Solar System Objects Research Articles

QCMOS Detectors and the Case of Hypothetical Primordial Black Holes in the Solar System, near Earth Objects, Transients, and Other High-cadence Observations

Abstract Recent progress with CMOS detector development has opened new parameter space for high cadence time resolved imaging of transients and fast proper motion solar system objects. Using computer simulations for a ground-based 1.23 m telescope, this research note illustrates the gain of a new generation of fast readout low noise qCMOS sensors over CCDs and makes the case for high precision monitoring of asteroid orbits that can potentially shed light on the hypothetical existence of low mass primordial black holes, as well as for other applications requiring high speed imaging.

Limits to dynamic range in GHz-THz single-dish planetary spectra

Abstract When bright solar-system objects are observed by GHz-THz regime telescopes, off-axis signals bounce around locally and re-enter the signal path with a time delay, causing sinusoidal ripples in output spectra. Ripples that are unstable over time are challenging to remove. A typical detection limit for planetary spectral lines is a fraction ∼10−3 of continuum signal, restricting searches for minor atmospheric trace-gases. Modern wideband spectra of Venus demonstrate a plethora of effects, at three example telescopes spanning nearly a factor-of-50 in frequency. Characterisation of instrumental effects as families of pure sine-waves via Fourier-analysis is shown to improve dynamic-range by factors of a few. An example upper limit on sulphuric acid (H2SO4) vapour in Venus’ mesosphere, from fully-automated data-cleaning of a 3.5 GHz band containing 10 line components, goes as deep as the best previously-published limit. The most challenging cases are searches for single lines of width comparable to ripple periods. Traditional polynomial-fitting approaches can be deployed to test for false positives, to demonstrate robustness at a level of zero ”fake lines” in >1000 comparisons. Fourier-based data-cleaning avoids subjectivity and can be fully automated, and synthetic spectra can be injected before processing to test to what degree signals are lost in cleaning. An ideal robustness strategy is mitigation at the data-acquisition stage, e.g. using slow drifts in target-velocity with respect to the telescope to isolate a planetary line from a quasi-static instrumental ripple pattern.

Visible-light High-contrast Imaging and Polarimetry with SCExAO/VAMPIRES

We present significant upgrades to the Visible Aperture-Masking Polarimetric Imager/Interferometer for Resolving Exoplanetary Signatures (VAMPIRES) instrument, a visible-light (600–800 nm) high-contrast imaging polarimeter integrated within SCExAO on the Subaru telescope. Key enhancements include new qCMOS detectors, coronagraphs, polarization optics, and a multiband imaging mode, improving sensitivity, resolution, and efficiency. These upgrades position VAMPIRES as a powerful tool for studying sub-stellar companions, accreting protoplanets, circumstellar disks, stellar jets, stellar mass-loss shells, and solar system objects. The instrument achieves angular resolutions from 17 to 21 mas and Strehl ratios up to 60%, with 5σ contrast limits of 10−4 at 0.″1 to 10−6 beyond 0.″5. We demonstrate these capabilities through spectro-polarimetric coronagraphic imaging of the HD 169142 circumstellar disk, ADI+SDI imaging of the sub-stellar companion HD 1160B, narrowband Hα imaging of the R Aqr emission nebula, and spectro-polarimetric imaging of Neptune.

Machine learning methods for automated interstellar object classification with LSST

