This brief paper summarizes a “key general review” with the same title given at the IAU meeting in Rio de Janeiro. The intent of the review talk was to give a broad and well-illustrated overview of recent work on the icy middle and outer Solar system, in a style interesting for those astronomers whose gaze is otherwise drawn to more distant realms. The intent of this written review is the same.

The snow line in a gas disk is defined as the distance from the star beyond which the water ice is stable against evaporation. Since oxygen is the most abundant element after hydrogen and helium, the presence of ice grains can have important consequences for disk evolution. However, determining the position of the snow line is not simple. I discuss some of the important processes that affect the position of the snow line.

Icy grain mantles consist of small molecules containing hydrogen, carbon, oxygen and nitrogen atoms (e.g. H2O, CO, CO2, NH3). Such ices, present in different astrophysical environments (giant planets satellites, comets, dense clouds, and protoplanetary disks), are subjected to irradiation of different energetic particles: UV radiation, ion bombardment (solar and stellar wind as well as galactic cosmic rays), and secondary electrons due to cosmic ray ionization of H2. The interaction of these particles with astrophysical ice analogs has been the object of research over the last decades. However, there is a lack of information on the effects induced by the heavy ion component of cosmic rays in the electronic energy loss regime. The aim of the present work is to simulate of the astrophysical environment where ice mantles are exposed to the heavy ion cosmic ray irradiation.

Sample ice films at 13K were irradiated by nickel ions with energies in the 1-10 MeV/u range and analyzed by means of FTIR spectrometry. Nickel ions were used because their energy deposition is similar to that deposited by iron ions, which are particularly abundant cosmic rays amongst the heaviest ones.

In this work the effects caused by nickel ions on condensed gases are studied (destruction and production of molecules as well as associated cross sections, sputtering yields) and compared with respective values for light ions and UV photons.

The physical behaviour of methane and carbon dioxide clathrate hydrates, specific crystallographic ice crystals are of major importance for the earth and may control the stability of gases in many astrophysical bodies such as the planets, comets and possibly interstellar grains. Such models claim they provide an alternative trapping mechanism modifying the absolute and relative composition of icy bodies and can be at the source of late time injection of gaseous species in planetary atmospheres. However, there is a clear need to detect them directly. We provide in this study the laboratory recorded signatures of clathrate hydrates in the near to mid-infrared for astrophysical remote detection. These laboratory experiments will in a near future allow to follow the kinetic formation by diffusion in dedicated experiments, another important step to implement, to understand and model their possible presence in space.

The mean angular momentum associated with the collision of two celestial objects moving in almost circular heliocentric orbits was studied. The results of these studies were used to develop models of the formation of binaries at the stage of rarefied preplanetesimals. The models can explain a greater fraction of binaries formed at greater distances from the Sun. Sometimes there could be two centers of contraction inside the rotating preplanetesimal formed as the result of a collision between two rarefied preplanetesimals. Such formation of binaries could result in binaries with almost the same masses of components separated by a large distance. Formation of a disk around the primary could result because the angular momentum that was obtained by a rarefied preplanetesimal formed by collision was greater than the critical angular momentum for a solid body. One or several satellites of the primary could be formed from the disk.

Probabilities of collisions of migrating small bodies and dust particles produced by these bodies with planets were studied. Various Jupiter-family comets, Halley-type comets, long-period comets, trans-Neptunian objects, and asteroids were considered. The total probability of collisions of any considered body or particle with all planets did not exceed 0.2. The amount of water delivered from outside of Jupiter's orbit to the Earth during the formation of the giant planets could exceed the amount of water in Earth's oceans. The ratio of the mass of water delivered to a planet by Jupiter-family comets or Halley-type comets to the mass of the planet can be greater for Mars, Venus, and Mercury, than that for Earth.

