Nice model

Nice model
en:User:AstroMark · CC BY-SA 3.0 · source
Name	Nice model
Author	Morbidelli et al.
Year	2005
Field	Planetary science

Nice model The Nice model proposes a dynamical scenario for the early Solar System in which interactions among the giant planets and a primordial planetesimal disk reorganized planetary orbits and produced major small-body populations. It links the orbital architecture of Jupiter, Saturn, Uranus, and Neptune to events such as the emplacement of the Kuiper belt, scattering that formed the Oort cloud, and delivery of impactors during the Late Heavy Bombardment. The model has been refined by researchers at institutions including the Observatoire de la Côte d'Azur, Southwest Research Institute, and University of Nice Sophia Antipolis and compared with alternatives from groups at California Institute of Technology and Massachusetts Institute of Technology.

Introduction

The Nice model originated to explain puzzling correlations among properties of Jupiter, Saturn, Uranus, Neptune, the Main asteroid belt, and distant reservoirs like the Kuiper belt and Oort cloud. It treats early Solar System evolution as a problem in planetary dynamics involving interactions with a massive planetesimal disk beyond the ice giants and resonant crossings between giant planets. Proponents tied the scenario to evidence from lunar samples returned by the Apollo program and geological interpretations of the Late Heavy Bombardment recorded on the Moon and terrestrial planets.

Origin and development

Development began in the early 2000s by researchers associated with the Observatoire de la Côte d'Azur and collaborators at University of Nice Sophia Antipolis, building on earlier work on planetesimal-driven migration by teams at NASA Ames Research Center and the Jet Propulsion Laboratory. Seminal papers synthesized numerical results from N-body integrators developed at University of Washington and Carnegie Institution for Science and incorporated constraints from observations by the Hubble Space Telescope, Keck Observatory, and Subaru Telescope. Subsequent improvements drew on computing resources at Los Alamos National Laboratory and software frameworks from Cornell University and Princeton University.

Mechanism and dynamical evolution

The model posits that after dissipation of the protoplanetary disk gas, the four giant planets interacted with a massive exterior planetesimal disk. Angular momentum exchange during planetesimal scattering caused outward migration of Uranus and Neptune and inward or slight outward shifts of Jupiter and Saturn. A key event is a resonance crossing between Jupiter and Saturn—typically the 1:2 mean-motion resonance—leading to dynamical instability, close encounters among the giants, and scattering of disk material. Numerical integrations using codes from Institut d'Astrophysique de Paris and Southwestern Research Institute show that this sequence can reproduce current semimajor axes, eccentricities, and inclinations of the giant planets while implanting planetesimals into the Main asteroid belt, Kuiper belt, and Oort cloud. The mechanism relies on conservation laws studied in works at Princeton Plasma Physics Laboratory and resonant dynamics frameworks from University of California, Berkeley.

Implications for the Solar System (giant planets, asteroid belt, Kuiper belt, Oort cloud)

For the giant planets, the model explains the present orbital spacing and the small but nonzero eccentricities and inclinations of Jupiter, Saturn, Uranus, and Neptune by invoking scattering and damping processes involving planetesimals. For the Main asteroid belt, resonant sweeping during planetary migration and implantation from the outer disk can account for compositional gradients observed by surveys with the Sloan Digital Sky Survey and spectroscopy from European Southern Observatory facilities. In the Kuiper belt, outward transport and resonant capture produce populations such as the plutinos in 2:3 resonance with Neptune and the classical belt's cold and hot components, as observed by the Canada–France–Hawaii Telescope and Pan-STARRS. The model also yields a mechanism for building the distant Oort cloud via strong scattering by the giant planets and subsequent galactic tides studied by researchers at Max Planck Institute for Solar System Research and Harvard–Smithsonian Center for Astrophysics.

Variants and refinements

Variants include the "jumping-Jupiter" scenario developed at University of Bern and Southwest Research Institute, which invokes planet-planet scattering with ejection of an ice giant to reduce sweeping of the inner Solar System; models with an extra primordial ice giant were explored by teams at University of Arizona and University of Chicago. Other refinements introduce self-gravitating planetesimal disks simulated at ETH Zurich and University of Pisa, collisional evolution from studies at Instituto de Astrofísica de Canarias, and gas-driven migration phases examined by groups at University of Cambridge and University of Toronto. Hybrid approaches combine elements from work at Dartmouth College and University of Copenhagen to reconcile timing constraints with crater records from the Lunar Reconnaissance Orbiter.

Observational evidence and constraints

Constraints come from spacecraft missions like Voyager 1, Voyager 2, and New Horizons that characterized outer Solar System bodies, telescopic surveys from Subaru Telescope and Keck Observatory that mapped small-body distributions, and isotopic analyses of samples related to the Apollo program and Genesis (spacecraft). Observational matches include resonant populations such as the plutinos and scattered disk objects cataloged by the Minor Planet Center, size distributions measured by the Herschel Space Observatory, and cratering records interpreted by scientists at Smithsonian Institution and Brown University. Isotopic and dynamical constraints from studies at Oxford University and California Institute of Technology set limits on the timing and severity of any instability.

Criticisms and alternative models

Criticisms address the robustness of reproducing terrestrial planet stability, the precise timing of the instability relative to lunar chronology, and the need for fine-tuned disk masses and damping. Alternative explanations include planetesimal-driven migration without late instability advocated by researchers at Université Paris Cité and models emphasizing in situ formation of Kuiper belt subpopulations proposed by teams at University of British Columbia and University of Maryland. Other alternatives derive from capture of planetesimals during stellar encounters studied by groups at University of St Andrews and McMaster University.

Category:Planetary science models