Near-parabolic cometary flux in the outer solar system

The flux of near-parabolic comets in the outer-planetary region is estimated on the presumption that the major planets and the galactic tide control the dynamics of comets. It is found that the flux of the Oort cloud comets (semi-major axis > 20000 AU) is similar to the case of a strong comet shower derived on the presumption that the galactic tidal force were not operative. On the other hand, the flux of comets with semi-major axes <- 20000 AU is found to be an increasing function of q (perihelion distance) until q reaches 20 AU, while for a 45000 AU it is a rapidly increasing function for q 12 AU. In other words, for comets of the inner extension of the Oort cloud the planetary perturbation acts as a strong barrier for them to penetrate into the inner planetary region.     

Production of organic molecules in the outer solar system by proton irradiation: Laboratory simulations

In the past few years considerable attention has been given to the determination of likely compounds that could account for the various colors observed in the outer solar system: and to possible formation mechanisms for these compounds. Many experiments have been done using electrical discharges (Chadha, M. S., et al., 1971, Icarus15, 39) and ultraviolet light (Khare, B. N., and Sagan, C., 1973, Icarus20, 311) on mixtures of CH₄, NH₃, and H₂S, which are most likely the dominant minor constituents of the atmospheres of Jupiter, Saturn, Titan, and possibly the other satellites early in their histories. Colored polymers, usually brownish-red, have been produced in these experiments. With the passage of Pioneer 10 around Jupiter, there is another source of energy worthy of consideration, energetic protons (and electrons). Preliminary experiments to investigate the formation of colored polymers and other interesting molecules by the irradiation of gas mixtures by protons are discussed. Two to four Mev protons were used, with corresponding beam fluxes (as measured at 6R_J from the planet) equivalent to approximately 80 Earth years at Jupiter per hour of exposure. As in the other types of experiments, colored polymers have been produced. An important feature of this work is the presence or absence of absorption at 5 μm in the different materials produced; Titan is quite dark at this wavelength and Io is fairly bright. Such features may provide criteria for accepting or rejecting various materials produced in these experiments as reasonable coloring agents for the outer solar system.     

Investigation of the long-periodic orbits of Trojan-type asteroids in the outer solar system

The present paper demonstrates the results of the numerical integration of equations of motion of a infinitesimal mass pleased in the neighborhood of the triangular point of the Sun-planet system. There are presented the results for the outer solar system, i.e. for Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. The long-periodic solutions were searched for the distance from the Lagrangian point changing from ±0.01 to ±0.10 in canonical units. The Trojans of those planets have the circle, tadpole, horseshoe and irregular shape of their orbits. Same of those test particles showed a close approach to planet. Other of those collided with planet and then was removed from the solar system. The tadpole, circle and same trajectories surveyed integration for 100,000 years. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ethane ices in the outer Solar System: Spectroscopy and chemistry

We report recent experiments on ethane ices made at temperatures applicable to the outer Solar System. New near- and mid-infrared data for crystalline and amorphous ethane, including new spectra for a seldom-studied solid phase that exists at 35-55 K, are presented along with radiation-chemical experiments showing the formation of more-complex hydrocarbons.     

The Kozai resonance in the outer solar system and the dynamics of long-period comets

We consider the secular evolution of the orbits of bodies in the Outer Solar System under the perturbations of the jovian planets assumed on coplanar and circular orbits. Through the approach used for asteroidal belt by Yoshihide Kozai in 1962, we obtain that the Kozai resonance do not affect the behavior of bodies belonging to the Kuiper belt but concerns the long-timescale evolution of long-period comets. In particular this resonance appears as a process contributing to produce Sun-grazer comets.     

Preliminary limits on deviation from the inverse-square law of gravity in the solar system:a power-law parameterization

New physics beyond the standard model of particles might cause a deviation from the inverse-square law of gravity. In some theories,it is parameterized by a power-law correction to the Newtonian gravitational force,which might originate from the simultaneous exchange of particles or modified and extended theories of gravity. Using the supplementary advances of the perihelia provided by INPOP10a(IMCCE,France) and EPM2011(IAA RAS,Russia) ephemerides,we obtain preliminary limits on this correction. In our estimation,we take the Lense-Thirring effect due to the Sun's angular momentum into account. The parameters of the power-law correction and the uncertainty of the Sun's quadrupole moment are simultaneously estimated with the method of minimizing χ2. From INPOP10 a,we find N = 0.605 for the exponent of the power-law correction. However,from EPM2011,we find that,although it yields N = 3.001,the estimated uncertainty in the Sun's quadrupole moment is much larger than the value given by current observations. This might be caused by the intrinsic nonlinearity in the power-law correction,which makes the estimation very sensitive to the supplementary advances of the perihelia.     