We investigate the formation of terrestrial planets in the late stage of planetary formation using two-planet model. At that time, the protostar has formed for about 3 Myr and the gas disk has dissipated. In the model, the perturbations from Jupiter and Saturn are considered. We also consider variations of the mass of outer planet, and the initial eccentricities and inclinations of embryos and planetesimals. Our results show that, terrestrial planets are formed in 50 Myr, and the accretion rate is about 60% - 80%. In each simulation, 3 - 4 terrestrial planets are formed inside “Jupiter” with masses of 0.15 – 3.6 M⊕. In the 0.5 - 4AU, when the eccentricities of planetesimals are excited, planetesimals are able to accrete material from wide radial direction. The plenty of water material of the terrestrial planet in the Habitable Zone may be transferred from the farther places by this mechanism. Accretion may also happen a few times between two giant planets only if the outer planet has a moderate mass and the small terrestrial planet could survive at some resonances over time scale of 108 yr.

We simulate the chemical processes in the three evolution periods of the solar nebula, which are (i) the quasi-stationary prestellar cloud core, (ii) the gravitationally collapsing protostellar core, and (iii) the evolving gas-dust disk. Our purpose is to identify chemical parameters which reflect special aspects of the interactions between the gas and ice phase in the different periods, e.g. isotopic or molecular ratios. In this study we derive the D/H and 15N/14N ratio of selected compounds as well as the CO2/H2O ratio to measure the fraction of non-polar to polar ice in the grain mantles. The chosen ratios depend on the depletion-enrichment relation between the ice and gas phases driven by the thermal evolution in each period, especially during the collapse. Hence, we have made great efforts in order to derive realistic and compact hydrodynamic models to describe the evolutionary periods of the solar nebula.

The Oort cloud, which corresponds to the furthest boundary of our Solar System, is considered as the main reservoir of long period comets. This cloud is likely a residual of the Solar System formation due to the gravitational effects of the young planets on the remaining planetesimals. Given that the cloud extends to large distances from the Sun (several times 10 000 AU), the bodies in this region have their trajectories affected by the Galactic environment of the Solar System. This environment is responsible for the re-injection of the Oort cloud comets into the planetary region of the Solar System. Such comets, also called “new comets”, are the best candidates to become Halley type or “old” long period comets under the influence of the planetary gravitational attractions. Consequently, the flux of new comets represents the first stage of the long trip from the Oort cloud to the observable populations of comets. This is why so many studies are still devoted to this flux.

The different perturbers related to the Galactic environment of the Solar System, which have to be taken into account to explain the flux are reviewed. Special attention will be paid to the gravitational effects of stars passing close to the Sun and to the Galactic tides resulting from the difference of the gravitational attraction of the Galaxy on the Sun and on a comet. The synergy which takes place between these two perturbers is also described.

We review two main scenarios that may have implanted Sedna, 2004 VN112 and 2000 CR105 on their current peculiar orbits. These scenarios are based on perihelion lifting mechanisms that acted upon primordial scattered icy bodies. Supposing that the Sun was formed in a dense star cluster and that the gas giants were also forming while the cluster was still dense, an inner Oort cloud that includes Sedna at its inner edge could have been formed by the circularization of icy leftovers orbits scattered by the gas giants. A putative planetary mass solar companion can also produce a similar population of icy bodies through a perihelion lifting mechanism induced by secular resonances from the companion. A third scenario also dependent on a primordial dense cluster may contribute to adding a significant number of extrasolar icy bodies to the main solar component of the population created by the cluster model. These extrasolar objects are transferred to Sun orbits from the scattered disk of passing stars that were numerous in the dense primordial environment. We compare the scenarios as to the orbital distribution of the induced populations as well as their total mass. We conclude that both the cluster model and the solar companion model can produce icy body populations consistent with Sedna's orbit. It is also quite possible that this inner Oort cloud may be composed of roughly one tenth of extrasolar objects.

