Solar System Objects Research Articles

A million asteroid observations in the Sloan Digital Sky Survey

Context.The populations of small bodies of the Solar System (asteroids, comets, Kuiper-Belt objects) are used to constrain the origin and evolution of the Solar System. Both their orbital distribution and composition distribution are required to track the dynamical pathway from their regions of formation to their current locations.Aims.We aim at increasing the sample of Solar System objects that have multi-filter photometry and compositional taxonomy.Methods.We search for moving objects in the archive of the Sloan Digital Sky Survey. We attempt at maximizing the number of detections by using loose constraints on the extraction. We then apply a suite of filters to remove false-positive detections (stars or galaxies) and mark out spurious photometry and astrometry.Results.We release a catalog of 1 542 522 entries, consisting of 1 036 322 observations of 379 714 known and unique SSOs together with 506 200 observations of moving sources not linked with any known SSOs. The catalog completeness is estimated to be about 95% and the purity to be above 95% for known SSOs.

Chandrayaan-2 Dual-frequency Synthetic Aperture Radar (DFSAR): Performance Characterization and Initial Results

Abstract The Dual-Frequency synthetic aperture radar (DFSAR) system manifested on the Chandrayaan-2 spacecraft represents a significant step forward in radar exploration of solid solar system objects. It combines SAR at two wavelengths (L and S bands) and multiple resolutions with several polarimetric modes in one lightweight (∼20 kg) package. The resulting data from DFSAR support the calculation of the 2 × 2 complex scattering matrix for each resolution cell, which enables lunar near-surface characterization in terms of radar polarization properties at different wavelengths and incidence angles. In this paper, we report on the calibration and preliminary performance characterization of DFSAR data based on the analysis of a sample set of crater regions on the Moon. Our calibration analysis provided a means to compare on-orbit performance with prelaunch measurements, and the results matched with the prelaunch expected values. Our initial results show that craters in both permanently shadowed regions (PSRs) and non-PSRs that are classified as circular polarization ratio–anomalous in previous S-band radar analyses appear anomalous at the L band also. We also observe that material evolution and physical properties at their interior and proximal ejecta are decoupled. For the Byrgius C crater region, we compare our analysis of dual-frequency radar data with the predicted behaviors of theoretical scattering models. If crater age estimates are available, a comparison of their radar polarization properties at multiple wavelengths similar to that of the three unnamed south polar crater regions shown in this study may provide new insights into how the rockiness of craters evolves with time.

Determination of Rotation Periods for a Large Sample of Asteroids from the K2 Campaign 9

Abstract The Kepler mission is a powerful tool for the study of different types of astrophysical objects or events in the distant universe. However, the spacecraft also provides an opportunity to study solar system objects passing in the telescope’s field of view. The aim of this paper is to determine, for the first time, the rotation periods of a number of asteroids observed by the K2 satellite during the K2 Campaign 9. Using publicly available data from the Kepler mission, we have used the Modified Causal Pixel Model code to perform the aperture-like and point-response function–like photometry of 1026 asteroids. The results allowed us to determine the rotation periods for 188 asteroids. For asteroids with rotation periods that were previously measured, we compared the results and found very good agreement. There are an additional 20 asteroids for which we obtained lower limits on rotation periods and in all cases these limits are at least 100 hr.

Identify low mass volatile organic compounds from cometary ice analogs using gas chromatography coupled to an Orbitrap mass spectrometer associated to electron and chemical ionizations

