Solar System Objects Research Articles

Aerial Seismology Using Balloon-Based Barometers

Seismology on Venus has long eluded planetary scientists due to extreme temperature and pressure conditions on its surface, which most electronics cannot withstand for mission durations required for ground-based seismic studies. We show that infrasonic (low-frequency) pressure fluctuations, generated as a result of ground motion, produced by an artificial seismic source known as a seismic hammer, and recorded using sensitive microbarometers deployed on a tethered balloon, are able to replicate the frequency content of ground motion. We also show that weak, artificial seismic activity thus produced may be geolocated by using multiple airborne barometers. The success of this technique paves the way for balloon-based aero-seismology, leading to a potentially revolutionary method to perform seismic studies from a remote airborne station on the earth and solar system objects with substantial atmospheres such as Venus and Titan.

No evidence for true polar wander of Ceres

The spins of solar system objects are not constant with time. One way a world’s spin can change is by true polar wander (TPW), whereby geological activity perturbs the moments of inertia, reorienting the entire body. Recently, Pasquale Tricarico used data from the NASA (National Aeronautics and Space Administration) Dawn mission to propose that Ceres experienced a large amount of TPW. Although their analysis is intriguing, we have identified several flaws that remove the central evidence for TPW of Ceres. Constraining the TPW of Ceres is critically important because TPW could have important consequences for Ceres’s geomorphology, tectonics and volatile content.

World-Universe Model—Alternative to Big Bang Model

This manuscript provides a comparison of the Hypersphere World-Universe Model (WUM) with the prevailing Big Bang Model (BBM) of the Standard Cosmology. The performed analysis of BBM shows that the Four Pillars of the Standard Cosmology are model-dependent and not strong enough to support the model. The angular momentum problem is one of the most critical problems in BBM. Standard Cosmology cannot explain how Galaxies and Extra Solar systems obtained their substantial orbital and rotational angular momenta, and why the orbital momentum of Jupiter is considerably larger than the rotational momentum of the Sun. WUM is the only cosmological model in existence that is consistent with the Law of Conservation of Angular Momentum. To be consistent with this Fundamental Law, WUM discusses in detail the Beginning of the World. The Model introduces Dark Epoch (spanning from the Beginning of the World for 0.4 billion years) when only Dark Matter Particles (DMPs) existed, and Luminous Epoch (ever since for 13.8 billion years). Big Bang discussed in Standard Cosmology is, in our view, transition from Dark Epoch to Luminous Epoch due to Rotational Fission of Overspinning Dark Matter (DM) Supercluster’s Cores. WUM envisions Matter carried from the Universe into the World from the fourth spatial dimension by DMPs. Ordinary Matter is a byproduct of DM annihilation. WUM solves a number of physical problems in contemporary Cosmology and Astrophysics through DMPs and their interactions: Angular Momentum problem in birth and subsequent evolution of Galaxies and Extrasolar systems—how do they obtain it; Fermi Bubbles—two large structures in gamma-rays and X-rays above and below Galactic center; Diversity of Gravitationally-Rounded Objects in Solar system; some problems in Solar and Geophysics [1]. WUM reveals Inter-Connectivity of Primary Cosmological Parameters and calculates their values, which are in good agreement with the latest results of their measurements.

A basin-free spherical shape as an outcome of a giant impact on asteroid Hygiea

(10) Hygiea is the fourth largest main belt asteroid and the only known asteroid whose surface composition appears similar to that of the dwarf planet (1) Ceres1,2, suggesting a similar origin for these two objects. Hygiea suffered a giant impact more than 2 Gyr ago3 that is at the origin of one of the largest asteroid families. However, Hygeia has never been observed with sufficiently high resolution to resolve the details of its surface or to constrain its size and shape. Here, we report high-angular-resolution imaging observations of Hygiea with the VLT/SPHERE instrument (~20 mas at 600 nm) that reveal a basin-free nearly spherical shape with a volume-equivalent radius of 217 ± 7 km, implying a density of 1,944 ± 250 kg m−3 to 1σ. In addition, we have determined a new rotation period for Hygiea of ~13.8 h, which is half the currently accepted value. Numerical simulations of the family-forming event show that Hygiea’s spherical shape and family can be explained by a collision with a large projectile (diameter ~75–150 km). By comparing Hygiea’s sphericity with that of other Solar System objects, it appears that Hygiea is nearly as spherical as Ceres, opening up the possibility for this object to be reclassified as a dwarf planet. SPHERE at the VLT observed Hygiea, the fourth largest body in the main belt and the parent body of a big asteroid family, at unprecedented spatial resolution. Its unexpected spherical shape without any impact crater is explained by numerical simulations with a big impact that fluidized the body, reassembling it in a rotational equilibrium regime.

