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(2060) Chiron is a large centaur that has been reported active on multiple occasions including during aphelion passage. Studies of Chirons coma during active periods have resulted in the detection of C(triple)N and CO outgassing. Significant work remains to be undertaken to comprehend the activation mechanisms on Chiron and the parent molecules of the gas phases detected. This work reports the study of the ices on Chirons surface and coma and seeks spectral indicators of volatiles associated with the activity. Additionally, we discuss how these detections could be related to the activation mechanism for Chiron and, potentially, other centaurs. In July 2023, the James Webb Space Telescope (JWST) observed Chiron when it was active near its aphelion. We present JWST/NIRSpec spectra from 0.97 to 5.27 microns with a resolving power of 1000, and compare them with laboratory data for identification of the spectral bands. We report the first detections on Chiron of absorption bands of several volatile ices, including CO2, CO, C2H6, C3H8, and C2H2. We also confirm the presence of water ice in its amorphous state. A key discovery arising from these data is the detection of fluorescence emissions of CH4, revealing the presence of a gas coma rich in this hyper-volatile molecule, which we also identify to be in non-local thermal equilibrium (nonLTE). CO2 gas emission is also detected in the fundamental stretching band at 4.27 microns. We argue that the presence of CH4 emission is the first proof of the desorption of CH4 due to a density phase transition of amorphous water ice at low temperature in agreement with the estimated temperature of Chiron during the JWST observations (61 K). Detection of photolytic and proton irradiation products of CH4 and CO2 on the surface, in the coma ice grains, or in the ring material is also detected via a forest of absorption features from 3.5 to 5.3 microns., Comment: 4 figures in paper plus 2 more in the appendix. Accepted as A&A Letter

We observed Sedna, Gonggong, and Quaoar with the NIRSpec instrument on the James Webb Space Telescope (JWST). All three bodies were observed in the low-resolution prism mode at wavelengths spanning 0.7 to 5.2 $\mu$m. Quaoar was also observed at 10x higher spectral resolution from 0.97 to 3.16 $\mu$m using medium-resolution gratings. Sedna's spectrum shows a large number of absorption features due to ethane (C$_2$H$_6$), as well as acetylene (C$_2$H$_2$), ethylene (C$_2$H$_4$), H$_2$O, and possibly minor CO$_2$. Gonggong's spectrum also shows several, but fewer and weaker, ethane features, along with stronger and cleaner H$_2$O features and CO$_2$ complexed with other molecules. Quaoar's prism spectrum shows even fewer and weaker ethane features, the deepest and cleanest H$_2$O features, a feature at 3.2 $\mu$m possibly due to HCN, and CO$_2$ ice. The higher-resolution medium grating spectrum of Quaoar reveals several overtone and combination bands of ethane and methane (CH$_4$). Spectra of all three objects show steep red spectral slopes and strong, broad absorptions between 2.7 and 3.6 $\mu$m indicative of complex organic molecules. The suite of light hydrocarbons and complex organic molecules are interpreted as the products of irradiation of methane. We infer that the differences in apparent abundances of irradiation products are likely due to their distinctive orbits, which lead to different timescales of methane retention and to different charged particle irradiation environments. In all cases, however, the continued presence of light hydrocarbons implies a resupply of methane to the surface. We suggest that these three bodies have undergone internal melting and geochemical evolution similar to the larger dwarf planets and distinct from all smaller KBOs., Comment: 32 pages, 9 figures, 5 tables, accepted for publication in Icarus

James Webb Space Telescope's NIRSpec infrared imaging spectrometer observed the outer solar system dwarf planets Eris and Makemake in reflected sunlight at wavelengths spanning 1 through 5 microns. Both objects have high albedo surfaces that are rich in methane ice, with a texture that permits long optical path lengths through the ice for solar photons. There is evidence for N2 ice absorption around 4.2 um on Eris, though not on Makemake. No CO ice absorption is seen at 4.67 um on either body. For the first time, absorption bands of two heavy isotopologues of methane are observed at 2.615 um (13CH4), 4.33 um (12CH3D), and 4.57 um (12CH3D). These bands enable us to measure D/H ratios of (2.5 +/- 0.5) x 10-4 and (2.9 +/- 0.6) x 10-4, along with 13C/12C ratios of 0.012 +/- 0.002 and 0.010 +/- 0.003 in the surface methane ices of Eris and Makemake, respectively. The measured D/H ratios are much lower than that of presumably primordial methane in comet 67P/Churyumov-Gerasimenko, but they are similar to D/H ratios in water in many comets and larger outer solar system objects. This similarity suggests that the hydrogen atoms in methane on Eris and Makemake originated from water, indicative of geochemical processes in past or even ongoing hot environments in their deep interiors. The 13C/12C ratios are consistent with commonly observed solar system values, suggesting no substantial enrichment in 13C as could happen if the methane currently on their surfaces was the residue of a much larger inventory that had mostly been lost to space. Possible explanations include geologically recent outgassing from the interiors as well as processes that cycle the surface methane inventory to keep the uppermost surfaces refreshed.

