, while others lay close to these asteroid families (Migliorini et al. 2021).</p> <p>In the figure below, confirmed basaltic asteroids located beyond 2.5 AU are shown in the proper a- proper I plane and indicated with a circle. Asteroid families are also marked with different colors. Some objects classified as M- (crosses) and A- type (triangles) are also included.</p> <p>We started a new observing campaign to spectrally characterize asteroids selected among the above listed asteroid families, aiming to identify other members with a basaltic composition.</p> <p>In this work we revise the spectral and dynamical properties of basaltic asteroids in the middle and outer main belt, not related to Vesta, and recent observations of asteroids members of the (221) Eos, (1272) Gefion and (1040) Klumpkea families.</p> <p><img src="" alt="" width="402" height="261" /><img src="" alt="" width="404" height="270" /></p> <p>Figure 1. a-i plane of proper semimajor axis and inclination of the middle (left) and outer (right) main belt. Basaltic asteroids from Migliorini et al. (2021) are shown with circles. Some are identified as members of the asteroids families shaped with different colors, while some are locate close to these families. Some M- type and A- type asteroids, located in the same region, are also reported with crosses and triangles, respectively, for comparison.</p> <p> </p> <p> </p> <p>References</p> <p>De Sanctis M.C. et al. 2011, A&A, 533, A77.</p> <p>Hardersen P.S. et al. 2004, Icarus, 159, 178.</p> <p>Hardersen P.S. et al. 2018, AJ, 156, 11.</p> <p>Ieva S. et al. 2018, MNRAS, 479, 2607.</p> <p>Jasmim F.L. et al. 2013, A&A, 552, A85.</p> <p>Lazzaro D. et al. 2000, Science, 288, 2033.</p> <p>Leith T.B. et al. 2017, Icarus, 205, 61.</p> <p>Medeiros H. et al. 2019, MNRAS, 488, 3866.</p> <p>Migliorini A. et al. 2018, MNRAS, 475, 353.</p> <p>Migliorini A. et al. 2021, MNRAS, 504, 2019.</p> <p>Nesvorny D. et al. 2015, Asteroids IV, p. 895.</p> <p>Roig F. et al. 2008, Icarus, 194, 125.</p> <p>Solontoi M. et al. 2012, Icarus, 218, 571.</p> <p> </p>

Preservation of polar ice on near-Earth asteroids originating in the outer main belt: A model study with dynamical trajectories

Aims. The primary objective of this study is to utilize Gaia DR3 asteroid astrometry to detect the Yarkovsky effect, a non-gravitational acceleration that affects the orbits of small asteroids. We then computed the bulk densities for the sample of objects for which we obtained an estimation of the Yarkovsky effect. Methods. We used the version of the OrbFit software that is currently developed at the Minor Planet Center (MPC). We utilized the complete astrometric dataset from the MPC, encompassing all radar data and Gaia DR3 observations. The orbital computation was performed for a total of 446 Near-Earth Asteroids (NEAs; including 93 Potentially Hazardous Asteroids (PHAs)), and 54094 Inner Main Belt Asteroids (IMBAs) as well as Mars Crossing asteroids. Furthermore, we used a new validation method which involved computing the A2 (the Yarkovsky effect) using different observational arcs to observe the stability of the result. We applied the Yarkovsky effect to determine the density of the studied asteroids. Results. Thanks to Gaia DR3 we significantly constrained orbital uncertainties and determined reliable A2 values for 49 Near-Earth Asteroids, including 10 new detections and for all improvements in signal-to-noise ratio. Additionally, we successfully determined the density, along with their uncertainties, for all of these objects. However, regarding IMBAs, although we have made progress, we do not detect Yarkovsky drift for any asteroid in the main belt. Conclusions. Adding a relatively small amount of ultra-precise astrometry from Gaia DR3 to the observations from the Minor Planet Center (MPC) not only significantly improves the orbit of the asteroid but also enhances the detectability of non-gravitational parameters. Utilizing this improved dataset, we were able to determine the densities, along with their uncertainties, for the studied asteroids. Looking ahead, with the upcoming release of Gaia DR4, we anticipate even more detections for NEAs and new detections for IMBA and Mars Crossing Asteroids.