Analysis of organic matter extracted from meteorites showed that solar system objects present an important molecular diversity. To improve our understanding of such organic matter, new analytical technologies must be developed. The present study displays the first experiments using a GC-FT-Orbitrap-MS to decipher the molecular diversity observed in experiments simulating the evolution of cometary ices. The proposed analytical strategy focuses on the analysis of 110 volatile organic compounds (VOC) with mainly 1 to 6 carbon atoms generated in such cometary ice analogs. Electron ionization (EI) and chemical ionization (CI) modes with methane (CH4) or ammonia (NH3) were optimized and compared. Those developments maximized the intensity of molecular, protonated or deprotonated ions, and improved high-resolution molecular formula unambiguous identification: EI mode is too energetic to provides there detection, while it is not the case in CI mode. Particularly, NH3 as a reagent gas improves amine identification in positive mode (PCI), and esters, alcohols, carbonyls, amides, carboxylic acids and nitriles in negative mode (NCI). The combination of both EI and CI mass spectrum analysis improves molecular identification, thanks to the detection of molecular, deprotonated or protonated ion of highest intensity and fragment formula assignments. The EI and NCI NH3 combination allows formula assignments up to 94% of our database with limit of detection up to 7 ppm. This procedure has been validated for untargeted GC-FT-Orbitrap-MS analysis of VOC coming from the processing of cometary ice analogs.

Somangnet: Small Telescope Network of Korea

Even in an era where 8-meter class telescopes are common, small telescopes are considered very valuable research facilities since they are available for rapid follow-up or long term monitoring observations. To maximize the usefulness of small telescopes in Korea, we established the SomangNet, a network of 0.4-1.0 m class optical telescopes operated by Korean institutions, in 2020. Here, we give an overview of the project, describing the current participating telescopes, its scientific scope and operation mode, and the prospects for future activities. SomangNet currently includes 10 telescopes that are located in Australia, USA, and Chile as well as in Korea. The operation of many of these telescopes currently relies on operators, and we plan to upgrade them for remote or robotic operation. The latest SomangNet science projects include monitoring and follow-up observational studies of galaxies, supernovae, active galactic nuclei, symbiotic stars, solar system objects, neutrino/gravitational-wave sources, and exoplanets.

Hydration of Nebular Minerals through the Implantation–Diffusion Process

Abstract Recent studies have detected structurally bound water in the refractory silicate minerals present in ordinary and enstatite chondrite meteorites. The mechanism for the incorporation of the hydrogen is not well defined. In this paper we quantitatively examine a two-fold process involving the implantation and diffusion of nebular hydrogen ions that is responsible for the hydration of the chondritic minerals. Our simulations show that depending on critical parameters, including the flux of the protons in nebular plasma, retention coefficient, temperature of the silicate minerals, and desorption rate of implanted hydrogen, the implantation of low-energy hydrogen ions can result in equivalent water contents of ∼0.1 wt% in chondritic silicates within 10 years. Thus, this novel mechanism operating in the nebula at 10−3 bar pressure and <650 K temperatures can efficiently hydrate the free-floating chondritic minerals prior to the rapid formation of planetesimals inside the snow line, and agree well with the wet accretion scenario for the inner solar system objects.

Fast period searches using the Lomb–Scargle algorithm on Graphics Processing Units for large datasets and real-time applications

Computing the periods of variable objects is well-known to be computationally expensive. Modern astronomical catalogs contain a significant number of observed objects. Therefore, even if the period ranges for particular classes of objects are well-constrained due to expected physical properties, periods must be derived for a tremendous number of objects. In this paper, we propose a GPU-accelerated Lomb–Scargle period finding algorithm that computes periods for single objects or for batches of objects as is necessary in many data processing pipelines. We demonstrate the performance of several optimizations, including comparing the use of shared and global memory GPU kernels and using multiple CUDA streams to copy periodogram data from the GPU to the host. Also, we quantify the difference between 32-bit and 64-bit floating point precision on two classes of GPUs, and show that the performance degradation of using 64-bit over 32-bit is greater on the CPU than a GPU designed for scientific computing. We find that the GPU algorithm achieves superior performance over the baseline parallel CPU implementation, achieving a speedup of up to 174.53 × . The Vera C. Rubin Observatory will carry out the Legacy Survey of Space and Time (LSST). We perform an analysis that shows we can derive the rotation periods of batches of Solar System objects at LSST scale in near real-time, which will be employed in a future LSST event broker. All source codes have been made publicly available.

