A giant collision is believed to be at the origin of the Pluto-Charon system. As a result, the initial orbit and spins after impact may have substantially differed from those observed today. More precisely, the distance at periapse may have been shorter, subsequently expanding to its current separation by tides raised simultaneously on the two bodies. Here we provide a general 3D model to study the tidal evolution of a binary composed of two triaxial bodies orbiting a central star. We apply this model to the Pluto-Charon binary, and notice some interesting constraints on the initial system. We observe that when the eccentricity evolves to high values, the presence of the Sun prevents Charon from escaping because of Lidov-Kozai cycles. However, for a high initial obliquity for Pluto or a spin-orbit capture of Charon's rotation, the binary eccentricity is damped very efficiently. As a result, the system can maintain a moderate eccentricity throughout its evolution, even for strong tidal dissipation on Pluto.
Pluto has been observed by the New Horizons space probe to have some relatively fresh ice on the old ices covering most of the surface. Pluto was thought to consist of only a rocky core below the ice. Here I show that Pluto can have an iron core, as can also its companion Charon, which has recently been modelled to have one. The presence of an iron core means the giant impact origin calculations should be redone to include iron and thus higher temperatures. An iron core leads to the possibility of a different geology. An originally molten core becomes solid later, with contraction and a releas…
Current theory considers two options for the formation of the Pluto-Charon binary (Canup 2005, 2011; Desch 2015). In the `hit-and-run' model, a lower mass projectile barely hits the more massive Pluto, kicks up some debris, and remains bound to Pluto (see also Asphaug et al. 2006). In a `graze-and-merge' scenario, the projectile ejects substantial debris as it merges with Pluto (see also Canup 2001). To investigate the graze-and-merge idea in more detail, we consider the growth of Charon-mass objects within a circum-Pluto ring of solids. Numerical calculations demonstrate that Charon analogs f…
The Pluto-Charon system, likely formed from an impact, has reached the endpoint of its tidal evolution. During its evolution into the dual-synchronous state, the equilibrium tidal figures of Pluto and Charon would have also evolved as angular momentum was transferred from Pluto's spin to Charon's orbit. The rate of tidal evolution is controlled by Pluto's interior physical and thermal state. We examine three interior models for Pluto: an undifferentiated rock/ice mixture, differentiated with ice above rock, and differentiated with an ocean. For the undifferentiated case without an ocean, the P…
Existence of subsurface oceans on the satellites of the giant planets and Trans-Neptunian objects has been predicted for some time. Oceans on icy worlds exert a considerable influence on the dynamics of the ice-ocean system and, because of the astrobiological potential, represent an important objective for future missions. The Pluto-Charon system is representative of an icy moon orbiting a dwarf planet formed from the remnants of a giant impact. Evolution of icy moons is primarily controlled by the mode and efficiency of heat transfer through the outer ice shell, which is influenced by the pre…
This paper explores the possibility that the progenitors of the small satellites of Pluto got captured in the Pluto-Charon system from the massive heliocentric planetesimal disk in which Pluto was originally embedded into. We find that, if the dynamical excitation of the disk is small, temporary capture in the Pluto-Charon system can occur with non-negligible probability, due to the dynamical perturbations exerted by the binary nature of the Pluto-Charon pair. However, the captured objects remain on very elliptic orbits and the typical capture time is only 100 years. In order to explain the or…
The exploration of the Pluto-Charon system by the New Horizons spacecraft represents the first opportunity to understand the distribution of albedo and other photometric properties of the surfaces of objects in the Solar System's "Third Zone" of distant ice-rich bodies. Images of the entire illuminated surface of Pluto and Charon obtained by the Long Range Reconnaissance Imager (LORRI) camera provide a global map of Pluto that reveals surface albedo variegations larger than any other Solar System world except for Saturn's moon Iapetus. Normal reflectances on Pluto range from 0.08-1.0, and the …
