scholarly journals Large impact cratering during lunar magma ocean solidification

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
K. Miljković ◽  
M. A. Wieczorek ◽  
M. Laneuville ◽  
A. Nemchin ◽  
P. A. Bland ◽  
...  
Keyword(s):  
The Moon ◽  
Magma Ocean ◽  
Impact Cratering ◽  
Low Viscosity ◽  
Impact Flux ◽  
Lunar Samples ◽  
History Of ◽  
Lunar Evolution ◽  
Asteroid Dynamics ◽  
Lunar Basins

AbstractThe lunar cratering record is used to constrain the bombardment history of both the Earth and the Moon. However, it is suggested from different perspectives, including impact crater dating, asteroid dynamics, lunar samples, impact basin-forming simulations, and lunar evolution modelling, that the Moon could be missing evidence of its earliest cratering record. Here we report that impact basins formed during the lunar magma ocean solidification should have produced different crater morphologies in comparison to later epochs. A low viscosity layer, mimicking a melt layer, between the crust and mantle could cause the entire impact basin size range to be susceptible to immediate and extreme crustal relaxation forming almost unidentifiable topographic and crustal thickness signatures. Lunar basins formed while the lunar magma ocean was still solidifying may escape detection, which is agreeing with studies that suggest a higher impact flux than previously thought in the earliest epoch of Earth-Moon evolution.

Geological Characteristics of the Moon

2020 ◽  
Author(s):  
Long Xiao ◽  
James W. Head
Keyword(s):  
The Moon ◽  
Planetary Evolution ◽  
Geological Characteristics ◽  
Lunar Interior ◽  
Geological Processes ◽  
Sequence Of Events ◽  
Geological Features ◽  
History Of ◽  
Lunar Evolution ◽  
Human Exploration

The geological characteristics of the Moon provide the fundamental data that permit the study of the geological processes that have formed and modified the crust, that record the state and evolution of the lunar interior, and that identify the external processes that have been important in lunar evolution. Careful documentation of the stratigraphic relationships among these features can then be used to reconstruct the sequence of events and the geological history of the Moon. These results can then be placed in the context of the geological evolution of the terrestrial planets, including Earth. The Moon’s global topography and internal structures include landforms and features that comprise the geological characteristics of its surface. The Moon is dominated by the ancient cratered highlands and the relatively younger flat and smooth volcanic maria. Unlike the current geological characteristics of Earth, the major geological features of the Moon (impact craters and basins, lava flows and related features, and tectonic scarps and ridges) all formed predominantly in the first half of the solar system’s history. In contrast to the plate-tectonic dominated Earth, the Moon is composed of a single global lithospheric plate (a one-plate planet) that has preserved the record of planetary geological features from the earliest phases of planetary evolution. Exciting fundamental outstanding questions form the basis for the future international robotic and human exploration of the Moon.

Electron Microprobe Analysis of Returned Lunar Samples

1970 ◽  
Vol 28 ◽  
pp. 18-19
Author(s):  
Klaus Keil
Keyword(s):  
Electron Microprobe ◽  
Large Scale ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
The Moon ◽  
Lunar Samples ◽  
Lower Oxygen ◽  
History Of ◽  
Non Destructive ◽  
Origin Of The Moon

The principle of the electron microprobe analyzer is explained and the special advantages of the technique in the study of returned lunar samples is discussed. Emphasis is given to non-destructive in-situ quantitative elemental analysis of micron-sized volumes. Results of electron microprobe analyses of rocks, and fines returned to Earth by the Apollo 11 and 12 missions are presented. Data that have significance to hypotheses on the origin and history of the lunar surface in the vicinity of the Apollo 11 and 12 landing sites and the Moon as a whole are given. Evidence is presented for differentiation of the Moon on a large scale, internal melting, absence of hydrous phases, lower oxygen fugacities as compared to terrestrial rocks, impact origin of fines and breccias, and high age near 4.5 billion years. Existing models for the origin of the Moon are discussed in the light of the data obtained by electron microprobe analysis, and it is concluded that neither the fission model nor the classical chondritic model can adequately explain the origin of the Moon.