Infrared spectroscopy of clathrate hydrates for planetary science: the ethylene case

ABSTRACT Hydrocarbons are observed in the gas or solid phases of Solar system objects, including comets, Trans-Neptunian Objects, planets, and their moons. In the presence of water ice in these environments, hydrocarbons-bearing clathrate hydrates could form. In clathrate hydrates, guest molecules are trapped in crystalline water cages of different sizes, a phase used in models of planetary (sub-)surfaces or icy bodies such as comets. The phases in presence, the potential estimate of abundances of hydrocarbon species, and the spectroscopic behaviour of hydrocarbon species in the different phases must be recorded to provide reference spectra for the comparison with remote observations. We show in this study the specific encaged ethylene signatures, with bands similar in position, but shifted from the pure ethylene ice spectrum. They show a marked temperature dependence both in position and width. Some vibrational modes are activated in the infrared by interaction with the water ice cages.

The determination of asteroid H and G phase function parameters using Gaia DR2

ABSTRACT The Gaia mission will provide the scientific community with high-quality observations of asteroids of all categories. The second release of Gaia data (DR2) was published in 2018 and consists of 22 months of observations of 14 099 known Solar system objects, mainly asteroids. The purpose of this work is to obtain a catalogue of phase function parameters (H and G) for all the asteroids that were observed during the Gaia mission and that were published in DR2. For this purpose, we introduce an algorithm capable of building this catalogue from the magnitude and UTC epoch data present in the DR2 data base. Because Gaia will never observe asteroids with a phase angle of 0° (corresponding to opposition), but with phase angles higher than 10°, we added data from ground observations (corresponding to small phase angles) and thus improved the determination of the H and G parameters of the phase function. We also built a catalogue of the parameters of the H, G1 andG2 phase function. We compared our results of the H, G functions with those of the Astorb data base and observed that the level of agreement is satisfactory.

Potential asteroid discoveries by the ESA Gaia mission

Context. Since July 2014, the Gaia mission of the European Space Agency has been surveying the entire sky down to magnitude 20.7 in the visible. In addition to the millions of daily observations of stars, thousands of Solar System objects (SSOs) are observed. By comparing their positions, as measured by Gaia, to those of known objects, a daily processing pipeline filters known objects from potential discoveries. However, owing to Gaia’s specific observing mode, which follows a predetermined scanning law designed for stars as “fixed” objects on the celestial sphere, potential newly discovered moving objects are characterized by very few observations, which are acquired over a limited time. Furthermore, these objects cannot be specifically targeted by Gaia itself after their first detection. This aspect was recognized early on in the design of the Gaia data processing. Aims. A daily processing pipeline dedicated to these candidate discoveries was set up to release calls for observations to a network of ground-based telescopes. Their aim is to acquire follow-up astrometry and to characterize these objects. Methods. From the astrometry measured by Gaia, preliminary orbital solutions are determined, allowing us to predict the position of these potentially newly discovered objects in the sky while accounting for the large parallax between Gaia and the Earth (separated by 0.01 au). A specific task within the Gaia Data Processing and Analysis Consortium has been responsible for the distribution of requests for follow-up observations of potential Gaia SSO discoveries. Since late 2016, these calls for observations (nicknamed “alerts”) have been published via a Web interface with a quasi-daily frequency, together with observing guides, which is freely available to anyone worldwide. Results. Between November 2016 and the end of the first year of the extended mission (July 2020), over 1700 alerts were published, leading to the successful recovery of more than 200 objects. Among them, six have a provisional designation assigned with the Gaia observations; the others were previously known objects with poorly characterized orbits, precluding identification at the time of Gaia observations. There is a clear trend for objects with a high inclination to be unidentified, revealing a clear bias in the current census of SSOs against high-inclination populations.

Microbially-Enhanced Vanadium Mining and Bioremediation Under Micro- and Mars Gravity on the International Space Station.