The Legacy Survey of Space and Time (LSST), to be conducted with the Vera C. Rubin Observatory, is poised to revolutionize our understanding of the Solar System by providing an unprecedented wealth of data on various objects, including the elusive interstellar objects (ISOs). Detecting and classifying ISOs is crucial for studying the composition and diversity of materials from other planetary systems. However, the rarity and brief observation windows of ISOs, coupled with the vast quantities of data to be generated by LSST, create significant challenges for their identification and classification. This study aims to address these challenges by exploring the application of machine learning algorithms to the automated classification of ISO tracklets in simulated LSST data. We employed various machine learning algorithms, including random forests (RFs), stochastic gradient descent (SGD), gradient boosting machines (GBMs), and neural networks (NNs), to classify ISO tracklets in simulated LSST data. Our results demonstrate that GBM and RF algorithms outperform SGD and NN algorithms in accurately distinguishing ISOs from other Solar System objects. RF analysis shows that many derived Digest2 values are more important than direct observables (right ascension, declination, and magnitude) in classifying ISOs from the LSST tracklets. The GBM model achieves the highest precision, recall, and F1 score, with values of 0.9987, 0.9986, and 0.9987, respectively. These findings lay the foundation for the development of an efficient and robust automated system for ISO discovery using LSST data, paving the way for a deeper understanding of the materials and processes that shape planetary systems beyond our own. The integration of our proposed machine learning approach into the LSST data processing pipeline will optimize the survey's potential for identifying these rare and valuable objects, enabling timely follow-up observations and further characterization.

The DECam Ecliptic Exploration Project (DEEP). VII. The Strengths of Three Superfast Rotating Main-belt Asteroids from a Preliminary Search of DEEP Data

Superfast rotators (SFRs) are small solar system objects that rotate faster than generally possible for a cohesionless rubble pile. Their rotational characteristics allow us to make inferences about their interior structure and composition. Here, we present the methods and results from a preliminary search for SFRs in the DECam Ecliptic Exploration Project (DEEP) data set. We find three SFRs from a sample of 686 main-belt asteroids, implying an occurrence rate of 0.4−0.3+0.1 %—a higher incidence rate than has been measured by previous studies. We suggest that this high occurrence rate is due to the small sub-kilometer size regime to which DEEP has access: the objects searched here were as small as ∼500 m. We compute the minimum required cohesive strength for each of these SFRs and discuss the implications of these strengths in the context of likely evolution mechanisms. We find that all three of these SFRs require strengths that are more than that of weak regolith but consistent with many cohesive asteroid strengths reported in the literature. Across the full DEEP data set, we have identified ∼70,000 Main-Belt Asteroids and expect ∼300 SFRs—a result that will be assessed in a future paper.

New astrometric positions for six Jovian irregular satellites using Gaia DR3 in 2016 — 2021

The Jovian system is like a miniature solar system, with the system being more than twice as massive as all the other planets combined and having many natural satellites. Its formation and early evolution had a profound influence on our knowledge of the sculpting of the architecture of the solar system. Astrometric observations are of importance, based on these observations, its orbital dynamics, as well as its origin sometimes, of a solar system object can be determined. We aimed to obtain good astrometric positions of some irregular satellites Elara, Pasiphae, Sinope, Lysithea, Carme and Ananke to refine their orbits and ephemerides, and to understand their dynamics. We have taken, processed and reduced 964 ground-based CCD frames obtained between 2016 and 2021 by the 2.4 m telescope at the Lijiang Station of Yunnan Observatory over 27 nights. Among CCD image processing, the image subtraction technique of ISIS is employed to eliminate star images that are close to or/and almost overlapped with those of our targets in 2019. The star catalog Gaia DR3 is utilized for astrometric calibration, in which a weight scheme is applied to solve more accurate plate model. For all targets, their theoretical positions are retrieved from the Institut de Mécanique Céleste et de Calcul des Éphémérides (IMCCE) ephemeris. Our results show the mean (O - C)s (observed minus computed) of the positional residuals of all targets are −0′′.007 and 0′′.011 in R.A. and Dec., respectively. Their corresponding standard deviations are about 0′′.05 in each direction, except for Ananke (the faintest satellite) with its standard deviation about 0′′.08 in each direction.

Forming Massive Terrestrial Satellites through Binary-exchange Capture

The number of planetary satellites around solid objects in the inner solar system is small either because they are difficult or unlikely to form or because they do not survive for astronomical timescales. Here we conduct a pilot study on the possibility of satellite capture from the process of collision-less binary exchange and show that massive satellites in the range 0.01–0.1 M ⊕ can be captured by Earth-sized terrestrial planets in a way already demonstrated for larger planets in the solar system and possibly beyond. In this process, one of the binary objects is ejected, leaving the other object as a satellite in orbit around the planet. We specifically consider satellite capture by an “Earth” in an assortment of hypothetical encounters with large terrestrial binaries at 1 au around the Sun. In addition, we examine the tidal evolution of captured objects and show that orbit circularization and long-term stability are possible for cases resembling the Earth–Moon system.