The NASA Lucy mission is aimed at the study of the very interesting population of Jupiter Trojans, considered as time capsules from the origin of our solar system. During its journey, the mission will pass near a main belt asteroid, Donaldjohanson. Recently, NASA has announced that a new asteroid in the belt will also be visited by Lucy: 152830 Dinkinesh (1999 VD57). The main goal of this work is to characterise this newly selected target, asteroid Dinkinesh, in order to provide critical information to the mission team. To achieve it, we have obtained visible spectra, colour photometry, and time-series photometry of Dinkinesh, using several telescopes located at different observatories. For the spectra we used the 10.4m Gran Telescopio Canarias (GTC), in the island of La Palma (Spain); for the colour photometry the 4.3m Lowell Discovery Telescope (LDT), near Happy Jack, Arizona (USA) was used; and for the time-series photometry we used the 82cm IAC80 telescope located in the island of Tenerife (Spain). Both visible spectrum and reflectance values computed from colour photometry show that Dinkinesh is an S-type asteroid, i.e., it is composed mainly of silicates and some metal. According to observations done by the NEOWISE survey, S-type asteroids have typical geometric albedo of $p_V$ = 0.223 $\pm$ 0.073. From our time-series photometry, we obtained an asteroid mean magnitude $r'$ = 19.99 $\pm$ 0.05, which provides an absolute magnitude $H_{r'}$ = 17.53 $\pm$ 0.07 assuming $G$ = 0.19 $\pm$ 0.25 for S-types. Using our colour-photometry, we transformed $H_{r'}$ to $H_V$ = 17.48 $\pm$ 0.05. This value of absolute magnitude combined with the geometric albedo provides a mean diameter for Dinkinesh of $\sim$900 m, ranging between a minimum size of 542 m and a maximum size of 1309 m., Comment: 4 pages, 3 figures, Accepted for publication in A&A

Context. Asteroid families are witnesses to the intense collisional evolution that occurred on the asteroid belt. The study of the physical properties of family members can provide important information about the state of differentiation of the parent body and provide insights into how these objects were formed. Several of these asteroid families identified across the main belt are dominated by low-albedo, primitive asteroids. These objects are important for the study of Solar System formation because they were subject to weaker thermophysical processing and provide information about the early conditions of our planetary system. Aims. We aim to study the diversity of physical properties among the Themis, Hygiea, Ursula, Veritas, and Lixiaohua families. Methods. We present new spectroscopic data, combined with a comprehensive analysis using a variety of data available in the literature, such as albedo and rotational properties. Results. Our results show that Themis and Hygiea families, the largest families in the region, present similar levels of hydration. Ursula and Lixiaohua families are redder in comparison to the others and present no sign of hydrated members based on the analysis of visible spectra. Conversely, Veritas presents the highest fraction of hydrated members. Conclusions. This work demonstrates a diverse scenario in terms of the physical properties of primitive outer-belt families, which could be associated with dynamical mixing of asteroid populations and the level of differentiation of the parental body.

