The thermal–orbital evolution of the Earth–Moon system with a subsurface magma ocean and fossil figure

Downey, B. G.; Nimmo, F.; Matsuyama, I.

doi:10.1016/j.icarus.2022.115257

Cited by 3 publications

(3 citation statements)

References 55 publications

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“…Hence we added several features and differential equations to provide PT solutions on Gyr‐time scale. The integration of the long‐term precession equations follows the classical work of MacDonald (1964), Goldreich (1966), and Mignard (1981), shown to capture the essential dynamics (e.g., Touma & Wisdom, 1994) and appropriate for a variety of applications (e.g., Atobe & Ida, 2007; Cheng et al., 2014; Downey et al., 2023), as well as the current one (see below).…”

Section: Precession‐tilt Solutions and Frameworkmentioning

confidence: 99%

“…The current approach provides combined OS and PT solutions, the latter of which are obtained within a theoretical framework (Framework I hereafter) that has been applied to the Earth‐Moon system, Pluto‐Charon, exoplanets, etc. (e.g., MacDonald, 1964; Goldreich, 1966; Mignard, 1981; Touma & Wisdom, 1994; Atobe & Ida, 2007; Cheng et al, 2014; Downey et al, 2023). The emphasis is on long‐term physical solutions for the planetary spin axis, the satellite's orbital inclination, and (here) explicit obliquity and precession solutions.…”

Section: Precession‐tilt Solutions and Frameworkmentioning

confidence: 99%

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Milanković Forcing in Deep Time

Zeebe,

Lantink

2024

Paleoceanog and Paleoclimatol

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Astronomical (or Milanković) forcing of the Earth system is key to understanding rhythmic climate change on time scales ≳104 y. Paleoceanographic and paleoclimatological applications concerned with past astronomical forcing rely on astronomical calculations (solutions), which represent the backbone of cyclostratigraphy and astrochronology. Here we present state‐of‐the‐art astronomical solutions over the past 3.5 Gyr. Our goal is to provide tuning targets and templates for interpreting deep‐time cyclostratigraphic records and designing external forcing functions in climate models. Our approach yields internally consistent orbital and precession‐tilt solutions, including fundamental solar system frequencies, orbital eccentricity and inclination, lunar distance, luni‐solar precession rate, Earth's obliquity, and climatic precession. Contrary to expectations, we find that the long eccentricity cycle (LEC) (previously assumed stable and labeled “metronome,” recent period ∼405 kyr), can become unstable on long time scales. Our results reveal episodes during which the LEC is very weak or absent and Earth's orbital eccentricity and climate‐forcing spectrum are unrecognizable compared to the recent past. For the ratio of eccentricity‐to‐inclination amplitude modulation (recent individual periods of ~2.4 and ~1.2 Myr, frequently observable in paleorecords) we find a wide distribution around the recent 2:1 ratio, that is, the system is not restricted to a 2:1 or 1:1 resonance state. Our computations show that Earth's obliquity was lower and its amplitude (variation around the mean) significantly reduced in the past. We therefore predict weaker climate forcing at obliquity frequencies in deep time and a trend toward reduced obliquity power with age in stratigraphic records. For deep‐time stratigraphic and modeling applications, the orbital parameters of our 3.5‐Gyr integrations are made available at 400‐year resolution.

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Section: Precession‐tilt Solutions and Frameworkmentioning

confidence: 99%

Section: Precession‐tilt Solutions and Frameworkmentioning

confidence: 99%

Milanković Forcing in Deep Time

Zeebe,

Lantink

2024

Paleoceanog and Paleoclimatol

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“…The amount of angular momentum removed by the LPT depends on the Earth's initial obliquity and in the most extreme cases can reduce the initial angular momentum by a factor of 2 to 3. While the LPT requires an early Earth with a very large obliquity, such an obliquity is supported by several independent studies (Daher et al 2021;Downey et al 2023). Thus, given the narrow range of post-impact states required for the evection resonances and LPT, a particular difficulty of lunar formation theory continues to be the identification of a giant impact scenario that can simultaneously reproduce the angular momentum budget of the Earth-Moon system and the isotopic similarity of the Moon and Earth's mantle.…”

Section: Introductionmentioning

confidence: 96%

A Systematic Survey of Moon-forming Giant Impacts. I. Nonrotating Bodies

Timpe,

Reinhardt,

Meier

et al. 2023

ApJ

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In the leading theory of lunar formation, known as the giant impact hypothesis, a collision between two planet-size objects resulted in a young Earth surrounded by a circumplanetary debris disk from which the Moon later accreted. The range of giant impacts that could conceivably explain the Earth–Moon system is limited by the set of known physical and geochemical constraints. However, while several distinct Moon-forming impact scenarios have been proposed—from small, high-velocity impactors to low-velocity mergers between equal-mass objects—none of these scenarios have been successful at explaining the full set of known constraints, especially without invoking controversial post-impact processes. In order to bridge the gap between previous studies and provide a consistent survey of the Moon-forming impact parameter space, we present a systematic study of simulations of potential Moon-forming impacts. In the first paper of this series, we focus on pairwise impacts between nonrotating bodies. Notably, we show that such collisions require a minimum initial angular momentum budget of approximately 2 J EM in order to generate a sufficiently massive protolunar disk. We also show that low-velocity impacts (v ∞ ≲ 0.5 v esc) with high impactor-to-target mass ratios (γ → 1) are preferred to explain the Earth–Moon isotopic similarities. In a follow-up paper, we consider impacts between rotating bodies at various mutual orientations.

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Tidally driven remelting around 4.35 billion years ago indicates the Moon is old

Nimmo,

Kleine,

Morbidelli

2024

Nature

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The last giant impact on Earth is thought to have formed the Moon1. The timing of this event can be determined by dating the different rocks assumed to have crystallized from the lunar magma ocean (LMO). This has led to a wide range of estimates for the age of the Moon between 4.35 and 4.51 billion years ago (Ga), depending on whether ages for lunar whole-rock samples2–4 or individual zircon grains5–7 are used. Here we argue that the frequent occurrence of approximately 4.35-Ga ages among lunar rocks and a spike in zircon ages at about the same time8 is indicative of a remelting event driven by the Moon’s orbital evolution rather than the original crystallization of the LMO. We show that during passage through the Laplace plane transition9, the Moon experienced sufficient tidal heating and melting to reset the formation ages of most lunar samples, while retaining an earlier frozen-in shape10 and rare, earlier-formed zircons. This paradigm reconciles existing discrepancies in estimates for the crystallization time of the LMO, and permits formation of the Moon within a few tens of million years of Solar System formation, consistent with dynamical models of terrestrial planet formation11. Remelting of the Moon also explains the lower number of lunar impact basins than expected12,13, and allows metal from planetesimals accreted to the Moon after its formation to be removed to the lunar core, explaining the apparent deficit of such materials in the Moon compared with Earth14.

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The thermal–orbital evolution of the Earth–Moon system with a subsurface magma ocean and fossil figure

Cited by 3 publications

References 55 publications

Milanković Forcing in Deep Time

Milanković Forcing in Deep Time

A Systematic Survey of Moon-forming Giant Impacts. I. Nonrotating Bodies

Tidally driven remelting around 4.35 billion years ago indicates the Moon is old

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