The Solar System Notification Alert Processing System (SNAPS): Asteroid Population Outlier Detection

The Solar system Notification Alert Processing System (snaps) is a Zwicky Transient Facility (ZTF) and Rubin Observatory alert broker that will send alerts to the community regarding interesting events in the solar system. snaps is actively monitoring solar system objects and one of its functions is to compare objects (primarily main belt asteroids) to one another to find those that are outliers relative to the population. In this paper, we use the SNAPShot1 data set, which contains 31,693 objects from ZTF, and derive outlier scores for each of these objects. snaps employs an unsupervised approach; consequently, to derive outlier rankings for each object, we propose four different outlier metrics such that we can explore variants of the outlier scores and add confidence to the outlier rankings. We also provide outlier scores for each object in each permutation of 15 feature spaces, between two and 15 features, which yields 32,752 total feature spaces. We show that we can derive population outlier rankings each month at Rubin Observatory scale using four Nvidia A100 GPUs, and present several avenues of scientific investigation that can be explored using population outlier detection.

The Discovery and Evolution of a Possible New Epoch of Cometary Activity by the Centaur (2060) Chiron

Centaurs are small solar system objects on chaotic orbits in the giant planet region, forming an evolutionary continuum with the Kuiper Belt objects and Jupiter-family comets. Some Centaurs are known to exhibit cometary activity, though unlike comets, this activity tends not to correlate with heliocentric distance, and the mechanism behind it is currently poorly understood. We utilize serendipitous observations from the Asteroid Terrestrial-impact Last Alert System, Zwicky Transient Facility, Panoramic Survey Telescope and Rapid Response System, Dark Energy Survey, and Gaia in addition to targeted follow-up observations from the Las Cumbres Observatory, TRAnsiting Planets and PlanetesImals Small Telescope South (TRAPPIST-South), and Gemini North telescope to analyze an unexpected brightening exhibited by the known active Centaur (2060) Chiron in 2021. This is highly indicative of a cometary outburst. As of 2023 February, Chiron had still not returned to its prebrightening magnitude. We find Chiron's rotational lightcurve, phase curve effects, and possible high-albedo surface features to be unlikely causes of this observed brightening. We consider the most likely cause to be an epoch of either new or increased cometary activity, though we cannot rule out a possible contribution from Chiron's reported ring system, such as a collision of as-yet-unseen satellites shepherding the rings. We find no evidence for a coma in our Gemini or TRAPPIST-South observations, though this does not preclude the possibility that Chiron is exhibiting a coma that is too faint for observation or constrained to the immediate vicinity of the nucleus.

Predictions for Sparse Photometry of Jupiter-family Comet Nuclei in the LSST Era

The Legacy Survey of Space and Time (LSST) at Vera C. Rubin Observatory will deliver high-quality, temporally sparse observations of millions of solar system objects on an unprecedented scale. Such data sets will likely enable the precise estimation of small-body properties on a population-wide basis. In this work, we consider the possible applications of photometric data points from LSST to the characterization of Jupiter-family comet (JFC) nuclei. We simulate sparse-in-time lightcurve points with an LSST-like cadence for the orbit of a JFC between 2024 and 2033. Convex lightcurve inversion is used to assess whether the simulation input parameters can be accurately reproduced for a sample of nucleus rotation periods, pole orientations, activity onsets, shapes, and sizes. We find that the rotation period and pole direction can be reliably constrained across all nucleus variants tested, and that the convex shape models, while limited in their ability to describe complex or bilobed nuclei, are effective for correcting sparse photometry for rotational modulation to improve estimates of nucleus phase functions. Based on this analysis, we anticipate that LSST photometry will significantly enhance our present understanding of the spin state and phase function distributions of JFC nuclei.