Jupiter co-orbital comets have orbits that are not long-term stable. They may experience flybys with Jupiter close enough to trigger tidal disruptions like the one suffered by comet Shoemaker-Levy 9. Our aim was to study the activity and dynamical evolution of the Jupiter co-orbital comet P/2019 LD2 (ATLAS). We present results of an observational study carried out with the 10.4m Gran Telescopio Canarias (GTC) that includes image analyses using a MC dust tail fitting code to characterize its activity, and spectroscopic studies to search for gas emission. We also present N-body simulations to explore its orbital evolution. Images of LD2 obtained on 2020 May 16 show a conspicuous coma and tail. The spectrum does not exhibit any evidence of CN, C2, or C3 emission. The comet brightness in a 2.6 arcsec aperture is r'=19.34+/-0.02 mag, with colors (g'-r')=0.78+/-0.03, (r'-i')=0.31+/-0.03, and (i'-z')=0.26+/-0.03. The temporal dependence of the dust loss rate can be parameterized by a Gaussian having a FWHM of 350 days and a maximum of 60 kg/s reached on 2019 August 15. The total dust loss rate is 1.9e09 kg. LD2 is now following what looks like a short arc of a quasi-satellite cycle that started in 2017 and will end in 2028. On 2063 January 23, it will experience a very close encounter with Jupiter at 0.016 au. Its probability of escaping the solar system during the next 0.5 Myr is 0.53+/-0.03. LD2 is a kilometer-sized object, in the size range of the Jupiter-family comets, with a typical comet-like activity likely linked to sublimation of crystalline water ice and clathrates. Its origin is still an open question. We report a probability of LD2 having been captured from interstellar space during the last 0.5 Myr of 0.49+/-0.02, 0.67+/-0.06 during the last 1 Myr, 0.83+/-0.06 over 3 Myr, and 0.91+/-0.09 during the last 5 Myr., Comment: To be published in Astronomy & Astrophysics. 10 pages, 8 figures

The Arecibo Observatory (AO) is a multidisciplinary research and education facility that is recognized worldwide as a leading facility in astronomy, planetary, and atmospheric and space sciences. AO's cornerstone research instrument was the 305-m William E. Gordon telescope. On December 1, 2020, the 305-m telescope collapsed and was irreparably damaged. In the three weeks following the collapse, AO's scientific and engineering staff and the AO users community initiated extensive discussions on the future of the observatory. The community is in overwhelming agreement that there is a need to build an enhanced, next-generation radar-radio telescope at the AO site. From these discussions, we established the set of science requirements the new facility should enable. These requirements can be summarized briefly as: 5 MW of continuous wave transmitter power at 2 - 6 GHz, 10 MW of peak transmitter power at 430 MHz (also at 220MHz under consideration), zenith angle coverage 0 to 48 deg, frequency coverage 0.2 to 30 GHz and increased Field-of-View. These requirements determine the unique specifications of the proposed new instrument. The telescope design concept we suggest consists of a compact array of fixed dishes on a tiltable, plate-like structure with a collecting area equivalent to a 300m dish. This concept, referred to as the Next Generation Arecibo Telescope (NGAT), meets all of the desired specifications and provides significant new science capabilities to all three research groups at AO. This whitepaper presents a sample of the wide variety of the science that can be achieved with the NGAT, the details of the telescope design concept and the need for the new telescope to be located at the AO site. We also discuss other AO science activities that interlock with the NGAT in the white paper., Comment: 82 pages (executive summary 10 pages), 21 figures, Arecibo observatory white paper (Updated with the complete author list and minor edits)

Using data from the Infrared Array Camera on the Spitzer Space Telescope, we present photometric observations of a sample of 100 trans-Neptunian objects (TNOs) beyond 2.2 {\mu}m. These observations, collected with two broad-band filters centered at 3.6 and 4.5 {\mu}m, were done in order to study the surface composition of TNOs, which are too faint to obtain spectroscopic measurements. With this aim, we have developed a method for the identification of different materials that are found on the surfaces of TNOs. In our sample, we detected objects with colors that are consistent with the presence of small amounts of water and were able to distinguish between surfaces that are predominately composed of complex organics and amorphous silicates. We found that 86% of our sample have characteristics that are consistent with a certain amount of water ice, and the most common composition (73% of the objects) is a mixture of water ice, amorphous silicates, and complex organics. 23% of our sample may include other ices such as carbon monoxide, carbon dioxide, methane or methanol. Additionally, only small objects seem to have surfaces dominated by silicates. This method is a unique tool for the identification of complex organics and to obtain the surface composition of extremely faint objects. Also, this method will be beneficial when using the James Webb Space Telescope for differentiating groups within the trans-Neptunian population., Comment: Accepted for publication in PSJ on October 13, 2020