We analyze a sample of 58 Oort cloud comets (OCCs) (original orbital energies x in the range 0 < x < 100, in units of 10−6 AU−1), plus 45 long-period comets with negative orbital energies or poorly determined or undetermined x, discovered during the period 1999-2007. To analyze the degree of completeness of the sample, we use Everhart's (1967 Astr. J 72, 716) concept of “excess magnitude” (in magnitudes × days), defined as the integrated magnitude excess that a given comet presents over the time above a threshold magnitude for detection. This quantity is a measure of the likelihood that the comet will be finally detected. We define two sub-samples of OCCs: 1) new comets (orbital energies 0 < x < 30) as those whose perihelia can shift from outside to the inner planetary region in a single revolution; and 2) inner cloud comets (orbital energies 30 ≤ x < 100), that come from the inner region of the Oort cloud, and for which external perturbers (essentially galactic tidal forces and passing stars) are not strong enough to allow them to overshoot the Jupiter-Saturn barrier. From the observed comet flux and making allowance for missed discoveries, we find a flux of OCCs brighter than absolute total magnitude 9 of ≃0.65 ± 0.18 per year within Earth's orbit. From this flux, about two-thirds corresponds to new comets and the rest to inner cloud comets. We find striking differences in the q-distribution of these two samples: while new comets appear to follow an uniform q-distribution, inner cloud comets show an increase in the rate of perihelion passages with q.

Preliminary results of an investigation on the problem of hyperbolic comets are presented and discussed.

By means of a simple non-gravitational force model of the cometary nucleus, which relies on the observed light curves assumed to be a good representation of the water sublimation rate, we estimate the masses of a sample of long-period comets (LPCs).

A critical issue of our method is the assumption of a correlation between visual heliocentric magnitudes and water production rates. This is a necessary assumption because of the sparse observational data of gas production rates (with the exception of very few comets like Hale-Bopp or Hyakutake). In this regard we present here a new correlation for LPCs. We also present the preliminary results for the masses of comets Hale-Bopp and Hyakutake.

We present a study of the dynamical evolution of plutinos recently escaped from the resonance through numerical simulations. It was shown in previous works the existence of weakly chaotic orbits in the plutino population that diffuse very slowly finally diving into a strong chaotic region. These orbits correspond to long-term plutino escapers and then represent the plutinos that are escaping from the resonance at present. Then, we divided the numerical simulation in two parts. First, we develop a numerical simulation of 20,000 test particles in the resonance in order to detect the long-term escapers. We set the initial orbital elements such that cover the present observational range of orbital elements of plutinos. Second, we perform a numerical simulation of the selected escaped plutinos in order to study their dynamical post escaped behavior. We describe and characterize the routes of escape of plutinos and their evolution in the Centaur zone. Also, we obtain that Centaurs coming from plutinos would represent a fraction of less than 6% of the total Centaur population.

Perturbations from asteroids and Trans-Neptunian Objects affect significantly on the orbits of planets and should be taken into account when high-accuracy planetary ephemerides are constructed. On the other hand, from an analysis of motion of the major planets by processing of precise measurements of spacecraft a limitation on the total TNO mass may be obtained. To estimate influence of TNO on motion of planets the largest 21 TNO have been included into the process of simultaneous numerical integration, and positions of planets obtained with taking for TNO have been compared with positions of planets of numerical EPM ephemeris of IAA RAS constructed without these objects. The perturbations of other TNO have been modeled by the perturbation from a circular ring having a radius 43 AU and different masses. It has been shown that all the test masses of the TNO ring except the minimum mass (5.26⋅10−8M⊙) are too large and make the data residuals worse. Thus, the upper limit of the total mass of all TNO including Pluto, the 21 largest TNO and the TNO ring (with the 43 AU radius) should not exceed 8.04⋅10−8M⊙.