As humans explore and settle in space, they will need to mine elements to support industries such as manufacturing and construction. In preparation for the establishment of permanent human settlements across the Solar System, we conducted the ESA BioRock experiment on board the International Space Station to investigate whether biological mining could be accomplished under extraterrestrial gravity conditions. We tested the hypothesis that the gravity (g) level influenced the efficacy with which biomining could be achieved from basalt, an abundant material on the Moon and Mars, by quantifying bioleaching by three different microorganisms under microgravity, simulated Mars and Earth gravitational conditions. One element of interest in mining is vanadium (V), which is added to steel to fabricate high strength, corrosion-resistant structural materials for buildings, transportation, tools and other applications. The results showed that Sphingomonas desiccabilis and Bacillus subtilis enhanced the leaching of vanadium under the three gravity conditions compared to sterile controls by 184.92 to 283.22%, respectively. Gravity did not have a significant effect on mean leaching, thus showing the potential for biomining on Solar System objects with diverse gravitational conditions. Our results demonstrate the potential to use microorganisms to conduct elemental mining and other bioindustrial processes in space locations with non-1 × g gravity. These same principles apply to extraterrestrial bioremediation and elemental recycling beyond Earth.

Second Data Release of the All-sky NOIRLab Source Catalog

Abstract We announce the second data release (DR2) of the NOIRLab Source Catalog (NSC), using 412,116 public images from CTIO-4 m+DECam, the KPNO-4 m+Mosaic3, and the Bok-2.3 m+90Prime. NSC DR2 contains over 3.9 billion unique objects, 68 billion individual source measurements, covers ≈35,000 square degrees of the sky, has depths of ≈23 mag in most broadband filters with ≈1%–2% photometric precision, and astrometric accuracy of ≈7 mas. Approximately 1.9 billion objects within ≈30,000 square degrees of sky have photometry in three or more bands. There are several improvements over NSC DR1. DR2 includes 156,662 (61%) more exposures extending over 2 more years than in DR1. The southern photometric zero-points in griz are more accurate by using the Skymapper DR1 and ATLAS-Ref2 catalogs, and improved extinction corrections were used for high-extinction regions. In addition, the astrometric accuracy is improved by taking advantage of Gaia DR2 proper motions when calibrating the astrometry of individual images. This improves the NSC proper motions to ∼2.5 mas yr−1 (precision) and ∼0.2 mas yr−1 (accuracy). The combination of sources into unique objects is performed using a DBSCAN algorithm and mean parameters per object (such as mean magnitudes, proper motion, etc.) are calculated more robustly with outlier rejection. Finally, eight multi-band photometric variability indices are calculated for each object and variable objects are flagged (23 million objects). NSC DR2 will be useful for exploring solar system objects, stellar streams, dwarf satellite galaxies, quasi-stellar objects, variable stars, high proper-motion stars, and transients. Several examples of these science use cases are presented. The NSC DR2 catalog is publicly available via the NOIRLab’s Astro Data Lab science platform.

Far-infrared imager and polarimeter for the Origins Space Telescope

The far-infrared imager and polarimeter (FIP) for the Origins Space Telescope (Origins) is a basic far-infrared imager and polarimeter. The camera will deliver continuum images and polarization measurements at 50 and 250 μm. Currently available detector technologies provide sufficient sensitivity for background limited observations from space, at least on a single pixel basis. FIP incorporates large next-generation superconducting detector arrays and our technology development plan will push the pixel numbers for the arrays to the required size of 8000. Two superconducting detector technologies are currently candidates for the instrument: transition edge sensors or microwave kinetic inductance devices. Using these detectors and taking advantage of the cryogenic telescope that is provided by Origins, FIP will achieve mapping speeds of up to eight orders of magnitude faster than what has been achieved by existing observatories. The science drivers for FIP include observations of solar system objects, dust properties, and magnetic field studies of the nearby interstellar medium, and large scale galaxy surveys to better constrain the star formation history of the universe to address one of the main themes of Origins: “How does the Universe work?” In addition to the science, the FIP instrument plays a critical functional role in aligning the mirrors during on orbit observatory commissioning.