Makemake is one of the brightest known trans-Neptunian objects, as such, it has been widely observed. Nevertheless, its visible to near-infrared spectrum has not been completely observed in medium resolving power, aimed at studying in detail the absorption features of CH$_4$ ice. In this paper we present the spectrum of Makemake observed with X-Shooter at the Very Large Telescope (Chile). We analyse the detected features, measuring their location and depth. Furthermore, we compare Makemake's spectrum with that of Eris, obtained with the same instrument and similar setup, to conclude that the bands of the CH$_4$ ice in both objects show similar shifts., Comment: 8 pages, 10 figures, accepted in MNRAS

In this work, we present the results of an observational study of 2I/Borisov carried out with the 10.4-m Gran Telescopio Canarias (GTC) and the 3.6-m Telescopio Nazionale Galileo (TNG), both telescopes located at the Roque de Los Muchachos Observatory, in the island of La Palma (Spain). The study includes images in the visible and near-infrared, as well as visible spectra in the 3600 - 9200 A wavelength range. N-body simulations were also performed to explore its orbital evolution and Galactic kinematic context. The comet's dust continuum and near-infrared colours are compatible with those observed for Solar system comets. From its visible spectrum on the nights of 2019, September 24 and 26 we measured CN gas production rates Q(CN) = (2.3 +- 0.4) x 10^{24} mol/s and Q(CN) = (9.5 +- 0.2) x 10^{24} mol/s, respectively, in agreement with measurements reported by other authors on similar nights. We also obtained an upper limit for the C2 production rate of Q(C2) < (4.5 +- 0.1) x 10^{24} mol/s. Dust modelling results indicate a moderate dust production rate of about 50 kg/s at heliocentric distance r_h=2.6 au, with a differential power-law dust size distribution of index -3.4, within the range reported for many comet comae. Our simulations show that the Galactic velocity of 2I/Borisov matches well that of known stars in the solar neighbourhood and also those of more distant regions of the Galactic disc., Comment: 10 pages, 5 figures

Jupiter Trojan asteroids are minor bodies that share Jupiter's orbit around the Sun. Although not yet well understood in origin and composition, they have surface properties that, besides being comparable with other populations of small bodies in the Solar System, hold information that may restrict models of planetary formation. Due their importance, there has been a significant increase in an interest in studying this population. In this context arises the NASA Lucy Mission, with a planned launch of 2021. The Lucy Mission will be the first one to address a group of 6 objects with the aim of investigating, in detail, their nature. In order to provide valuable information for mission planning and maximize the scientific return, we carried out ground based observations of four targets of the mission. Aimed at looking for variabilities on the spectra of (3548) Eurybates, (15094) Polymele and (21900) Orus, we performed rotationally resolved visible spectroscopy of them at SOAR Telescope. We also analyzed the first visible spectrum obtained for the main belt asteroid (52246) Donaldjohanson at Gran Telescopio Canarias. The spectra of Orus and Polymele present rather homogeneous characteristics along the surfaces, and their taxa correspond with those of the two dominant populations in the Trojan population, the P- and the D-type group of objects. Spectroscopy of Eurybates, on the other side, suggests that some variation on the characteristics of the reflectance of this body could be related with its collisional history. Donaldjohanson, the only main belt object in the group of targets, shows, according to our visible spectrum, hints of the presence of hydrated materials. Lucy mission will investigate the surface composition of these targets and will shed light on their connections with other minor bodies populations and in their role on the evolution of the Solar System., Comment: 10 pages, 5 figures

The white paper discusses Arecibo Observatory's plan for facility improvements and activities over the next decade. The facility improvements include: (a) improving the telescope surface, pointing and focusing to achieve superb performance up to ~12.5 GHz; (b) equip the telescope with ultrawide-band feeds; (c) upgrade the instrumentation with a 4 GHz bandwidth high dynamic range digital link and a universal backend and (d) augment the VLBI facility by integrating the 12m telescope for phase referencing. These upgrades to the Arecibo telescope are critical to keep the national facility in the forefront of research in radio astronomy while maintaining its dominance in radar studies of near-Earth asteroids, planets and satellites. In the next decade, the Arecibo telescope will play a synergistic role with the upcoming facilities such as ngVLA, SKA and the now commissioned FAST telescope. Further, the observatory will be actively engaged in mentoring and training programs for students from a diverse background., Comment: Submitted as an Activities and Projects White Paper for the Astro2020 decadal survey (13 pages, 3 figures, 1 table)