Using a suite of numerical calculations, we consider the long-term evolution of circumbinary debris from the Pluto-Charon giant impact. Initially, these solids have large eccentricity and pericenters near Charon's orbit. On time scales of 100-1000 yr, dynamical interactions with Pluto and Charon lead to the ejection of most solids from the system. As the dynamics moves particles away from the barycenter, collisional damping reduces the orbital eccentricity of many particles. These solids populate a circumbinary disk in the Pluto-Charon orbital plane; a large fraction of this material lies with…
Approach images taken by the LORRI imaging system during the New Horizons spacecraft encounter have been used to determine the mean radii and shapes of Pluto and Charon. The primary observations are limb locations derived using three independent approaches. The resulting mean radii of Pluto and Charon are 1188.3 +/- 1.6 km and 606.0 +/- 1.0 km, respectively (2-sigma). The corresponding densities are 1854 +/- 11 kg m-3 and 1701 +/- 33 kg m-3 (2-sigma). The Charon radius value is consistent with previous Earth-based occultation estimates. The Pluto radius estimate is consistent with solar occult…
Pluto and its five known satellites form a complex dynamic system. Here we explore where additional satellites could exist exterior to Charon (the innermost moon) but interior of Hydra (the outermost). We also provide dynamical constraints for the masses of the known satellites. We show that there are significant stable regions interior of Styx and between Nix and Kerberos. In addition, we show that coorbitals of the known small satellites are stable, even at high inclinations, and discuss mass constraints on undiscovered satellites in such orbits.
Pluto's terrains display a diversity of crater retention ages ranging from areas with no identifiable craters to heavily cratered terrains. This variation in crater densities is consistent with geologic activity occurring throughout Pluto's history and also a variety of resurfacing styles, including both exogenic and endogenic processes. Using estimates of impact flux and cratering rates over time, Pluto's heavily cratered terrains appear to be relatively ancient, 4 Ga or older. Charon's smooth plains, informally named Vulcan Planitia, did experience early resurfacing, but there is a relativel…
We consider a scenario where the small satellites of Pluto and Charon grew within a disk of debris from an impact between Charon and a trans-Neptunian Object (TNO). After Charon's orbital motion boosts the debris into a disk-like structure, rapid orbital damping of meter-size or smaller objects is essential to prevent the subsequent re-accretion or dynamical ejection by the binary. From analytical estimates and simulations of disk evolution, we estimate an impactor radius of 30-100 km; smaller (larger) radii apply to an oblique (direct) impact. Although collisions between large TNOs and Charon…
The Pluto-Charon binary system is the best-studied representative of the binary Kuiper-belt population. Its origins are vital to understanding the formation of other Kupier-belt objects (KBO) and binaries, and the evolution of the outer solar-system. The Pluto-Charon system is believed to form following a giant impact between two massive KBOs at relatively low velocities. However, the likelihood of a random direct collision between two of the most massive KBOs is low, and is further constrained by the requirement of a low-velocity collision, making this a potentially fine-tuned scenario. Here …
The space probe 'New Horizon' was launched on 19th of January 2006 in order to study Pluto and its moons. Spacecraft will fly by Pluto as close as 12500 km in the middle of July 2015 and will get the most detailed images of Pluto and its moon until this moment. At the same time, observation obtained by the ground-based telescopes may also be helpful for the research of such distant system. Thereby, the Laboratory of observational astrometry of Pulkovo Observatory of RAS made a decision to reprocess observations obtained during last decade. More than 350 positional observations of Pluto - Charo…
During 2005-2012, images from Hubble Space Telescope (HST) revealed four moons orbiting Pluto-Charon (Weaver et al 2006, Showalter et al 2011, 2012). Although their orbits and geometric shapes are well-known, the 2$σ$ uncertainties in the masses of the two largest satellites - Nix and Hydra - are comparable to their HST masses (Brozovic et al 2015, Showalter & Hamilton 2015, Weaver et al 2016). Remarkably, gravitational $n$-body computer calculations of the long-term system stability on 0.1-1 Gyr time scales place much tighter constraints on the masses of Nix and Hydra, with upper limits $\sim…