Combined spin orientation and phase function of asteroids

Context. Large sky surveys provide numerous non-targeted observations of small bodies of the Solar System. The upcoming LSST of the Vera C. Rubin Observatory will be the largest source of small body photometry in the next decade. With non-coordinated epochs of observation, colors – and therefore taxonomy and composition – can only be computed by comparing absolute magnitudes obtained in each filter by solving the phase function (evolution of brightness of the small body against the solar phase angle). Current models in use in the community (HG, HG12*, and HG1G2), however, fail to reproduce the long-term photometry of many targets due to the change in the aspect angle between apparitions. Aims. We aim to derive a generic yet simple phase function model accounting for the variable geometry of the small bodies over multiple apparitions. Methods. As a spinoff of the HG1 G2 model, we propose the sHG1G2 phase function model in which we introduce a term describing the brightness changes due to spin orientation and polar oblateness. We applied this new model to 13 245 908 observations of 122 675 Solar System objects (SSOs). These observations were acquired in the g and r filters with the Zwicky Transient Facility between November 1, 2019 and December 1, 2023. We retrieved them and implemented the new sHG1G2 model in FINK, a broker of alerts designed for the LSST. Results. The sHG1G2 model leads to smaller residuals than other phase function models, providing a better description of the photometry of asteroids. We determined the absolute magnitude, H, and phase function coefficients (G1, G2) in each filter, the spin orientation (α0, δ0), and the polar-to-equatorial oblateness, R, for 95 593 SSOs, which constitutes about a tenfold increase in the number of characterized objects compared to the current census. Conclusions. The application of the sHG1 G2 model to ZTF alert data using the FINK broker shows that the model is appropriate for extracting physical properties of asteroids from multi-band and sparse photometry, such as the forthcoming LSST survey.

Chrome-rich spinels in micrometeorites from modern Antarctic sedimentary deposits

Each year, approximately 5000 tons of extraterrestrial material reaches the Earth's surface as micrometeorites, cosmic dust particles ranging from 10 to 2000 μm in size. These micrometeorites, collected from diverse environments, mainly deep-sea sediments, Antarctic ice, snow and loose sediments, and hot deserts, are crucial in understanding our Solar System's evolution. Chrome-rich spinel (Cr-spinel) minerals have gained attention as proxies for studying the extraterrestrial flux in sedimentary deposits, because these robust minerals occur, in various extraterrestrial materials, with compositions characteristic of their parent bodies. A total of 27 Cr-spinel bearing micrometeorites within the size range of 185–800 μm, were identified from approximately 6000 micrometeorites from the Transantarctic Mountains (n = 23) and the Sør Rondane Mountains (n = 4), in Antarctica, containing Cr-spinel (8–120 μm), were examined in this study for geochemical composition and high-precision oxygen isotope ratios to assess alteration and identify potential parent bodies.Oxygen isotopes in the micrometeorite groundmass and in Cr-spinel grains reveal a predominance of ordinary chondritic precursors, with only 1 in 10 micrometeorites containing Cr-spinel minerals showing a carbonaceous chondritic signature. This may be further confirmed by an elevated Al content (> 12 wt% Al2O3) in Cr-spinel from specific carbonaceous chondrite types, but a more extensive dataset is required to establish definitive criteria. The first Cr-spinel bearing particle, in an Antarctic micrometeorite, that can be linked to R-chondrites based on oxygen isotopes, has been documented, demonstrating the potential for R-chondrites as a source of chrome-rich spinels. The study also highlights the potential for chemical modifications and alteration processes that Cr-spinel minerals may undergo during their time on the parent body, atmospheric entry, and terrestrial residence.In the context of the broader micrometeorite flux, the results align with previous findings, showing a consistent contribution of micrometeorites containing Cr-spinel minerals related to ordinary chondrites over the past 2 to 4 million years. This is however a small fraction (∼ 1 %) of the total micrometeorite flux. The study further confirms that Cr-spinel minerals recovered from sedimentary deposits serve as valuable proxies for tracking events related to ordinary chondritic or achondritic materials. However, it is emphasized that Cr-spinel minerals alone cannot serve as exclusive indicators of the overall extraterrestrial flux, especially during periods dominated by carbonaceous chondritic dust in the inner Solar System. To comprehensively understand the complete extraterrestrial flux, additional proxies are needed to trace dust-producing events associated with various Solar System objects. The intricate nature of Cr-spinel compositions, and the potential for alteration processes emphasize the need for further research to refine our understanding of these extraterrestrial markers.

