In the final phase of terrestrial planet formation, planetary embryos and planetesimals are the building blocks for the growth of rocky planets. In this investigation, we study the dynamical behaviour of a circumstellar disk in an inclined binary star system. The disk consists of 2000 planetesimals and 25 embryos and is distributed between 1 and 4 au around the primary star. To compute the gravitational interaction of the whole system, we use our recently developed GPU N-body code GANBISS. GANBISS treats all collision as perfect merging and delivers the impact parameters that will be used to distinguish between different collision outcomes.

Planets open deep gaps in protoplanetary discs when their mass exceeds a gap opening mass, Mgap. We use one- and two-dimensional simulations to study planet gap opening in discs with angular momentum transport powered by MHD disc winds. We parameterise the efficiency of the MHD disc wind angular momentum transport through a dimensionless parameter αdw, which is an analogue to the turbulent viscosity αv. We find that magnetised winds are much less efficient in counteracting planet tidal torques than turbulence is. For discs with astrophysically realistic values of αdw, Mgap is always determined by the residual disc turbulence, and is a factor of a few to ten smaller than usually obtained for viscous discs. We introduce a gap opening criterion applicable for any values of αv and αdw that may be useful for planet formation population synthesis.

We present the results of a search for additional exoplanets in all multiplanetary systems discovered to date, employing a logarithmic spacing between planets in our Solar System known as the Titius–Bode (TB) relation. We use the Markov Chain Monte Carlo method and separately analyse 229 multiplanetary systems that house at least three or more confirmed planets. We find that the planets in $\sim 53\%$ of these systems adhere to a logarithmic spacing relation remarkably better than the Solar System planets. Using the TB relation, we predict the presence of 426 additional exoplanets in 229 multiplanetary systems, of which 197 candidates are discovered by interpolation and 229 by extrapolation. Altogether, 47 predicted planets are located within the habitable zone of their host stars, and 5 of the 47 planets have a maximum mass limit of 0.1–2 ${\rm M}_{\oplus}$ and a maximum radius lower than 1.25 ${\rm R}_{\oplus}$ . Our results and prediction of additional planets agree with previous studies’ predictions; however, we improve the uncertainties in the orbital period measurement for the predicted planets significantly.

Understanding the physical structure of the planet formation environment, the protoplanetary disk, is essential for the interpretation of high resolution observations of the dust and future observations of the magnetic field structure. Observations of multiple transitions of molecular species offers a unique view of the underlying physical structure through excitation analyses. Here we describe a new method to extract high-resolution spectra from low-resolution observations, then provide two case studies of how molecular excitation analyses were used to constrain the physical structure in TW Hya, the closest protoplanetary disk to Earth.

The pore structure of vapour deposited ASW is poorly understood, despite its importance to fundamental processes such as grain chemistry, cooling of star forming regions, and planet formation. We studied structural changes of vapour deposited D2O on intra-molecular to 30 nm length scales at temperatures ranging from 18 to 180 K and observed enhanced mobility from 100 to 150 K. An Arrhenius type model describes the loss of surface area and porosity with a common set of kinetic parameters. The low activation energy (428 K) is commensurate with van der Waals forces between nm-scale substructures in the ice. Our findings imply that water porosity will always change with time, even at low temperatures.

As observational facilities improve, providing new insights into the chemistry occurring in protoplanetary disks, it is important to develop more complete pictures of the processes that shapes the chemical evolution of materials during this stage of planet formation. Here we describe how primitive meteorites in our own Solar System can provide insights into the processes that shaped planetary materials early in their evolution around the Sun. In particular, we show how this leads us to expect protoplanetary disks to be very dynamic objects and what modeling and laboratory studies are needed to provide a more complete picture for the early chemical evolution that occurs for planetary systems.

In the standard formation scenario of planetary systems, planets form from a protoplanetary disk that consists of gas and dust. The scenario can be divided into three stages: (1) formation of planetesimals from dust, (2) formation of protoplanets from planetesimals, and (3) formation of planets from protoplanets. In stage (1), planetesimals form from dust through coagulation of dust grains and/or some instability of a dust layer. Planetesimals grow by mutual collisions to protoplanets or planetary embryos through runaway and oligarchic growth in stage (2). The final stage (3) of terrestrial planet formation is giant impacts among protoplanets while sweeping residual planetesimals. In the present paper, we review the elementary processes of terrestrial planet formation and discuss the extension of the standard scenario.