NEOExchange - an online portal for NEO and Solar System science

Las Cumbres Observatory (LCO) has deployed a homogeneous telescope network of ten 1-m telescopes to four locations in the northern and southern hemispheres, with a planned network size of twelve 1-m telescopes at 6 locations. This network is very versatile and is designed to respond rapidly to target of opportunity events and also to perform long term monitoring of slowly changing astronomical phenomena. The global coverage, available telescope apertures, and flexibility of the LCO network make it ideal for discovery, follow-up, and characterization of Solar System objects such as asteroids, Kuiper Belt Objects, comets, and especially Near-Earth Objects (NEOs).We describe the development of the “LCO NEO Follow-up Network” which makes use of the LCO network of robotic telescopes and an online, cloud-based web portal, NEOexchange, to perform photometric characterization and spectroscopic classification of NEOs and follow-up astrometry for both confirmed NEOs and unconfirmed NEO candidates.The follow-up astrometric, photometric, and spectroscopic characterization efforts are focused on those NEO targets that are due to be observed by the planetary radar facilities and those on the Near-Earth Object Human Space Flight Accessible Targets Study (NHATS) lists. Our astrometric observations allow us to improve target orbits, making radar observations possible for objects with a short arc or large orbital uncertainty, which could be greater than the radar beam width. Astrometric measurements also allow for the detection and measurement of the Yarkovsky effect on NEOs. The photometric and spectroscopic data allows us to determine the light curve shape and amplitude, measure rotation periods, determine the taxonomic classification, and improve the overall characterization of these targets. We are also using a small amount of the LCO NEO Follow-up Network time to confirm newly detected NEO candidates produced by the major sky surveys such as ATLAS, Catalina Sky Survey (CSS) and PanSTARRS (PS1). We will describe the construction of the NEOexchange NEO follow-up portal and the development and deployment methodology adopted which allows the software to be packaged and deployed anywhere, including in off-site cloud services. This allows professionals, amateurs, and citizen scientists to plan, schedule and analyze NEO imaging and spectroscopy data using the LCO network and acts as a coordination hub for the NEO follow-up efforts. We illustrate the capabilities of NEOexchange and the LCO NEO Follow-up Network with examples of first period determinations for radar-targeted NEOs and its use to plan and execute multi-site photometric and spectroscopic observations of (66391) 1999 KW4, the subject of the most recent planetary defense exercise campaign.

Small Solar System objects on highly inclined orbits

Context. Less than one percent of the discovered small Solar System objects have highly inclined orbits (i > 60°), and revolve around the Sun on near-polar or retrograde orbits. The origin and evolutionary history of these objects are not yet clear. Aims. In this work we study the surface properties and orbital dynamics of selected high-inclination objects. Methods. BVRI photometric observations were performed in 2019–2020 using the 2.0 m telescope at the Terskol Observatory and the 2.6 m telescope at the Crimean Astrophysical Observatory. Additionally, we searched for high-inclination objects in the Sloan Digital Sky Survey and Pan-STARRS. The dynamics of the selected objects was studied using numerical simulations. Results. We obtained new photometric observations of six high-inclination objects (468861) 2013 LU28, (517717) 2015 KZ120, 2020 EP, A/2019 U5 (A/PanSTARRS), C/2018 DO4 (Lemmon), and C/2019 O3 (Palomar). All of the objects have similar B−V, V −R, R−I colours, which are close to those of moderately red TNOs and grey Centaurs. The photometric data that were extracted from the all-sky surveys also correspond to moderately red surfaces of high-inclination objects. No signs of ultra-red material on the surface of high-inclination asteroids were found, which supports the results of previous works. The comet C/2018 DO4 (Lemmon) revealed some complex morphology with structures that could be associated with particles that were ejected from the cometary nucleus. Its value of the parameter Afρ is around 100 cm for the aperture size of 6000 km. The value of Afρ for the hyperbolic comet C/2019 O3 (Palomar) is much larger, and is in the range from 2000 to 3700 cm for the aperture sizes from 25 000 to 60 000 km. For objects 2013 LU28, 2015 KZ120, and 2020 EP we estimated future and past lifetimes on their orbits. It appears that the orbits of considered objects are strongly chaotic, and with the available accuracy of the orbital elements no reliable predictions can be made about their distant past or future. The lifetimes of high-inclination objects turned out to be highly non-sensitive to the precision of the orbital elements, and to the Yarkovsky orbital drift.