Gravitational disturbance on asteroidal ring systems by close encounter with a small object

To date, rings are found around a Centaur (10199) Chariklo, trans-neptunian objects (TNOs) (136108) Haumea, and (50000) Quaoar. These discoveries suggest that asteroidal ring systems may be common, particularly in the outer solar system. Since collisions are a ubiquitous and fundamental evolutionary process throughout the solar system, we conjecture that asteroidal ring systems must have experienced close encounters with small objects as part of their evolutionary process. Here, we investigate the response of ring systems when they experience gravitational disturbance by a close encounter with another small object, by calculating the change in eccentricity and the fraction of lost ring particles. We find that a perturber needs to be as massive as or more massive than the ringed object, and needs to pass in the immediate vicinity of the ring in order to cause significant disruption. The change in eccentricity expected for Chariklo's inner ring and Quaoar's outer ring agrees with the analytical expression derived from the impulse approximation, while that for Haumea's ring agrees with the analytical expression called “exponential regime”. If we define a lifetime of a ring as the mean time to experience disruptive close encounters that can raise the eccentricity of ring particles >0.1, the lifetime for ring systems around Chariklo, Haumea, and Quaoar are >104 Gyr. We conclude that ring systems around Chariklo, Haumea, and Quaoar are highly unlikely to suffer from close encounters with another small object even if those systems are as old as 4 Gyr. Close encounter with a small object may not be responsible for the finite eccentricity observed for Chariklo's ring system, although eccentricity of ring particles could be increased to ∼10−4 in 4 Gyr. We also find that the lifetime is shorter for smaller ringed objects, and it still exceeds 4 Gyr for km-sized ringed objects in the outer solar system. Therefore, regardless of the size of ringed objects, asteroidal ring systems in the outer solar system are unlikely to suffer severe damage by close encounter with a small object. On the other hand, the lifetime is estimated to be on the order of 100 Myr for km-sized asteroids and 10 Myr for 100 m-sized asteroids in the near-Earth region and the main belt. This finding offers a dynamical explanation why ring systems have not been found in the inner solar system.

Asteroid spin and shape properties from Gaia DR3 photometry

The third data release of in June 2022, included the first large sample of sparse photometric data for more than 150\,000 Solar System objects (SSOs), mainly asteroids. The SSO photometric data can be processed to derive information on the physical properties for a large number of objects, including spin properties, surface photometric behaviour in a variety of illumination conditions, and overall shape. After selecting a set of 22\,815 objects for which an adequate number of accurate photometric measurements had been obtained by we applied the 'genetic' algorithm of photometric inversion developed by the Data Processing and Analysis Consortium to process SSO photometric data. Given the need to minimise the required data processing time, the algorithm was set to adopt a simple triaxial ellipsoid shape model. Our results show that in spite of the limited variety of observing circumstances and the limited numbers of measurements per object at present (in the majority of cases no greater than $40$ and still far from the number expected at the end of the mission of about $60$ - $70$), the proportion of correct determinations for the spin period among the observed targets is about $85$<!PCT!>. This percentage is based on a comparison with reliable literature data following a moderate filtering procedure developed to remove dubious solutions. The analysis performed in this paper is important in the context of developing further improvements to the adopted data reduction procedure. This includes the possible development of better solution filtering procedures that take into account, for each object, the possible presence of multiple, equivalent spin period solutions that have not been systematically investigated in this preliminary application.