New upper limits on deviation from the inverse-square law of gravity in the solar system:a Yukawa parameterization

New physics beyond the standard model of particles might cause deviation from the inverse-square law of gravity.In many theoretical models of modified gravity,it is parameterized by the Yukawa correction to the Newtonian gravitational force in terms of two parameters α and λ.Here α is a dimensionless strength parameter and λ is a length scale.Using the supplementary advances in perihelia provided by INPOP10a and EPM2011 ephemerides,we obtain new upper limits on the deviation from the inverse-square law when the uncertainty of the Sun's quadrupole moment is taken into account.We find that INPOP10a yields the upper limits as α = 3.1 × 10-11and λ = 0.15 au,and EPM2011 gives α = 5.2 × 10-11and λ = 0.21 au.In both of them,α is at least 10 times less than the previous results.     

A review of possible optical absorption features of oxygen molecules in the icy surfaces of outer solar system bodies

In this review we provide the data needed to interpret remote spectroscopic studies of O₂ molecules embedded in the icy surfaces of outer solar system bodies. O₂ produced by radiolysis has been seen in the gas phase and as the so-called ‘solid O₂’ trapped in the icy surfaces of Ganymede, Europa and Callisto. It may also have been indirectly observed on a number of objects by its radiolysis product, O₃. These observations indicate the importance of O₂ for understanding the chemical processes occurring on icy outer solar system surfaces. Therefore, the published absorption spectra of gaseous, liquid and solid O₂ and of O₂ embedded in H₂O ice are reviewed in some detail. Particular emphasis has been placed on the presentation of transition probabilities for the various O₂ spectral series so that their relative importances can be assessed when they are used for modelling the radiation chemistry occurring in such environments.     

Chaos in Hill's generalized problem: from the solar system to black holes

We generalize the well‐known Hill's circular restricted three‐body problem by assuming that the primary generates a Schwarzschild‐type field of the form U = A/r + B/r³. The term in B influences the particle, but not the far secondary. Many concrete astronomical situations can be modelled via this problem. For the two‐body problem primary‐particle, a homoclinic orbit is proved to exist for a continuous range of parameters (the constants of energy and angular momentum, and the field parameter B > 0). Within the restricted three‐body system, we prove that, under sufficiently small perturbations from the secondary, the homoclinic orbit persists, but its stable and unstable manifolds intersect transversely. Using a result of symbolic dynamics, this means the existence of a Smale horseshoe, hence chaotic behaviour. Moreover, we find that Hill's generalized problem (in our sense) is nonintegrable. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The opposition effect in the outer Solar system: A comparative study of the phase function morphology

In this paper, we characterize the morphology of the disk-integrated phase functions of satellites and rings around the giant planets of our solar system. We find that the shape of the phase function is accurately represented by a logarithmic model [Bobrov, M.S., 1970. Physical properties of Saturn's rings. In: Dollfus, A. (Ed.), Surfaces and Interiors of Planets and Satellites. Academic, New York, pp. 376-461]. For practical purposes, we also parametrize the phase curves by a linear-exponential model [Kaasalainen, S., Muinonen, K., Piironen, J., 2001. Comparative study on opposition effect of icy solar system objects. Journal of Quantitative Spectroscopy and Radiative Transfer 70, 529-543] and a simple linear-by-parts model [Lumme, K., Irvine, W.M., 1976. Photometry of Saturn's rings. Astronomical Journal 81, 865-893], which provides three morphological parameters: the amplitude A and the half-width at half-maximum (HWHM) of the opposition surge, and the slope S of the linear part of the phase function at larger phase angles.Our analysis demonstrates that all of these morphological parameters are correlated with the single-scattering albedos of the surfaces.By taking more accurately into consideration the finite angular size of the Sun, we find that the Galilean, Saturnian, Uranian and Neptunian satellites have similar HWHMs (?0.5^°), whereas they have a wide range of amplitudes A. The Moon has the largest HWHM (∼2^°). We interpret that as a consequence of the “solar size bias”, via the finite angular size of the Sun which varies dramatically from the Earth to Neptune. By applying a new method that attempts to morphologically deconvolve the phase function to the solar angular size, we find that icy and young surfaces, with active resurfacing, have the smallest values of A and HWHM, whereas dark objects (and perhaps older surfaces) such as the Moon, Nereid and Saturn's C ring have the largest A and HWHM.Comparison between multiple objects also shows that solar system objects belonging to the same planet have comparable opposition surges. This can be interpreted as a “planetary environmental effect” that acts to locally modify the regolith and the surface properties of objects which are in the same environment.