A Two-stage Deep Learning Detection Classifier for the ATLAS Asteroid Survey

In this paper we present a two-step neural network model to separate detections of solar system objects from optical and electronic artifacts in data obtained with the “Asteroid Terrestrial-impact Last Alert System” (ATLAS), a near-Earth asteroid sky survey system. A convolutional neural network is used to classify small “postage-stamp” images of candidate detections of astronomical sources into eight classes, followed by a multi-layered perceptron that provides a probability that a temporal sequence of four candidate detections represents a real astronomical source. The goal of this work is to reduce the time delay between Near-Earth Object (NEO) detections and submission to the Minor Planet Center. Due to the rare and hazardous nature of NEOs, a low false negative rate is a priority for the model. We show that the model reaches 99.6% accuracy on real asteroids in ATLAS data with a 0.4% false negative rate. Deployment of this model on ATLAS has reduced the amount of NEO candidates that astronomers must screen by 90%, thereby bringing ATLAS one step closer to full autonomy.

Resolved molecular line observations reveal an inherited molecular layer in the young disk around TMC1A

Context.Physical processes that govern the star and planet formation sequence influence the chemical composition and evolution of protoplanetary disks. Recent studies allude to an early start to planet formation already during the formation of a disk. To understand the chemical composition of protoplanets, we need to constrain the composition and structure of the disks from whence they are formed.Aims.We aim to determine the molecular abundance structure of the young disk around the TMC1A protostar on au scales in order to understand its chemical structure and any possible implications for disk formation.Methods.We present spatially resolved Atacama Large Millimeter/submillimeter Array observations of CO, HCO+, HCN, DCN, and SO line emission, as well as dust continuum emission, in the vicinity of TMC1A. Molecular column densities are estimated both under the assumption of optically thin emission from molecules in local thermodynamical equilibrium (LTE) as well as through more detailed non-LTE radiative transfer calculations.Results.Resolved dust continuum emission from the disk is detected between 220 and 260 GHz. Rotational transitions from HCO+, HCN, and SO are also detected from the inner 100 au region. We further report on upper limits to vibrational HCNυ2= 1, DCN, and N2D+lines. The HCO+emission appears to trace both the Keplerian disk and the surrounding infalling rotating envelope. HCN emission peaks toward the outflow cavity region connected with the CO disk wind and toward the red-shifted part of the Keplerian disk. From the derived HCO+abundance, we estimate the ionization fraction of the disk surface, and find values that imply that the accretion process is not driven by the magneto-rotational instability. The molecular abundances averaged over the TMC1A disk are similar to its protostellar envelope and other, older Class II disks. We meanwhile find a discrepancy between the young disk’s molecular abundances relative to Solar System objects.Conclusions.Abundance comparisons between the disk and its surrounding envelope for several molecular species reveal that the bulk of planet-forming material enters the disk unaltered. Differences in HCN and H2O molecular abundances between the disk around TMC1A, Class II disks, and Solar System objects trace the chemical evolution during disk and planet formation.