NASA's OSIRIS-REx and JAXA's Hayabusa2 sample-return missions are currently on their way to encounter primitive near-Earth asteroids (101955) Bennu and (162173) Ryugu, respectively. Spectral and dynamical evidence indicates that these near-Earth asteroids originated in the inner part of the main belt. There are several primitive collisional families in this region, and both these asteroids are most likely to have originated in the Polana-Eulalia family complex. We present the expected spectral characteristics of both targets based on our studies of our primitive collisional families in the inner belt: Polana-Eulalia, Erigone, Sulamitis, and Clarissa. Observations were obtained in the framework of our PRIMitive Asteroids Spectroscopic Survey (PRIMASS). Our results are especially relevant to the planning and interpretation of in-situ images and spectra to be obtained by the two spacecraft during the encounters with their targets., Comment: 22 pages, 11 figures. Accepted for publication in Icarus on May 11, 2018

Asteroids can be classified into several groups based on their spectral reflectance. Among these groups, the one belonging to the L-class in the taxonomic classification based on visible and near-infrared spectra exhibit several peculiar properties. First, their near-infrared spectrum is characterized by a strong absorption band interpreted as the diagnostic of a high content of the FeO bearing spinel mineral. This mineral is one of the main constituents of Calcium-Aluminum-rich Inclusions (CAI) the oldest mineral compounds found in the solar system. In polarimetry, they possess an uncommonly large value of the inversion angle incompatible with all known asteroid belonging to other taxonomical classes. Asteroids found to possess such a high inversion angle are commonly called Barbarians based on the first asteroid on which this property was first identified, (234)~Barbara. In this paper we present the results of an extensive campaign of polarimetric and spectroscopic observations of L-class objects. We have derived phase-polarization curves for a sample of 7 Barbarians, finding a variety of inversion angles ranging between 25 and 30$^{\circ}$. Spectral reflectance data exhibit variations in terms of spectral slope and absorption features in the near-infrared. We analyzed these data using a Hapke model to obtain some inferences about the relative abundance of CAI and other mineral compounds. By combining spectroscopic and polarimetric results, we find evidence that the polarimetric inversion angle is directly correlated with the presence of CAI, and the peculiar polarimetric properties of Barbarians are primarily a consequence of their anomalous composition., Comment: 31 pages, 21 figures, 5 tables

After the early observations of the disrupted asteroid P/2016 G1 with the 10.4m Gran Telescopio Canarias (GTC), and the modeling of the dust ejecta, we have performed a follow-up observational campaign of this object using the Hubble Space Telescope (HST) during two epochs (June 28 and July 11, 2016). The analysis of these HST images with the same model inputs obtained from the GTC images revealed a good consistency with the predicted evolution from the GTC images, so that the model is applicable to the whole observational period from late April to early July 2016. This result confirms that the resulting dust ejecta was caused by a relatively short-duration event with onset about 350 days before perihelion, and spanning about 30 days (HWHM). For a size distribution of particles with a geometric albedo of 0.15, having radii limits of 1 $\mu$m and 1 cm, and following a power-law with index --3.0, the total dust mass ejected is $\sim$2$\times$10$^7$ kg. As was the case with the GTC observations, no condensations in the images that could be attributed to a nucleus or fragments released after the disruption event were found. However, the higher limiting magnitude reachable with the HST images in comparison with those from GTC allowed us to impose a more stringent upper limit to the observed fragments of $\sim$30 m., Comment: 10 pages, 2 figures Accepted by Astronomical Journal, Nov. 2, 2017

The Cybele and Hilda dynamical groups delimit the outer edge of the asteroid belt. Their compositional distribution is a key element to constrain evolutionary models of the Solar System. In this paper, we present a compositional analysis of these populations using spectroscopic observations, SDSS and NEOWISE data. As part of the PRIMASS (Primitive Asteroids Spectroscopic Survey), we acquired visible spectra of 18 objects in Hilda or Cybele groups with the Goodman High Throughput Spectrometer at the 4.1m SOAR telescope and 20 near-IR spectra of Hilda objects with Near Infrared Camera Spectrograph at the 3.56m TNG. The sample is enlarged with spectra taken from the literature in order to increase our statistical analysis. The spectra were inspected for aqueous alteration bands and other spectral features that can be linked to compositional constraints. The analysis shows a continuous distribution of compositions from the main-belt to the Cybele, Hilda and Trojan regions. We also identify a population in the Trojans group not present in Hilda or Cybele objects., Comment: 26 pages, 10 figures