The present-day Earth with its innumerable life forms is a product of cosmic evolution starting with the formation of our galaxy and the dense gas clouds within it, and proceeding through the contraction of one of those clouds about 4.6 Gyr ago, first into filaments and then one or more protostellar disks, planets, and central stars, one of which was our Sun. Radioactive debris from a massive nearby star was included. The planets themselves formed through coagulation, accretion, and fragmentation of solid bodies. Habitability depends on a delicate balance between disk accretion by gravity and dispersal by the central star, which determine the size of the planet and its gaseous envelope, combined with a long period of stellar radiation, which has to disperse this envelope but leave a hospitable secondary atmosphere. The final step toward life involves even more complexity as self-replicating bio-molecules form with ever increasing stability.

The origin of the planets atmosphere is a profound question of comparative planetology. There are two competing models, i.e. outgassing from the interior or late delivery from comets or volatiles-rich asteroids after most of the planet has been formed, of which the former is currently preferred. Meteorite compositions as well as radial mixing during accretion derived from accretion models suggest that the building blocks of the terrestrial planets contained some volatiles. Processes like dehydration by hydrous melting, oxidation, impact devolatilization, and in particular degassing during magma ocean solidification will then lead to a significant volatile loss of the interior and to the formation of a dense atmosphere during the early stages of planetary evolution. These processes are also responsible for the oxidation state of this early atmosphere, i.e. whether it was more reduced or oxidized. Although this early volatile loss was very efficient, the interior probably retained some water. This was distributed in the subsequent evolution between interior and atmosphere, as well as on the surface as liquid water in case of favorable temperature and pressure conditions. The main processes responsible for the water distribution are volcanic outgassing driven by partial melting of the silicate mantle and formation of the crust and recycling of water-rich crustal material. Here, an important difference between the terrestrial planets is the tectonic style prevailing on the planet. For the Earth with its plate tectonics, recycling of water is very efficient and can even balance the outgassing. For terrestrial planets in the stagnant lid regime of mantle convection such as Mars, the exchange of water between the interior and the surface/atmosphere is mainly in one direction and results in a continuous depletion of the interior. In this talk, I will briefly review our current knowledge on these interactions between interior and atmosphere and on the problem we are facing to better understand the influence of the interior on the habitability of a planet.

Final water inventories of newly formed terrestrial planets are shaped by their collision history. A setting where volatiles are transported from beyond the snowline to habitable-zone planets suggests collisions of very dry with water-rich bodies. By means of smooth particle hydrodynamics (SPH) simulations we study water delivery in scenarios where a dry target is hit by a water-rich projectile, focusing on hit-and-run encounters with two large surviving bodies, which probably comprise about half of all similar-sized collisions (Genda et al. 2017).

New data obtained by space missions to various objects in the Solar system and observations of the outer Solar system and exoplanets by space and ground-based telescopes allowed us to conclude that the atmospheric escape plays an important role in the evolution of the terrestrial planets in the Solar system. We present the recent results of application of the kinetic approach to the problem of neutral escape from planetary atmospheres. As an example, the recent measurements by Mars Express and MAVEN spacecraft are compared with the calculations of neutral escape with the aim to understand the atmospheric loss at Mars. Also the recent calculations of the mass-loss rates of the hot Neptune and Jupiter atmospheres are presented.