The vaporization behavior of carbon and hydrogen from the early global magma ocean

2021 ◽  
Author(s):  
Natalia Solomatova ◽  
Razvan Caracas
Keyword(s):  
First Principles ◽  
Atmospheric Pressure ◽  
Considerable Effect ◽  
Early Earth ◽  
The Moon ◽  
Magma Ocean ◽  
Cooling History ◽  
History Of ◽  
Carbon Molecules ◽  
Dense Atmosphere

<p>Estimating the fluxes and speciation of volatiles during the existence of a global magma ocean is fundamental for understanding the cooling history of the early Earth and for quantifying the volatile budget of the present day. Using first-principles molecular dynamics, we predict the vaporization rate of carbon and hydrogen at the interface between the magma ocean and the hot dense atmosphere, just after the Moon-forming impact. The concentration of carbon and the oxidation state of the melts affect the speciation of the vaporized carbon molecules (e.g., the ratio of carbon dioxide to carbon monoxide), but do not appear to affect the overall volatility of carbon. We find that carbon is rapidly devolatilized even under pressure, while hydrogen remains mostly dissolved in the melt during the devolatilization process of carbon. Thus, in the early stages of the global magma ocean, significantly more carbon than hydrogen would have been released into the atmosphere, and it is only after the atmospheric pressure decreased, that much of the hydrogen devolatilized from the melt. At temperatures of 5000 K (and above), we predict that bubbles in the magma ocean contained a significant fraction of silicate vapor, increasing with decreasing depths with the growth of the bubbles, affecting the transport and rheological properties of the magma ocean. As the temperature cooled, the silicate species condensed back into the magma ocean, leaving highly volatile atmophile species, such as CO<sub>2</sub> and H<sub>2</sub>O, as the dominant species in the atmosphere. Due to the greenhouse nature of CO<sub>2</sub>, its concentration in the atmosphere would have had a considerable effect on the cooling rate of the early Earth.</p>

Charged-particle track analysis, thermoluminescence and microcratering studies of lunar samples

1977 ◽  
Vol 285 (1327) ◽  
pp. 309-317 ◽  
Keyword(s):  
Storage Temperature ◽  
Lunar Regolith ◽  
Lunar Soil ◽  
Heavy Ion ◽  
Abundance Ratio ◽  
Temperature Cycle ◽  
The Moon ◽  
Lunar Samples ◽  
History Of ◽  
Track Analysis

Studies of lunar samples (from both Apollo and Luna missions) have been carried out, using the track analysis and thermoluminescence (t.l.) techniques, with a view to shedding light on the radiation and temperature histories of the Moon. In addition, microcraters in lunar glasses have been studied in order to elucidate the cosmic-dust impact history of the lunar regolith. In track studies, the topics discussed include the stabilizing effect of the thermal annealing of fossil tracks due to the lunar temperature cycle; the ‘radiation annealing’ of fresh heavy-ion tracks by large doses of protons (to simulate the effect of lunar radiation-damage on track registration); and correction factors for the anisotropic etching of crystals which are required in reconstructing the exposure history of lunar grains. An abundance ratio of ca. (1.1 + 0.3) x 10-3 has been obtained, by the differential annealing technique, for the nuclei beyond the iron group to those within that group in the cosmic rays incident on the Moon. The natural t.l. of lunar samples has been used to estimate their effective storage temperature and mean depth below the surface. A suite of samples from known depths in an artificial trench at the Apollo 17 site has been used to calculate the effective thermal conductivity and thermal wavelength of overlying lunar soil at various depths. The temperatures in the shadow of some Apollo 17 boulders, and the duration of the boulders’ presence in situ, have also been estimated from samples which have been kept refrigerated since their retrieval from the Moon. Natural and artificially produced microcraters have been studied with the following two main results : The dust-particle flux appears to have fallen off over a certain period of ca. 104-105 years (if the solar activity is assumed to be constant over that interval). Stones predominate in the large { ca . 2-10 um) diameter intervals, while irons outnumber stones at low diameters (ca . 1.0 um), in the micrometeorite flux incident on the Moon.

