Collisionless encounters and the origin of the lunar inclination

  title={Collisionless encounters and the origin of the lunar inclination},
  author={Kaveh Pahlevan and Alessandro Morbidelli},
The Moon is generally thought to have formed from the debris ejected by the impact of a planet-sized object with the proto-Earth towards the end of planetary accretion. Models of the impact process predict that the lunar material was disaggregated into a circumplanetary disk and that lunar accretion subsequently placed the Moon in a near-equatorial orbit. Forward integration of the lunar orbit from this initial state predicts a modern inclination at least an order of magnitude smaller than the… 

Tidal evolution of the Moon from a high-obliquity, high-angular-momentum Earth

It is shown that tidal dissipation due to lunar obliquity was an important effect during the Moon’s tidal evolution, and the lunar inclination in the past must have been very large, defying theoretical explanations.

A multiple-impact origin for the Moon

The hypothesis of lunar origin by a single giant impact can explain some aspects of the Earth–Moon system. However, it is difficult to reconcile giant-impact models with the compositional similarity

Immediate Origin of the Moon as a Post-impact Satellite

The Moon is traditionally thought to have coalesced from the debris ejected by a giant impact onto the early Earth. However, such models struggle to explain the similar isotopic compositions of Earth

Tidal Evolution of the Earth–Moon System with a High Initial Obliquity

A giant-impact origin for the Moon is generally accepted, but many aspects of lunar formation remain poorly understood and debated. Ćuk et al. proposed that an impact that left the Earth–Moon system

Moonfalls: collisions between the Earth and its past moons

During the last stages of the terrestrial planet formation, planets grow mainly through giant-impacts with large planetary embryos. The Earth's Moon was suggested to form through one of these

Early Dynamics of the Lunar Core

The Moon is known to have a small liquid core, and it is thought that in the distant past the core may have produced strong magnetic fields recorded in lunar samples. Here we implement a numerical

The Origin of the Moon Within a Terrestrial Synestia

The giant impact hypothesis remains the leading theory for lunar origin. However, current models struggle to explain the Moon's composition and isotopic similarity with Earth. Here we present a new



Origin of the Moon's orbital inclination from resonant disk interactions

It is shown that the Moon's substantial orbital inclination is probably a natural result of its formation from an impact-generated disk, and involves a gravitational resonance between the Moon and accretion-disk material, which can increase orbital inclinations up to ∼15°.

Origin of the Moon in a giant impact near the end of the Earth's formation

This work reports a class of impacts that yield an iron-poor Moon, as well as the current masses and angular momentum of the Earth–Moon system, and suggests that the Moon formed near the very end of Earth's accumulation.

The lunar orbit revisited, III

In this paper we present an investigation on the tidal evolution of a system of three bodies: the Earth, the Moon and the Sun. Equations are derived including dissipation in the planet caused by the


We use a hybrid numerical approach to simulate the formation of the Moon from an impact-generated disk, consisting of a fluid model for the disk inside the Roche limit and an N-body code to describe

A low mass for Mars from Jupiter’s early gas-driven migration

Simulation of the early Solar System shows how the inward migration of Jupiter to 1.5 au, and its subsequent outward migration, lead to a planetesimal disk truncated at 1’au; the terrestrial planets then form from this disk over the next 30–50 million years, with an Earth/Mars mass ratio consistent with observations.

Dynamics of Lunar Formation

▪ Abstract The giant impact theory is the leading hypothesis for the origin of the Moon. This review focuses on dynamical aspects of an impact-induced lunar formation, in particular those areas that

Lunar-forming impacts: processes and alternatives

  • R. Canup
  • Physics, Geology
    Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
  • 2014
The formation of a protolunar disc by a giant impact with the early Earth is discussed, focusing on two classes of impacts: canonical impacts and high-angular-momentum impacts, both of which require subsequent processes for consistency with the current Earth and Moon.

Tidal Dissipation in the Early Lunar Magma Ocean and its Role in the Evolution of the Earth-Moon System

Dissipation in the Earth drove the Moon outwards over time. As it did so, the Moon’s obliquity increased, reaching a maximum at the socalled Cassini state transition at a distance of ~30 Earth radii


Most scenarios for the formation of the Moon place the Moon near Earth in low-eccentricity orbit in the equatorial plane of Earth. We examine the dynamical evolution of the Earth-Moon system from