We discuss the factors influencing the formation and gravitational fragmentation of protostellar discs. We start with a review of how observations of prestellar cores can be analysed statistically to yield plausible initial conditions for simulations of their subsequent collapse. Simulations based on these initial conditions show that, despite the low levels of turbulence in prestellar cores, they deliver primary protostars and associated discs which are routinely subject to stochastic impulsive perturbations; consequently misalignment of the spins and orbits of protostars are common. Also, the simulations produce protostars that collectively have a mass function and binary statistics matching those observed in nearby star-formation regions, but only if a significant fraction of the turbulent energy in the core is solenoidal, and accretion onto the primary protostar is episodic with a duty cycle $\stackrel{>}{\sim }3\,000\,{\rm yr}$. Under this circumstance, a core typically spawns between 4 and 5 protostars, with high efficiency, and the lower mass protostars are mainly formed by disc fragmentation. The requirement that a proto-fragment in a disc lose thermal energy on a dynamical timescale dictates that there is a sweet spot for disc fragmentation at radii $70\,{\rm AU}\stackrel{<}{\sim }R\stackrel{<}{\sim }100\,{\rm AU}$ and temperatures $10\,{\rm K}\stackrel{<}{\sim }T\stackrel{<}{\sim }20\,{\rm K}$, and this might explain the brown dwarf desert.

We present preliminary results of models of terrestrial planet formation using on the one hand classical numerical integration of hundreds of small bodies on CPUs and on the other hand—for comparison—the results of our GPU code with thousands of small bodies which then merge to larger ones. To be able to determine the outcome of collision events we use our smooth particle hydrodynamics (SPH) code which tracks how water is lost during such events.

Main sequence stars hosting extreme quantities of inner planetary system debris are likely experiencing transient dust production events. The nature of these events, if they can be unambiguously attributed to a single process, can potentially inform us on the formation and/or early evolution of rocky Earth-like planets. In this contribution I examine some of the dustiest main sequence stars known and three processes that may be capable of reproducing their observed properties. Through this activity I also make an estimate for the likelihood of an A-type star to have an asteroid belt-like planetesimal population.

We look at applications of recent work in theoretical and experimental spectroscopy for the analysis of IR data concerning giant planets, Titan and possibly exoplanets.

The unprecedented sensitivity and imaging capabilities offered by the Atacama Large Millimeter Array (ALMA) are transforming our understanding of protoplanetary disks and, hence, of planet formation. In this brief chapter, I first discuss the main results and caveats related to the measurement of the mass of solids in protoplanetary disks based on millimeter-wave observations. I then present a recent analysis of the ALMA observations of the HL Tau disk, which suggests that the observed circular rings might be due to the tidal interaction between Saturn mass planets and the circumstellar material. In the conclusion, I argue that the existing observations of protoplanetary disks suggest that planets might form very early on, perhaps at the same time as the formation of the disk itself.

We look at the icy moons in our outer solar system in which we find organics and the possibility for habitabile conditions therein.

We use radar images with decameter resolution to measure the sizes, shapes, spin states, mutual orbits, masses, and densities of components of asteroid binaries and triples. We simulate the spin-orbit dynamics of these systems and map the possible spin configurations of the satellites on surface of section plots. The presence of chaotic regions in the phase space has important consequences for the evolution of binary asteroids. It may substantially increase spin synchronization timescales, delay BYORP-type evolution, and extend the lifetime of binaries.

We develop numerical tools to detect and quantify the mass and area for all structures of a protoplanetary disk with different optical depths. We consider two planets of 0.1 MJ. They are initially at 12.5 and 20 AU embedded in a viscous disk, where planetary mass accretion and migration are allowed. We find a gap region with optically thick streams, this region is characterized by an optically thin filling factor near to 1. Additionally, we generate the Spectral Energy Distribution of each structure of the disk considering silicate dust. Our tools are useful to identify the locations of structures and sub-structures as possible sites where the material is accumulated.

We investigate the outcome of collisions of Ceres-sized planetesimals composed of a rocky core and a shell of water ice. These collisions are not only relevant for explaining the formation of planetary embryos in early planetary systems, but also provide insight into the formation of asteroid families and possible water transport via colliding small bodies. Earlier studies show characteristic collision velocities exceeding the bodies' mutual escape velocity which—along with the distribution of the impact angles—cover the collision outcome regimes ‘partial accretion’, ‘erosion’, and ‘hit-and-run’ leading to different expected fragmentation scenarios. Existing collision simulations use bodies composed of strengthless material; we study the distribution of fragments and their water contents considering the full elasto-plastic continuum mechanics equations also including brittle failure and fragmentation.