Copper and zinc isotope compositions of pristine eucrites as analogues for differentiated planetary feedstocks

Preferential enrichment of the heavier isotopes of moderately volatile elements (MVE) in samples from asteroids and the Moon have been attributed to volatile loss during the formation and differentiation of their parent bodies. Analogs for planetary feedstocks include the howardite-eucrite-diogenite meteorites, which originate from a differentiated planetesimal or planetesimals, likely including (4) Vesta. Complications arise in the interpretation of volatile depletion in these meteorites, however, due to post-crystallization processes including metamorphism and later impacts that acted upon them. We present new coupled Cu and Zn isotope data for a suite of eucrites that, when combined with published data, show significant ranges (δ65Cu = -1.6 to +0.9‰; δ66Zn = -7.8 to +13.5‰). Exclusion of eucrites that have been affected by metamorphism, impact contamination or surface condensation of isotopically light Zn and Cu leads to a range of ‘pristine’ compositions (δ66Zn = +1.1 ± 2.3‰; δ65Cu = +0.5 ± 0.5‰; 2 St. Dev.), implying inherent MVE variability within the eucrite parent body. As low-mass differentiated bodies, Vesta and the Moon represent endmembers in planet evolution. For the Moon, extensive volatile loss can be explained by a cataclysmic giant impact origin and later magma ocean crystallization. In contrast the parent body of eucrite meteorites likely heterogeneously lost volatile elements and compounds during differentiation. Vesta as the potential source of eucrite meteorites offers an important endmember composition for likely feedstocks to planets, representing the remaining vestige of what was likely to have been a larger population of differentiated objects in the inner Solar System shortly after nebula accretion. Mixing contributions of non-carbonaceous and carbonaceous chondrites constrained by nucleosynthetic Zn isotope anomalies suggests a significant fraction of Earth's accretion could have come from volatile-poor and differentiated planetary feedstocks that would have had limited effects on the bulk silicate Earth (BSE) Zn isotope composition. Furthermore, volatile-poor feedstocks cannot explain the BSE Cu isotope composition, which instead may have been modified by terrestrial core formation. Pristine eucrites offer key insights into early planetesimal differentiation and the role of volatile loss on small mass bodies within nascent solar systems.

Capillary Processes in Extraterrestrial Contexts

AbstractThe Earth is no longer the only known celestial body containing one or more liquid phases. The Cassini spacecraft has discovered seas of hydrocarbons at the surface of Titan, while a series of corroborating evidences argue in favor of the existence of an aqueous ocean beneath the icy crust of several moons. Capillarity embraces a family of physical processes occurring at the free surface of a liquid. These phenomena depend on the liquid properties and on the local planetary conditions. Capillarity may have important direct or indirect implications on the geoscientific and astrobiological points of view. In this paper, we discuss capillarity physics among solar system objects and expected consequences for planetary science.

In Appreciation of Our 2023 Reviewers and Volunteers

AbstractIn JGR‐Planets, the peer review process is critical to ensuring that the published articles are based on sound scientific principles, follow state‐of‐the‐art techniques while acknowledging relevant prior results, and present exciting discoveries or novel understanding of the fundamental processes that affect solar system objects. JGR‐Planets covers a broad range of topics addressing every aspect of geoscience with the only requirement that the work addresses planetary processes. The wide breadth of topics published is reflected by our editorial team composed in 2023 of associate editors Adrian Brown, Jun Cui, Joel Davis, Leigh Fletcher, Matthias Grott, Ananya Mallik, Germán Martínez, Molly McCanta, Katarina Miljkovic, Naomi Murdoch, Ryan Park, Arianna Piccialli, Andrew Poppe, Beatrix Sánchez‐Cano, Laura Schaefer, Mariek Schmidt, Yasuhito Sekine, Kelsi Singer, Michael Sori, Norihiko Sugimoto, Sonia Tikoo, David Trang, and Zhiyong Xiao in addition to the editors who authored this note. We rely on the expertise of the community to vet the articles submitted to the journal. In 2023, JGR‐Planets benefited from 1,184 reviews provided by 731 unique volunteer referees. We also received help from 19 guest editors working on four active special collections. To these volunteers: We are truly grateful that you chose to dedicate your time and energy to evaluate manuscripts and to advise us on the suitability of each manuscript for JGR‐Planets, often suggesting ways to improve the papers. We know that all our volunteers juggle many duties, both professional and personal. On behalf of the entire editorial board of JGR‐Planets, we express our heartfelt gratitude to the many scientists who support this journal. Thank you! You are performing a valued service to this journal and to the community.