Pluto's system of 5 known satellites are in a puzzling orbital configuration. Each of the four small satellites are on low-eccentricity and low-inclination orbits situated near a mean motion resonance with the largest satellite Charon. The Pluto-Charon binary likely formed as a result of a giant impact and so the simplest explanation for the small satellites is that they accreted from debris of that collision. The Pluto-Charon binary has evolved outward since its formation due to tidal forces, which drove them into their current doubly synchronous state. Meanwhile, leftover debris from the for…
In this letter we explore the environment of Pluto and Charon in the far infrared with the main aim to identify the signs of any possible dust ring, should it exist in the system. Our study is based on observations performed at 70 um with the PACS instrument onboard the Herschel Space Observatory at 9 epochs between March 14 and 19, 2012. The far-infrared images of the Pluto-Charon system are compared to those of the point spread function (PSF) reference quasar 3C454.3. The deviation between the observed Pluto-Charon and reference PSFs are less then 1 sigma indicating that clear evidence for a…
We study the impactor flux and cratering on Pluto and Charon due to the collisional evolution of Plutinos. Plutinos are those trans-Neptunian objects located at 39.5 AU, in the 3:2 mean motion resonance with Neptune. To do this, we develop a statistical code that includes catastrophic collisions and cratering events, and takes into account the stability and instability zones of the 3:2 mean motion resonance with Neptune. We proposes different initial populations that account for the uncertainty in the size distribution of Plutinos at small sizes. Depending on the initial population, our result…
In this paper, the near-optimal capture problem is numerically investigated to locate the optimal capture points around Charon using the Pluto-Charon planar circular restricted three-body problem (PCRTBP). Capture orbits are divided into the pre- and post-maneuver portions. In the pre-maneuver portion, the gravitational capture conditions are discussed by backward numerical integration. In the post-maneuver portion, the smaller alignment index (SALI) is applied to numerically investigate the orbital characters of long-term capture orbits around Charon. The initial conditions corresponding to t…
Both Pluto and its satellite Charon have rotation rates synchronous with their orbital mean motion. This is the theoretical end point of tidal evolution where transfer of angular momentum has ceased. Here we follow Pluto's tidal evolution from an initial state having the current total angular momentum of the system but with Charon in an eccentric orbit with semimajor axis $a \approx 4R_P$ (where $R_P$ is the radius of Pluto), consistent with its impact origin. Two tidal models are used, where the tidal dissipation function $Q \propto$ 1/frequency and $Q=$ constant, where details of the evoluti…
The Pluto-Charon system has come into sharper focus following the fly by of New Horizons. We use N-body simulations to probe the unique dynamical history of this binary dwarf planet system. We follow the evolution of the debris disc that might have formed during the Charon-forming giant impact. First, we note that in-situ formation of the four circumbinary moons is extremely difficult if Charon undergoes eccentric tidal evolution. We track collisions of disc debris with Charon, estimating that hundreds to hundreds of thousands of visible craters might arise from 0.3--5 km radius bodies. New Ho…
New Horizons mission observations show that the small satellites Styx, Nix, Kerberos and Hydra, of the Pluto-Charon system, have not tidally spun-down to near synchronous spin states and have high obliquities with respect to their orbit about the Pluto-Charon binary (Weaver et al. 2016). We use a damped mass-spring model within an N-body simulation to study spin and obliquity evolution for single spinning non-round bodies in circumbinary orbit. Simulations with tidal dissipation alone do not show strong obliquity variations from tidally induced spin-orbit resonance crossing and this we attribu…
The New Horizons spacecraft mapped colors and infrared spectra across the encounter hemispheres of Pluto and Charon. The volatile ices CH$_4$, CO, and N$_2$, that dominate Pluto's surface, have complicated spatial distributions resulting from sublimation, condensation, and glacial flow acting over seasonal and geological timescales. Pluto's H$_2$O ice "bedrock" is also mapped, with isolated outcrops occurring in a variety of settings. Pluto's surface exhibits complex regional color diversity associated with its distinct provinces. Charon's color pattern is simpler, dominated by neutral low lat…
The flyby of Pluto and Charon by the New Horizons spacecraft provided high-resolution images of cratered surfaces embedded in the Kuiper belt, an extensive region of bodies orbiting beyond Neptune. Impact craters on Pluto and Charon were formed by collisions with other Kuiper belt objects (KBOs) with diameters from ~40 kilometers to ~300 meters, smaller than most KBOs observed directly by telescopes. We find a relative paucity of small craters less than approximately 13 kilometers in diameter, which cannot be explained solely by geological resurfacing. This implies a deficit of small KBOs (les…
The orbits of Pluto's four small satellites (Styx, Nix, Kerberos, and Hydra) are nearly circular and coplanar with the orbit of the large satellite Charon, with orbital periods nearly in the ratios 3:1, 4:1, 5:1, and 6:1 with Charon's orbital period. These properties suggest that the small satellites were created during the same impact event that placed Charon in orbit and had been pushed to their current positions by being locked in mean-motion resonances with Charon as Charon's orbit was expanded by tidal interactions with Pluto. Using the Pluto-Charon tidal evolution models developed by Che…
Four small moons (Styx, Nix, Kerberos and Hydra) are at present known to orbit around the barycenter of Pluto and Charon, which are themselves considered a binary dwarf-planet due to their relatively high mass ratio. The central, non-axisymmetric potential induces moon orbits inconvenient to be described by Keplerian osculating elements. Here, we report that observed orbital variations, may not be the result of orbital eccentricities or observational uncertainties, but may be due to forced oscillations caused by the central binary. We show, using numerical integration and analytical considerat…
We consider the formation of satellites around the Pluto-Charon binary. An early collision between the two partners likely produced the binary and a narrow ring of debris, out of which arose the moons Styx, Nix, Kerberos and Hydra. How the satellites emerged from the compact ring is uncertain. Here we show that a particle ring spreads from physical collisions and collective gravitational scattering, similar to migration. Around a binary, these processes take place in the reference frames of "most circular" orbits, akin to circular ones in a Keplerian potential. Ring particles damp to these orb…
We numerically investigate the orbital dynamics of a spacecraft, or a comet, or an asteroid in the Pluto-Charon system in a scattering region around Charon using the planar circular restricted three-body problem. The test particle can move in bounded orbits around Charon or escape through the necks around the Lagrangian points $L_1$ and $L_2$ or even collide with the surface of Charon. We explore four of the five possible Hill's regions configurations depending on the value of the Jacobi constant which is of course related with the total orbital energy. We conduct a thorough numerical analysis…
A unique feature of Pluto's large satellite Charon is its dark red northern polar cap. Similar colours on Pluto's surface have been attributed to organic macromolecules produced by energetic radiation processing of hydrocarbons. The polar location of this material on Charon implicates the temperature extremes that result from Charon's high obliquity and long seasons. The escape of Pluto's atmosphere provides a potential feed stock for production of complex chemistry. Gas from Pluto that is transiently cold-trapped and processed at Charon's winter pole was proposed as an explanation on the basi…
Synchronisation of a tidal binary by inward orbital migration. The case of Pluto and Charon
US Naval Observatory（美国海军天文台）；Charles University（查理大学）；King Abdullah University of Science and Technology（阿卜杜拉国王科技大学）；California Institute of Technology（加州理工学院）；ETH Zürich（苏黎世联邦理工学院）
The small satellites of the Pluto system (Styx, Nix, Kerberos, and Hydra) have very low surface escape velocities, and impacts should therefore eject a large amount of material from their surfaces. We show that most of this material then escapes from the Pluto system, though a significant fraction collects on the surfaces of Pluto and Charon. The velocity at which the dust is ejected from the surfaces of the small satellites strongly determines which object it is likely to hit, and where on the surfaces of Pluto and Charon it is most likely to impact. We also show that the presence of an atmos…
NASA's New Horizons spacecraft has revealed the complex geology of Pluto and Charon. Pluto's encounter hemisphere shows ongoing surface geological activity centered on a vast basin containing a thick layer of volatile ices that appears to be involved in convection and advection, with a crater retention age no greater than $\approx$10 Ma. Surrounding terrains show active glacial flow, apparent transport and rotation of large buoyant water-ice crustal blocks, and pitting, likely by sublimation erosion and/or collapse. More enigmatic features include tall mounds with central depressions that are …
A search for temporal changes on Pluto and Charon was motivated by (1) the discovery of young surfaces in the Pluto system that imply ongoing or recent geologic activity, (2) the detection of active plumes on Triton during the Voyager 2 flyby, and (3) the abundant and detailed information that observing geologic processes in action provides about the processes. A thorough search for temporal changes using New Horizons images was completed. Images that covered the same region were blinked and manually inspected for any differences in appearance. The search included full-disk images such that al…
Context. The orbits of the four small moons in the Pluto-Charon system, Styx, Nix, Kerberos and Hydra, are circumbinary, as the former form a binary dwarf planet. Consequently, the orbit of each one of them is characterized by a number of frequencies, arising by the central binary and the mutual gravitational interactions. Aims. In this work, we identify the most prominent of these forced frequencies using Fast Fourier Transformations. Methods. Two methods are implemented, a semi-analytic and a numerical one, and comparisons are being made. Results. The results indicate that as a first approxi…
Thermal observations of the Pluto-Charon system acquired by the Herschel Space Observatory in February 2012 are presented. They consist of photometric measurements with the PACS and SPIRE instruments (nine visits to the Pluto system each), covering six wavelengths from 70 to 500 $μ$m altogether. The thermal light curve of Pluto-Charon is observed in all filters, albeit more marginally at 160 and especially 500 $μ$m. Putting these data into the context of older ISO, Spitzer and ground-based observations indicates that the brightness temperature (T$_B$) of the system (rescaled to a common helioc…
The formation of Pluto's small satellites - Styx, Nix, Keberos and Hydra - remains a mystery. Their orbits are nearly circular and are near mean-motion resonances and nearly coplanar with Charon's orbit. One scenario suggests that they all formed close to their current locations from a disk of debris that was ejected from the Charon-forming impact before the tidal evolution of Charon. The validity of this scenario is tested by performing $N$-body simulations with the small satellites treated as test particles and Pluto-Charon evolving tidally from an initial orbit at a few Pluto radii with ini…
Using a large suite of n-body simulations, we explore the discovery space for new satellites in the Pluto-Charon system. For the adopted masses and orbits of the known satellites, there are few stable prograde or polar orbits with semimajor axes $a \lesssim 1.1~a_H$, where $a_H$ is the semimajor axis of the outermost moon Hydra. Small moons with radii $r \lesssim$ 2 km and $a \lesssim 1.1~a_H$ are ejected on time scales ranging from several yr to more than 10 Myr. Orbits with $a \gtrsim 1.1~a_H$ are stable on time scales exceeding 100 Myr. Near-IR and mid-IR imaging with JWST and ground-based …
We investigate the resonant rotation of circumbinary bodies in planar quasi-circular orbits. Denoting $n_b$ and $n$ the orbital mean motion of the inner binary and of the circumbinary body, respectively, we show that spin-orbit resonances exist at the frequencies $n\pm kν/2$, where $ν= n_b - n$, and $k$ is an integer. Moreover, when the libration at natural frequency has the same magnitude as $ν$, the resonances overlap and the rotation becomes chaotic. We apply these results to the small satellites in the Pluto-Charon system, and conclude that their rotations are likely chaotic. However, the …
During its departure from Pluto, New Horizons used its LORRI camera to image a portion of Pluto's southern hemisphere that was in a decades-long seasonal winter darkness, but still very faintly illuminated by sunlight reflected by Charon. Recovery of this faint signal was technically challenging. The bright ring of sunlight forward-scattered by haze in the Plutonian atmosphere encircling the nightside hemisphere was severely overexposed, defeating the standard smeared-charge removal required for LORRI images. Reconstruction of the overexposed portions of the raw images, however, allowed adequa…
The Pluto-Charon (PC) pair is usually thought of as a binary in the dual synchronous state, which is the endpoint of its tidal evolution. The discovery of the small circumbinary moons, Styx, Nix, Kerberos, and Hydra, placed close to the mean motions resonances (MMRs) 3/1, 4/1, 5/1, and 6/1 with Charon, respectively, reveals a complex dynamical architecture of the system. Several formation mechanisms for the PC system have been proposed. Our goal is to analyse the past and current orbital dynamics of the satellite system. We study the past and current dynamics of the PC system through a large s…
We searched for dust or debris rings in the Pluto-Charon system before, during, and after the New Horizons encounter. Methodologies included searching for back-scattered light during the approach to Pluto (phase $\sim15^\circ$), in situ detection of impacting particles, a search for stellar occultations near the time of closest approach, and by forward-scattered light during departure (phase $\sim165^\circ$). A search using HST prior to the encounter also contributed to the results. No rings, debris, or dust features were observed, but our detection limits provide an improved picture of the en…
The dwarf planet Pluto is known to host an extended system of five co-planar satellites. Previous studies have explored the formation and evolution of the system in isolation, neglecting perturbative effects by the Sun. Here we show that secular evolution due to the Sun can strongly affect the evolution of outer satellites and rings in the system, if such exist. Although precession due to extended gravitational potential from the inner Pluto-Charon binary quench such secular evolution up to $a_{crit}\sim0.0035$ AU ($\sim0.09$ $R_{Hill}$ the Hill radius; including all of the currently known sat…
Systematic geomorphological mapping and detailed landform analysis using the highest resolution images obtained by the New Horizons spacecraft reveal the presence of a range of differentiable terrains on Charon, the largest moon of Pluto, that were not examined in detail by the early studies. The most important findings of our work include (1) truncation and omission of large craters (diameters > 30-40 km) and their crater rim ridges along the eastern edges of several north-trending, eastward-convex, arcuate ranges in Oz Terra, (2) lobate ridges, lobate knob trains, and lobate aprons resemblin…
Planets and satellites orbiting a binary system exist in the solar system and extrasolar planetary systems. Their orbits can be significantly different from Keplerian orbits, if they are close to the binary and the secondary-to-primary mass ratio is high. A proper description of a circumbinary orbit is in terms of the free eccentricity $e_{\rm free}$ at the epicyclic frequency $κ_0$, forced eccentricity $e_{\rm forced}$ at the mean motion $n_0$, and oscillations at higher frequencies forced by the non-axisymmetric components of the binary's potential. We show that accurate numerical values for…
Observations of Pluto's companion planet Charon have so far yielded no compelling evidence for a persistent atmosphere. However, with the upcoming encounter of New Horizons at the Pluto-Charon system, sensitivity to detection of a possible Charon atmosphere will increase by orders of magnitude. In particular, it has long been planned for New Horizons to use its Alice ultraviolet spectrograph during solar occultation observations of Charon on July 14, 2015, for this purpose. But in the days before closest encounter, the Alice instrument will also acquire spectra of reflected sunlight from Charo…
We discuss a new set of $\sim$ 500 numerical n-body calculations designed to constrain the masses and bulk densities of Styx, Nix, Kerberos, and Hydra. Comparisons of different techniques for deriving the semimajor axis and eccentricity of the four satellites favor methods relying on the theory of Lee & Peale (2006), where satellite orbits are derived in the context of the restricted three body problem (Pluto, Charon, and one massless satellite). In each simulation, we adopt the nominal satellite masses derived in Kenyon & Bromley (2019a), multiply the mass of at least one satellite by a numer…
Using the Andrade-derived Sundberg-Cooper rheology, we apply several improvements to the secular tidal evolution of TRAPPIST-1e and the early history of Pluto-Charon under the simplifying assumption of homogeneous bodies. By including higher-order eccentricity terms (up to and including $e^{20}$), we find divergences from the traditionally used $e^{2}$ truncation starting around $e=0.1$. Order-of-magnitude differences begin to occur for $e>0.6$. Critically, higher-order eccentricity terms activate additional spin-orbit resonances. Worlds experiencing non-synchronous rotation can fall into and …
The Pluto system provides a unique local laboratory for the study of binaries with multiple low mass companions. In this paper, we study the orbital stability of P4, the most recently discovered moon in the Pluto system. This newfound companion orbits near the plane of the Pluto-Charon binary, roughly halfway between the two minor moons Nix and Hydra. We use a suite of few body integrations to constrain the masses of Nix and Hydra, and the orbital parameters of P4. For the system to remain stable over the age of the Solar System, the masses of Nix and Hydra likely do not exceed 5e16 kg and 9e1…
The Pluto-Charon system provides a broad variety of constraints on planetary formation, composition, chemistry, and evolution. Pluto was the first body to be discovered in what is now known as the Kuiper belt, its orbit ultimately becoming a major clue that the giant planets underwent substantial orbital migration early in Solar System history. This migration has been linked to an early instability in the orbits of the giant planets and the formation of the Kuiper belt itself, from an ancestral trans-Neptunian planetesimal disk that included Pluto. Pluto-Charon is emblematic of what are now re…
Motivated by the New Horizons mission, we consider how Pluto's small satellites -- currently Styx, Nix, Kerberos, and Hydra -- grow in debris from the giant impact that forms the Pluto-Charon binary. After the impact, Pluto and Charon accrete some of the debris and eject the rest from the binary orbit. During the ejection, high velocity collisions among debris particles produce a collisional cascade, leading to the ejection of some debris from the system and enabling the remaining debris particles to find stable orbits around the binary. Our numerical simulations of coagulation and migration s…
In 2015, the New Horizons spacecraft flew past Pluto and its moon Charon, providing the first clear look at the surface of Charon. New Horizons images revealed an ancient surface, a large, intricate canyon system, and many fractures, among other geologic features. Here, we assess whether tidal stresses played a significant role in the formation of tensile fractures on Charon. Although presently in a circular orbit, most scenarios for the orbital evolution of Charon include an eccentric orbit for some period of time and possibly an internal ocean. Past work has shown that these conditions could…
The goal of this chapter is to review hypotheses for the origin of the Pluto system in light of observational constraints that have been considerably refined over the 85-year interval between the discovery of Pluto and its exploration by spacecraft. We focus on the giant impact hypothesis currently understood as the likeliest origin for the Pluto-Charon binary, and devote particular attention to new models of planet formation and migration in the outer solar system. We discuss the origins conundrum posed by the system's four small moons. We also elaborate on the implications of these scenarios…
We describe a fast, approximate method to characterize the orbits of satellites around a central binary in numerical simulations. A goal is to distinguish the free eccentricity -- random motion of a satellite relative to a dynamically cool orbit -- from oscillatory modes driven by the central binary's time-varying gravitational potential. We assess the performance of the method using the Kepler-16, Kepler-47, and Pluto-Charon systems. We then apply the method to a simulation of orbital damping in a circumbinary environment, resolving relative speeds between small bodies that are slow enough to…
Considering effects of tidal plus centrifugal stress acting on icy-rocks and the tensile strength thereof, icy-rocks being in the density range (1-2.4) g cm-3 which had come into existence as collisional ejecta (debris) in the vicinity of Pluto at the time when Pluto-Charon system came into being as a result of a giant impact of a Kuiper Belt Object on the primordial Pluto, it is shown, here, that these rocks going around Pluto in its vicinity are under slow disruption generating a stable ring structure consisting of icy-rocks of diameters in the range (20-90) km, together with fine dust and p…
Binary solar system objects are common and range from satellite systems with very large mass ratios $M_1/M_2$ to mass ratios very close to unity. A well-known example of a binary is the Pluto-Charon system. With Charon only eight times less massive than Pluto the question arises as for many other systems, why the mass-ratio is still close to unity. There is much evidence that (binary) planet(esimal) formation happened early, when the protoplanetary gas disk was still around. It is likely that (some of) these binaries grew up together subject to pebble accretion. Here we focus on the question o…