Default Parallels: The Science Potential of JWST Parallel Observations during TSO Primary Observations

The James Webb Space Telescope (JWST) will observe several stars for long cumulative durations while pursuing exoplanets as primary science targets for both Guaranteed Time Observations (GTO) and very likely General Observer (GO) programs. Here we argue in favor of an automatic default parallel program to observe, e.g., using the F200W/F277W filters or grism of NIRCAM/NIRISS in order to find high redshift (z ≫ 10) galaxies, cool red/brown dwarf substellar objects, solar system objects, and observations of serendipitous planetary transits. We argue here the need for automated exploratory astrophysical observations with unused JWST instruments during these long-duration exoplanet observations. Randomized fields that are observed in parallel mode reduce errors due to cosmic variance more effectively than single continuous fields of a typical wedding cake observing strategy. Hence, we argue that the proposed automated survey will explore a unique and rich discovery space in the high-redshift universe, Galactic structure, and solar system. We show that the GTO and highly probable GO target list of exoplanets covers the Galactic disk/halo and high redshift universe, mostly well out of the plane of the disk of the Milky Way. Exposure times are of the order of the CEERS GTO medium-deep survey in a single filter, comparable to CANDELS in Hubble Space Telescope's surveys and deep fields. The area covered by NIRISS and NIRCam combined could accumulate to a half square degree surveyed.

Initial characterization of interstellar comet 2I/Borisov

Interstellar comets penetrating through the Solar System had been anticipated for decades. The discovery of asteroidal-looking 'Oumuamua was thus a huge surprise and a puzzle. Furthermore, the physical properties of the 'first scout' turned out to be impossible to reconcile with Solar System objects, challenging our view of interstellar minor bodies. Here, we report the identification and early characterization of a new interstellar object, which has an evidently cometary appearance. The body was discovered by Gennady Borisov on 30 August 2019 UT and subsequently identified as hyperbolic by our data mining code in publicly available astrometric data. The initial orbital solution implies a very high hyperbolic excess speed of ~32 km/s, consistent with 'Oumuamua and theoretical predictions. Images taken on 10 and 13 September 2019 UT with the William Herschel Telescope and Gemini North Telescope show an extended coma and a faint, broad tail. We measure a slightly reddish colour with a g'-r' colour index of 0.66 +/- 0.01 mag, compatible with Solar System comets. The observed morphology is also unremarkable and best explained by dust with a power-law size-distribution index of -3.7 +/- 1.8 and a low ejection speed (44 +/- 14 m/s for $\beta$ = 1 particles, where $\beta$ is the ratio of the solar gravitational attraction to the solar radiation pressure). The nucleus is probably ~1 km in radius, again a common value among Solar System comets, and has a negligible chance of experiencing rotational disruption. Based on these early characteristics, and putting its hyperbolic orbit aside, 2I/Borisov appears indistinguishable from the native Solar System comets.

Interpretation and diversity of exoplanetary material orbiting white dwarfs

ABSTRACT Nine metal-polluted white dwarfs are observed with medium-resolution optical spectroscopy, where photospheric abundances are determined and interpreted by comparison with Solar system objects. An improved method for making such comparisons is presented, which overcomes potential weaknesses of prior analyses, with numerous sources of error considered to highlight the limitations on interpretation. The stars are inferred to be accreting rocky, volatile-poor asteroidal materials with origins in differentiated bodies, in line with the consensus model. The most heavily polluted star in the sample has 14 metals detected, and appears to be accreting material from a rocky planetesimal, whose composition is mantle-like with a small Fe–Ni core component. Some unusual abundances are present. One star is strongly depleted in Ca, while two others show Na abundances elevated above bulk-Earth abundances; it is speculated that either the latter reflect diversity in the formation conditions of the source material, or they are traces of past accretion events. Another star shows clear signs that accretion ceased around 5 Myr ago, causing Mg to dominate the photospheric abundances, as it has the longest diffusion time of the observed elements. Observing such post-accretion systems allows constraints to be placed on models of the accretion process.