(85989) 1999 JD6: a first Barbarian asteroid detected by polarimetry in the NEA population

Context.To investigate the physical properties of the surface layers of small Solar System objects, we take advantage of the phase-angle dependence of the linear polarization degree, which varies with albedo, composition, and other factors. In particular, the angle at which the positive and negative are reversed is a polarimetric parameter known as inversion angle. A group with large inversion angles (the so-called Barbarians) is unusual and is also noteworthy because of their association with meteorites.Aims.We identified an object with such a large inversion angle in the near-Earth asteroids and derived previously unknown parameters, including the maximum polarization degree. By comparing the polarimetric parameters and spectral properties of meteorites, we inferred the surface conditions based on the degree of polarization of the asteroid.Methods.We carried out multiband polarization imaging observations of an L-type near-Earth asteroid, (85989) 1999 JD6, at the Hokkaido University Observatory in 2015 and 2019, covering a wide range of phase angles 30°–105°. Of the polarimetric parameters, we derived the maximum value, inversion angle, and the slope at that angle from the phase angle-polarization degree curve.Results.We found that the inversion angle and the maximum polarization degree of 1999 JD6are 27° and 13%. The inversion angle is significantly larger than those of the majority of all asteroids observed before, but is consistent with that of Barbarian asteroids. 1999 JD6is the first example belonging to this group that is also among the near-Earth asteroids.Conclusions.We claim that 1999 JD6is a member of the Barbarians and has rougher surface particles than lunar regolith.

The Sizes and Albedos of Centaurs 2014 YY49 and 2013 NL24 from Stellar Occultation Measurements by RECON

Abstract In 2019, the Research and Education Collaborative Occultation Network (RECON) obtained multiple-chord occultation measurements of two Centaur objects: 2014 YY49 on 2019 January 28 and 2013 NL24 on 2019 September 4. RECON is a citizen-science telescope network designed to observe high-uncertainty occultations by outer solar system objects. Adopting circular models for the object profiles, we derive a radius km and a geometric albedo for 2014 YY49 and a radius km and a geometric albedo for 2013 NL24. To the precision of these measurements, no atmosphere or rings are detected for either object. The two objects measured here are among the smallest distant objects measured with the stellar occultation technique. In addition to these geometric constraints, the occultation measurements provide astrometric constraints for these two Centaurs at a higher precision than has been feasible by direct imaging. To supplement the occultation results, we also present an analysis of color photometry from the Pan-STARRS surveys to constrain the rotational light curve amplitudes and spectral colors of these two Centaurs. We recommend that future work focus on photometry to more deliberately constrain the objects’ colors and light curve amplitudes and on follow-on occultation efforts informed by this astrometry.

Energetic ion irradiation of N2O ices relevant for Solar system surfaces

ABSTRACT Ices are the dominant surface material of many Solar system objects, such as comets and trans-Neptunian objects. They are continuously exposed to ion bombardment by solar wind ions and cosmic rays, which trigger secondary ion emission, contributing to the exosphere formation. Laboratory studies demonstrated the effects of energetic processing of ices at low temperature, showing the production of molecules and free radicals of astrophysical interest. Nitrous oxide (N2O) is one of the molecular species observed in star-forming sites, reason why it may be present in the ices covering some minor bodies in the outer Solar system. In the current work, N2O ice at 10 K was irradiated by energetic (MeV/u) multicharged heavy ions (e.g. 105Rh and 140Ba); the sputtered species were detected and analysed by the TOF-PDMS technique (time-of-flight plasma desorption mass spectrometry). Small positive and negative secondary ions were identified: N+, N2+, NO+, O+, and O−. The bombardment also induces production of ion cluster series: (N2)nR$_{m}^+$, (NO)nR$_{m}^+$, (N2O)nR$_{m}^+$, where R = N+, N2+, NO+, N2O+, Om+ (n up to ∼ 10, m = 1−3). Their yield distributions follow the sum of two decreasing exponentials, one fast -F and another slow -S, suggesting a two-regime formation. Most of the yield distributions have the same pair of exponential decay constants, around kF ∼ 1.4 and kS ∼ 0.15 u−1. Based on this behavior, an emission description for aggregates is proposed, useful to understand the processes by which neutral and ionized molecular species are delivery to the gas phase in space.