In this work, we study the impactor flux on Pluto and Charon due to the collisional evolution of Plutinos.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. Our results suggest that if 1 Pluto-sized object is in this resonance, the flux of D = 2 km Plutinos on Pluto is ~4–24 percent of the flux of D = 2 km Kuiper Belt projectiles on Pluto. However, with 5 Pluto-sized objects in the resonance, the contribution of the Plutino population to the impactor flux on Pluto may be comparable to that of the Kuiper Belt. As for Charon, if 1 Pluto-sized object is in the 3:2 resonance, the flux of D = 2 km Plutinos is ~10–63 percent of the flux of D = 2 km impactors coming from the Kuiper Belt. However, with 5 Pluto-sized objects, the Plutino population may be a primary source of the impactor flux on Charon. We conclude that it is necessary to specify the Plutino size distribution and the number of Pluto-sized objects in the 3:2 Neptune resonance in order to determine if the Plutino population is a primary source of impactors on the Pluto-Charon system.

We present results from numerical simulations of a Jupiter family comet (JFC) population (orbital periods P < 20 yr and Tisserand parameters in the range 2 < T < 3.1) originated in the Scattered Disk and transferred to the Jupiter's zone through gravitational interactions with the Jovian planets. We shall call ‘non-JFCs’ those comets coming from the same source, but that do not fulfill the previous criteria (mainly because they have periods P > 20 yr). We have carried out series of numerical simulations of fictitious comets with a purely dynamical model and also with a more complete dynamical - physical model that includes besides nongravitational forces, sublimation and splitting mechanisms. We obtained better fits with models including physical effects, and in particular our best fits are for four splitting models with a relative weak dependence on q, and a mass loss in every splitting event that is smaller/greater for higher/lower frequencies respectively. The mean lifetime of JFCs with radii R > 1 km and q < 1.5 AU is found to be of about 150-200 revolutions (~103 yr). We find a total population of JFCs with radii R > 1 km within Jupiter's zone of 450 ± 50 and a mean lifetime of about 150-200 revolutions (~103 yr) for those getting q < 1.5 AU. The population of JFCs + non-JFCs with radii R > 1 km in Jupiter-crossing orbits may be about ~2,250 ± 250. Most of non-JFCs have perihelia close to Jupiter's orbit.

We also present maps of the densest zones of JFCs in the orbital element space.

Comet-like orbits with low perihelion distances tend to be affected by relativistic effects. In this work we discuss the origin of the relativistic corrections, how they affect the orbital evolution and how to implement these corrections in a numerical integrator. We also propose a model that mimics the principal relativistic effects and, contrary to the original “exact” formula, has low computational cost. Our model is appropriated for numerical simulations but not for precise ephemeris computations.

The state of knowledge about the structure and composition of icy satellite interiors has been significantly extended by combining direct measurements from spacecraft, laboratory experiments, and theoretical modeling. Interior models of icy bodies will certainly benefit from future missions to the outer solar system, providing new and improved constraints on the surface chemistry, bulk composition and degree of internal differentiation, possible heterogeneities in radial mass distribution, the presence and extent of liquid reservoirs, and the amount of tidal heating for each target body. Here we summarize geophysical constraints on the interior structure and composition of selected Jovian and Saturnian icy satellites and investigate conditions under which potentially habitable liquid water reservoirs could be maintained. Future geophysical exploration which includes gravitational and magnetic field sounding from low-altitude orbit and close flyby, combined with altimetry data and in-situ monitoring of tidally-induced surface distortion and time-variable magnetic fields, would impose important constraints on the interiors of outer planet satellites.

Detailed evolutionary calculations spanning 4.6 × 109 yr are presented for (a) a model representing main-belt comet 133P/Elst-Pizarro, considering different initial mixtures of ices and dust, and (b) a Kuiper Belt object heated by radioactive decay, growing in size from an initial radius of 10 km to a final 250 km.

It is shown that for the main-belt comet only crystalline H2O ice may survive in the interior of the nucleus, and may be found at depths ranging from ~50 to 150 m. Other volatiles will be completely lost. For the large Kuiper Belt object, evaporation and flow of water and vapor gradually remove the water from the core and the final (present) structure is differentiated, with a rocky, highly porous core of 80 km radius. Outside the core, due to refreezing of water vapor, a compact, ice-rich layer forms, a few tens of km thick. The amorphous ice is preserved in an outer layer about 20 km thick.