Database on detected stellar occultations by small outer Solar System objects

Observation of stellar occultation by objects of the Solar System is a powerful technique that allows measurements of size and shape of the small bodies with accuracies in the order of the kilometre. In addition, the occultation star probes the surroundings of the object, allowing the study of putative rings/debris or atmosphere around it. Since 2009, more than 60 events by trans-Neptunian and Centaur objects have been detected, involving more than 34 different bodies. Some remarkable results were achieved, such as the discovery of rings around Chariklo and Haumea, or the high albedo of Eris, the lack of global atmosphere around Makemake and the discovery of the double shape of 2014 MU69, among others. After the release of Gaia catalogues, predictions became more accurate, leading to an increasing number of successful observations of occultation events. To keep track of the results achieved with this technique, we created a database to gather all the detected events worldwide. The database is presented as an electronic table (http://occultations.ct.utfpr.edu.br/), where the main information obtained from any occultation by small outer solar system objects are listed. The structure and term definitions used in the database are presented here, as well as some simple statistics that can be done with the available results.

A TESS Search for Distant Solar System Planets: A Feasibility Study

As the NASA Transiting Exoplanet Survey Satellite (TESS) fulfills its primary mission it is executing an unprecedented all-sky survey with the potential to discover distant planets in our own solar system, as well as hundreds of Transneptunian Objects (TNOs) and Centaurs. We demonstrate that shift-and-stack techniques can be used to efficiently search the Full-Frame Image (FFI) data from the TESS mission and survey the entire sky for outer Solar System objects down to $\sim22^{nd}$ magnitude.

The population of rotational fission clusters inside asteroid collisional families

Asteroid families are groups of objects sharing similar orbits. They are mostly the results of past collisions between two asteroids. Recent studies have shown that some asteroid families can also be the outcome of the spin-up-induced fission of a critically rotating parent body (fission clusters). In at least four young fission clusters, more than 5% of their members belong to subfamilies, secondary clusters of objects mostly formed after the main fission event. However, asteroidal subfamilies are still not well characterized. In this work, using family recognition methods based on time-reversal dynamical simulations, machine-learning clustering algorithms and the exceptional orbit accuracy obtained from Gaia observations of Solar System objects, we identify several subclusters within four extremely young collisional families. We find that collisional asteroid families younger than 100 Myr have a higher fraction of young detectable fission subclusters with respect to older groups. The collisional events that form asteroid families may trigger a subsequent cascade of spin-induced formations of fission clusters by producing fragments in highly rotating states. Asteroid families created by collisions in the last ~100 Myr have a higher fraction of subfamilies than older ones. The impact produces highly rotating fragments that generate such subfamilies by fission and subsequently disperse. The final appearance of an asteroid family is thus the product of a drawn-out evolution.

What is Transiting HD 139139?

The NASA mission Kepler has detected 28 transits with depths and durations hours in the light curve of HD139139 during a 87 days campaign . Their arrival times are erratic. Rappaport et al. (2019) discard ten explanations. It is not clear if the transits are for HD 139139 or for a star B at 3.3 arcsec. New radial velocity variation data give RV for HD139139 in 4 days (F. Bouchy and S. Udry, private communication) excluding a close-in planet orbiting HD 139139, as proposed earlier (Schneider 2019). (However, this explanation is still valid for the star B for which radial velocity data are very poor). Here I thus explore new tentative explanations and their likelihood: 1/ An eccentric transiters belt around HD 139139 2/ Interstellar transiters 3/ Solar System objects.

Phase Curves from the Kuiper Belt: Photometric Properties of Distant Kuiper Belt Objects Observed by New Horizons

Abstract Prior to its close encounter with the Kuiper Belt object (KBO) (486958) 2014 MU69 on 2019 January 1, NASA’s New Horizons spacecraft observed other KBOs from distances greater than 0.1 au at solar phase angles far larger than those attainable from Earth. The expanded range in phase angle afforded by these distant KBO (DKBO) observations enables comparisons between their phase functions and those of other solar system objects. Here we present extended New Horizons phase angle coverage of plutino (15810) Arawn (1994 JR1) to 131°, resonant KBO 2012 HE85 to 64°, scattered disk KBO 2011 HK103 to 124°, hot classical (515977) 2012 HZ84 to 73°, and cold classical KBOs 2011 HJ103 and 2011 JY31 to 27° and 122°, respectively. In general, DKBO solar phase curves have slopes (i.e., phase coefficients) and shapes (with corresponding phase integrals q) similar to those of other dark, small solar system objects including comet nuclei, asteroids, and satellites. Until stellar occultations by these DKBOs provide information about their size, geometric albedos p (and Bond albedos A = pq) must be inferred from the median albedos measured by thermal radiometry for each dynamical class. Bond albedos for these DKBOs range from 0.01 to 0.04. Cold classical JY31 has a slightly lower slope and higher phase integral than the other DKBOs, and its slope and phase integral come closest to matching those of cold classical MU69, suggesting that cold classical KBOs share surface scattering characteristics that are distinct from those of other KBOs.

Elemental and molecular abundances in comet 67P/Churyumov-Gerasimenko

ABSTRACTComets are considered to be some of the most pristine and unprocessed Solar system objects accessible to in situ exploration. Investigating their molecular and elemental composition takes us on a journey back to the early period of our Solar system and possibly even further. In this work, we deduce the bulk abundances of the major volatile species in comet 67P/Churyumov-Gerasimenko, the target of the European Space Agency’s (ESA) Rosetta mission. The basis are measurements obtained with the ROSINA instrument suite on board the Rosetta orbiter during a suitable period of high outgassing near perihelion. The results are combined with both gas and dust composition measurements published in the literature. This provides an integrated inventory of the major elements present in the nucleus of 67P/Churyumov-Gerasimenko. Similar to comet 1P/Halley, which was visited by ESA’s Giotto spacecraft in 1986, comet 67P/Churyumov-Gerasimenko also shows near-solar abundances of oxygen and carbon, whereas hydrogen and nitrogen are depleted compared to solar. Still, the degree of devolatilization is lower than that of inner Solar system objects, including meteorites and the Earth. This supports the idea that comets are amongst the most pristine objects in our Solar system.

Multidimensional scaling analysis of the solar system objects

In this paper, we analyse the attributes of some well-known objects in the solar system using clustering methods. Objects such as planets (with/without an estimate of Planet Nine), dwarf planets and some candidates for dwarf planets are considered. Different distances such as the Canberra, Jaccard, Lorentzian and Manhattan are adopted to calculate the relations between all objects based on their characteristics. The high dimensional information can thus be represented in a smaller number of dimensions via the maps generated by the hierarchical clustering and multidimensional scaling. The numerical measures and the computational tools allow the visualization of the solar system objects in a locus reflecting their characteristics.

Apse-alignment in narrow-eccentric ringlets and its implications for the ϵ-ring of Uranus and the ring system of (10199) Chariklo

The discovery of ring systems around objects of the outer Solar System provides a strong motivation to apply theoretical models in order to better estimate their physical and orbital parameters, which can constrain scenarios for their origin.We review the criterion for maintaining apse-alignment across a ring and the balance between the energy input rate provided by a close by satellite and the internal dissipation rate occurring through ring particle collisions that is required to maintain ring eccentricity, as derived from the equations of motion governing the Lagrangian-displacements of the ring-particle orbits. We use the case of the ϵ-ring of Uranus, to calibrate our theoretical discussion and illustrate the basic dynamics governing these types of ring.In the case of the ring system of (10199) Chariklo, where the evidence that the rings are eccentric is not conclusive, we apply the theory of apse-alignment to derive information about the most plausible combination of values of the surface density and eccentricity-gradient, as well as the masses and locations of their postulated but - presently undetected - shepherd-satellites.When the balance conditions that we predict are applied to the ring system of (10199) Chariklo, we are able to estimate the minimum mass of a shepherd satellite required to prevent eccentricity decay, as a function of its orbital location, for two different models of dissipation. We conclude that the satellite mass required to maintain the m = 1 eccentric mode in the ring, would be similar or smaller than that needed to confine the rings radially.Our estimation of the most plausible combinations of eccentricity gradient and surface density consistent with apse-alignment are based on a standard model for the radial form of the surface density distribution, which approximately agrees with the optical depth profile derived by the stellar occultations. We find a diverse range of solutions, with combinations of eccentricity gradient and surface mass density that tend to minimize required enhanced collisional effects, having adopted estimated values of the form factor of the second degree harmonic of the gravitational potential.

Fluidized Appearing Ejecta on Ceres: Implications for the Mechanical Properties, Frictional Properties, and Composition of its Shallow Subsurface

AbstractSeveral ejecta deposits on Ceres display morphological characteristics not commonly associated with dry ballistic emplacement. We characterized 30 examples of fluidized appearing ejecta (FAE) on Ceres and identified two distinct morphological populations: cuspate/lobate FAE and channelized FAE. The cuspate/lobate FAE typically display one or more of the following characteristics: well‐defined margins, a sheeted or layered appearance, arcuate or cuspate terminal lobes, and occasional mass concentrations at their distal margins. The channelized FAE typically display a morphology dominated by topographically focused channelized flows and arcuate terminal lobes but lack the well‐defined margins common among their cuspate/lobate counterparts. Although Cerean FAE are holistically distinct from rampart/layered ejecta craters on Mars, Ganymede, and other icy solar system objects, many of their aforementioned morphological characteristics are commonly found among these other examples of fluidized ejecta. The formation of Martian and icy satellite fluidized ejecta has been widely attributed to the mobilization of near‐surface volatiles, namely, water ice. The documented Cerean FAE are observed between absolute latitudes of 70°, with a slight enrichment in the midlatitudes of the southern hemisphere. We test the hypothesis that the morphologies and mobilities of Cerean FAE can be explained via impacting into a low‐cohesion ice‐silicate target material, followed by material sliding on a low‐friction partially icy substrate. We do this by comparing the observed Cerean FAE to a kinematic‐dynamic sliding ejecta emplacement model. We find that a mechanically weak, H2O‐rich near‐surface layer is consistent with the range of ejecta mobilities and morphologies observed in this investigation.

Experimenting with Mixtures of Water Ice and Dust as Analogues for Icy Planetary Material

Due to its abundance and unique properties, water is a major actor in the formation and evolution of many planetary surfaces as well as a sensitive and reliable tracer of past geologic and climatic processes. Water ice is found in variable abundance at the surfaces of many Solar System objects, from the floor of permanently shadowed craters at the poles of Mercury to large fractions of the surfaces of several trans-Neptunian objects. With few exceptions, water is not found in pure form but associated to contaminants of various nature and concentration. These associations and the nature of the mixing and segregation processes that affect and control them are key for our understanding of some of the most important aspects of planetary evolution processes. The observation and characterization of water ice at the surface of Solar System objects is therefore among the primary scientific objectives of many space missions. The quantitative interpretation of remote sensing data in terms of surface composition and physical properties requires the use of complex physical models that rely on experimental data in two different ways. First, the models require as inputs the fundamental properties of the pure materials, such as the optical or dielectric constant. Second, the models can only be fully tested if their results are confronted to actual measurements performed on samples whose complexity comes close to the one encountered on natural planetary surfaces but which are nevertheless well-enough characterized to serve as reference. Such measurements are challenging as macroscopic ice-rich samples prepared as analogues of icy planetary surfaces tend to be unstable, the ice component being prone to metamorphism and phase change. The questions of the reproducibility of the samples and the relevance of the measurements are therefore critical. The Ice Laboratory at the University of Bern has been set up in 2010 to overcome some of these difficulties. We have developed protocols to prepare, store, handle and characterize various associations of ice with mineral and organics contaminants as analogues of different types of icy Solar System surfaces. The aims of this article are to present the context and background for our investigations, describe these protocols and associated hardware in a comprehensive way, provide quantitative characterization of the samples obtained using these protocols and summarize the main results obtained so far by experimenting with these samples. The current state and possible future evolutions of this project are then discussed in the context of the next generation of space missions to visit icy objects in the Solar System and longer term perspectives on future observations of protoplanetary discs and exoplanetary systems.

The ssos pipeline: Identification of Solar System objects in astronomical images

Observatories and satellites around the globe produce tremendous amounts of imaging data to study many different astrophysical phenomena. The serendipitous observations of Solar System objects are a fortunate by-product which have often been neglected due to the lack of a simple yet efficient identification algorithm. Meanwhile, the determination of the orbit, chemical composition, and physical properties such as rotation period and 3D-shape of Solar System objects requires a large number of astrometry and multi-band photometry observations. Such observations are hidden in current and future astrophysical archives, and a method to harvest these goldmines is needed. This article presents an easy-to-implement, light-weight software package which detects bodies of the Solar System in astronomical images and measures their astrometry and photometry. The ssos pipeline is versatile, allowing for application to all kinds of observatory imaging products. The sole principle requirement is that the images observe overlapping areas of the sky within a reasonable time range. Both known and unknown Solar System objects are recovered, from fast-moving near-Earth asteroids to slow objects in the Kuiper belt. The high-level pipeline design and two test applications are described here, highlighting the versatility of the algorithm with both narrow-field pointed and wide-field survey observations. In the first study, 2,828 detections of 204 SSOs are recovered from publicly available images of the GTC OSIRIS Broad Band DR1. The false-positive ratio of SSO detections ranges from 0%-23% depending on the pipeline setup. The second test study utilizes the images of the first data release of J-PLUS, a 12-band optical survey. 4,606 SSO candidates are recovered, with a false-positive ratio of (2.0 +- 0.2)%.

The Zwicky Transient Facility: Science Objectives

The Zwicky Transient Facility (ZTF), a public–private enterprise, is a new time-domain survey employing a dedicated camera on the Palomar 48-inch Schmidt telescope with a 47 deg2 field of view and an 8 second readout time. It is well positioned in the development of time-domain astronomy, offering operations at 10% of the scale and style of the Large Synoptic Survey Telescope (LSST) with a single 1-m class survey telescope. The public surveys will cover the observable northern sky every three nights in g and r filters and the visible Galactic plane every night in g and r. Alerts generated by these surveys are sent in real time to brokers. A consortium of universities that provided funding (“partnership”) are undertaking several boutique surveys. The combination of these surveys producing one million alerts per night allows for exploration of transient and variable astrophysical phenomena brighter than r ∼ 20.5 on timescales of minutes to years. We describe the primary science objectives driving ZTF, including the physics of supernovae and relativistic explosions, multi-messenger astrophysics, supernova cosmology, active galactic nuclei, and tidal disruption events, stellar variability, and solar system objects.

The v2 = 1, 2 and v4 = 1 bending states of 15NH3 and their analysis at experimental accuracy.

15NH3 is the object of extensive investigation due to the central role of ammonia in astronomical sciences and to the complexity of modeling its interacting vibrationally excited states. Of major interest in astrochemistry is the determination of the 14N/15N ratio in space, characterized by unexpected variability among different solar system objects and reservoirs. Recently, the spectroscopic analysis of ground and v2 = 1 a, s states of 15NH3 has been completed at experimental accuracy. Here, the characterization of the a, s inversion symmetry levels of v2 = 1, 2 and v4 = 1 states is presented. New spectra of 15NH3 have been recorded from 325 to 2000 cm-1 at a resolution ranging from 0.00096 cm-1 to 0.003 cm-1, using the Canadian Light Source synchrotron at CLS. 7518 transitions covering nine bands, ν2, 2ν2, ν4, 2ν2 ← ν2, ν4 ← ν2, 2ν2 ↔ ν4 and the inversion-rotation transitions in the excited states, have been fitted simultaneously. The effective Hamiltonian adopted includes all symmetry allowed interactions between and within the studied excited states, according to the most recent results on ammonia. The transitions have been reproduced at experimental accuracy using 185 spectroscopic parameters, determined with high precision. The leading diagonal parameters, Gv, B, C, D's, compare well with those of 14NH3. The wavenumbers of the assigned transitions are compared with their theoretically predicted values. An improved set of ground state parameters is also derived. These results noticeably improve the wavenumber line list in the high-resolution transmission molecular absorption (HITRAN) database.