scholarly journals Magnesium stable isotopes support the lunar magma ocean cumulate remelting model for mare basalts

2018 ◽  
Vol 116 (1) ◽  
pp. 73-78 ◽  
Author(s):  
Fatemeh Sedaghatpour ◽  
Stein B. Jacobsen
Keyword(s):  
Isotopic Composition ◽  
Isotopic Fractionation ◽  
The Moon ◽  
Magma Ocean ◽  
Isotopic Analyses ◽  
Lunar Samples ◽  
Lunar Basalts ◽  
Mg Isotopes ◽  
Isotopic Variations ◽  
Mare Basalts

We report high-precision Mg isotopic analyses of different types of lunar samples including two pristine Mg-suite rocks (72415 and 76535), basalts, anorthosites, breccias, mineral separates, and lunar meteorites. The Mg isotopic composition of the dunite 72415 (δ25Mg = −0.140 ± 0.010‰, δ26Mg = −0.291 ± 0.018‰), the most Mg-rich and possibly the oldest lunar sample, may provide the best estimate of the Mg isotopic composition of the bulk silicate Moon (BSM). This δ26Mg value of the Moon is similar to those of the Earth and chondrites and reflects both the relative homogeneity of Mg isotopes in the solar system and the lack of Mg isotope fractionation by the Moon-forming giant impact. In contrast to the behavior of Mg isotopes in terrestrial basalts and mantle rocks, Mg isotopic data on lunar samples show isotopic variations among the basalts and pristine anorthositic rocks reflecting isotopic fractionation during the early lunar magma ocean (LMO) differentiation. Calculated evolutions of δ26Mg values during the LMO differentiation are consistent with the observed δ26Mg variations in lunar samples, implying that Mg isotope variations in lunar basalts are consistent with their origin by remelting of distinct LMO cumulates.

scholarly journals Lunar samples record an impact 4.2 billion years ago that may have formed the Serenitatis Basin

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Ana Černok ◽  
Lee F. White ◽  
Mahesh Anand ◽  
Kimberly T. Tait ◽  
James R. Darling ◽  
...  
Keyword(s):  
Atom Probe ◽  
Distribution Functions ◽  
Radiometric Dating ◽  
The Moon ◽  
Impact Cratering ◽  
Size Frequency Distribution ◽  
Lunar Samples ◽  
Lunar Impact ◽  
Absolute Age ◽  
Impact Simulations

AbstractImpact cratering on the Moon and the derived size-frequency distribution functions of lunar impact craters are used to determine the ages of unsampled planetary surfaces across the Solar System. Radiometric dating of lunar samples provides an absolute age baseline, however, crater-chronology functions for the Moon remain poorly constrained for ages beyond 3.9 billion years. Here we present U–Pb geochronology of phosphate minerals within shocked lunar norites of a boulder from the Apollo 17 Station 8. These minerals record an older impact event around 4.2 billion years ago, and a younger disturbance at around 0.5 billion years ago. Based on nanoscale observations using atom probe tomography, lunar cratering records, and impact simulations, we ascribe the older event to the formation of the large Serenitatis Basin and the younger possibly to that of the Dawes crater. This suggests the Serenitatis Basin formed unrelated to or in the early stages of a protracted Late Heavy Bombardment.

Craters and Tsunamis

Impact! ◽  
1996 ◽  
Author(s):  
Gerrit L. Verschuur
Keyword(s):  
Solar System ◽  
A Priori ◽  
Point Of View ◽  
The Moon ◽  
History Of ◽  
Lunar Craters ◽  
The 1960S ◽  
Near Earth Asteroids ