Impacts of thrusting,extensional faulting,and glaciation on cratering records of Pluto’s largest moon Charon:Implications for the evolution of Kuiper belt objects

A first-order question in the studies of the Solar System is how its outer zone known as the Kuiper belt was created and evolved.Two end-member models, involving coagulation vs. streaming instability, make different predictions-testable by the cratering history of Kuiper Belt Objects(KBOs)-about the cumulative size-frequency distribution(SFD) of the KBOs. Among all of the imaged KBOs, Pluto’s largest icy moon, Charon, appears to preserve the largest size range of seemingly undisturbed craters, their diameters(D) on Charon ranging from < 1 km to > 220 km. Current work shows that Charon’s craters with D < 10-20 km are fewer than those expected by the coagulation mechanism, but whether this is an artifact of post-cratering modification of smaller craters is unknown. We address this issue by conducting systematic photogeological mapping and performing detailed landform analysis using the highest resolution images obtained by the New Horizons spacecraft, which reveal a range of differentiable terrains on Charon. The most important findings of our work include(1) truncation and obliteration 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 of the northern encountered hemisphere,(2) lobate ridges, lobate knob trains, and lobate aprons resembling glacial moraine landforms on Earth,(3) dendritic channel systems containing hanging valleys,and(4) locally striated surfaces defined by parallel ridges, knob trains, and grooves that are > 40-50 km in length. The above observations and the topographic dichotomy of Charon’s encountered hemisphere can be explained by a landscape-evolution model that involves(i)a giant impact that created the Vulcan Planitia basin and the extensional fault zone along its northern rim,(ii) a transient atmosphere capable of driving N2-ice glacial erosion of the water-ice bedrock and transporting water-ice debris to sedimentary basins,(iii) regional glacial erosion and transport of earlier emplaced impact ejecta deposits from the highlands of Oz Terra into the lowland basin of Vulcan Planitia,(iv) syn-glaciation north-trending thrusting, interpreted to have been induced by Charon’s despinning, and(v) the development of a water-ice debris cover layer over subsurface N2 ice below Vulcan Planitia during global deglaciation. The infilling of the Vulcan Planitia could have been accompanied by cryovolcanism. The extensive modification of impact craters means that the size-frequency distributions of Charon’s craters should serve only as a lower bound when used to test formation mechanisms proposed for Kuiper belt objects.

Formation of the Kuiper Belt by Long Time-Scale Migration of Jovian Planets

The orbital migration of Jovian planets is believed to have played an important role in shaping the Kuiper Belt. We investigate the effects of the long time-scale （2 ×107 yr） migration of Jovian planets on the orbital evolution of massless test particles that are initially located beyond 28 AU. Because of the slowness of the migration, Neptune＇s mean motion resonances capture test particles very efficiently. Taking into account the stochastic behavior during the planetary migration and for proper parameter values, the resulting concentration of objects in the 3：2 resonance is prominent, while very few objects enter the 2：1 resonance, thus matching the observed Kuiper Belt objects very well. We also find that such a long time-scale migration is favorable for exciting the inclinations of the test particles, because it makes the secular resonance possible to operate during the migration. Our analyses show that the us secular resonance excites the eccentricities of some test particles, so decreasing their perihelion distances, leading to close encounters with Neptune, which can then pump the inclinations up to 20°.

Formation and Evolution of Pluto and Kuiper Belt

Despite Pluto’s demotion to dwarf planet status,people are still attached to it.Scientists combined observations of Pluto from NASA’s New Horizons probe with observations of comet Churyumov-Gerasimenko from the European Space Agency’s Rosetta probe and found that Pluto’s nitrogen abundance matched the pattern of about a billion comets,which led to the theory that Pluto is made of about a billion comets.Yet they don’t know exactly when or where these comets originated.By studying the origin and orbit of comets,the author of this paper found that the material that condensed Pluto was mainly comets and dust ejected by Neptune,and the Kuiper Belt objects were condensed by material ejected by Neptune toward the outer side of its orbit.

Trailing (L5) Neptune Trojans: 2004 KV18 and 2008 LC18

The population of Neptune Trojans is believed to be bigger than that of Jupiter Trojans and that of asteroids in the main belt, although only eight members of this distant asteroid swarm have been observed up to now. Six leading Neptune Trojans around the Lagrange point L4 discovered earlier have been studied in detail, but two trailing ones found recently around the L5 point, 2004 KV18 and 2008 LC18, have not yet been investigated. We report our investigations on the dynamical behaviors of these two new Neptune Trojans. Our calculations show that the asteroid 2004 KV18 is a temporary Neptune Trojan. Most probably, it was captured into the trailing Trojan cloud no earlier than 2.03 ×105 yr ago, and it will not maintain this position later than 1.65 × 105 yr in the future. Based on the statistics from our orbital simulations, we ar- gue that this object is more like a scattered Kuiper belt object. By contrast, the orbit of 2008 LC18 is much more stable. Among the clone orbits spreading within the orbital uncertainties, a considerable portion of clones may survive on the L5 tadpole orbits for 4 Gyr. The strong dependence of the stability on the semimajor axis and resonant angle suggests that further observations are badly required to constrain the orbit in the stable region. We also discuss the implications of the existence and dynamics of these two trailing Trojans over the history of the solar system.

Studying the Equilibrium Points of the Modified Circular Restricted Three-body Problem: The Case of Sun–Haumea System

We intend to study a modified version of the planar Circular Restricted Three-Body Problem(CRTBP) by incorporating several perturbing parameters. We consider the bigger primary as an oblate spheroid and emitting radiation while the small primary has an elongated body. We also consider the perturbation from a disk-like structure encompassing this three-body system. First, we develop a mathematical model of this modified CRTBP.We have found there exist five equilibrium points in this modified CRTBP model, where three of them are collinear and the other two are non-collinear. Second, we apply our modified CRTBP model to the Sun–Haumea system by considering several values of each perturbing parameter. Through our numerical investigation, we have discovered that the incorporation of perturbing parameters has resulted in a shift in the equilibrium point positions of the Sun–Haumea system compared to their positions in the classical CRTBP. The stability of equilibrium points is investigated. We have shown that the collinear equilibrium points are unstable and the stability of non-collinear equilibrium points depends on the mass parameter μ of the system. Unlike the classical case, non-collinear equilibrium points have both a maximum and minimum limit of μ for achieving stability. We remark that the stability range of μ in non-collinear equilibrium points depends on the perturbing parameters. In the context of the Sun–Haumea system, we have found that the non-collinear equilibrium points are stable.

Comprehensive Research on the Origin of the Solar System Structure by Quantum-like Model

A quantum-like model of gravitational system is introduced to explore the formation of the solar system structure. In this model, the chaos behavior of a large number of original nebular particles in a gravitational field can be described in terms of the wave function satisfying formal Schr?dinger equation, in which the Planck constant is replaced by a constant on cosmic scale. Numerical calculation shows that the radial distribution density of the particles has the character of wave curves with decreasing amplitudes and elongating wavelengths. By means of this model, many questions of the solar system, such as the planetary distance, mass, energy, angular momentum, the distribution of satellites, the structure of the planetary rings, and the asteroid belt and the Kuiper belt etc., can be explained in reason. In addition, the abnormal rotations of Venus and Mercury can be naturally explained by means of the quantum-like model.