Observing gravitational waves with solar system astrometry

The subtle influence of gravitational waves on the apparent positioning of celestial bodies offers novel observational windows [1,2,3,4]. We calculate the expected astrometric signal induced by an isotropic Stochastic Gravitational Wave Background (SGWB) in the short distance limit. Our focus is on the resultant proper motion of Solar System objects, a signal on the same time scales addressed by Pulsar Timing Arrays (PTA). We derive the corresponding astrometric deflection patterns, finding that they manifest as distinctive dipole and quadrupole correlations or, in some cases, may not be present. Our analysis encompasses both Einsteinian and non-Einsteinian polarisations. We estimate the upper limits for the amplitude of SGWBs that could be obtained by tracking the proper motions of large numbers of solar system objects such as asteroids. We find that for SGWBs with negative spectral indices, such as that generated by Super Massive Black Hole Binaries (SMBHB), the constraints from these observations could rival those from PTAs. With the Gaia satellite and the Vera C. Rubin Observatory poised to track an extensive sample of asteroids — ranging from 𝒪(105) to 𝒪(106), we highlight the significant future potential for similar surveys to contribute to our understanding of the SGWB.

Thermal Oxidation Reaction between NH3 and O3: Low-temperature Formation of an NH4+ -bearing Salt

NH3 has long been predicted to be an important component of outer solar system bodies, yet detection of this compound suggests a low abundance or absence on many objects where it would be expected. Here, we demonstrate that a thermally driven oxidation reaction between ammonia (NH3) and ozone (O3) in a H2O + NH3 + O3 mixture may contribute to the low abundance of NH3 on some of these objects, as this reaction efficiently occurs at temperatures as low as 70 K. We determined the overall activation energy for this reaction to be 17 ± 2 kJ mol−1, which is consistent with other chemical systems that react at cryogenic temperatures. The loss of these two compounds coincides with the formation of NH4+ and NO3− at low temperatures, both of which are observable with infrared spectroscopy. Warming our H2O + NH3 + O3 mixtures through sublimation, we find a number of higher-temperature phases, such as ammonia hemihydrate, nitric acid, and ammonium nitrate (NH4NO3). The most stable of these is NH4NO3, which remains on the substrate until temperatures near 270 K. The salt product within this sample contains near-infrared spectral features between 2.0 and 2.22 μm, which is a spectral region of interest for several outer solar system objects, including the Uranian satellites Miranda, Ariel and Umbriel, and Pluto's satellite Charon.

The Impact of Cometary “Impacts” on the Chemistry, Climate, and Spectra of Hot Jupiter Atmospheres

Impacts from icy and rocky bodies have helped shape the composition of Solar System objects; for example, the Earth–Moon system, or the recent impact of comet Shoemaker–Levy 9 with Jupiter. It is likely that such impacts also shape the composition of exoplanetary systems. Here, we investigate how cometary impacts might affect the atmospheric composition/chemistry of hot Jupiters, which are prime targets for characterization. We introduce a parameterized cometary impact model that includes thermal ablation and pressure driven breakup, which we couple with the 1D “radiative-convective” atmospheric model ATMO, including disequilibrium chemistry. We use this model to investigate a wide range of impactor masses and compositions, including those based on observations of Solar System comets, and interstellar ices (with JWST). We find that even a small impactor (R = 2.5 km) can lead to significant short-term changes in the atmospheric chemistry, including a factor >10 enhancement in H2O, CO, and CO2 abundances, as well as atmospheric opacity more generally, and the near-complete removal of observable hydrocarbons, such as CH4, from the upper atmosphere. These effects scale with the change in atmospheric C/O ratio and metallicity. Potentially observable changes are possible for a body that has undergone significant/continuous bombardment, such that the global atmospheric chemistry has been impacted. Our works reveals that cometary impacts can significantly alter or pollute the atmospheric composition/chemistry of hot Jupiters. These changes have the potential to mute/break the proposed link between atmospheric C/O ratio and planet formation location relative to key snowlines in the natal protoplanetary disk.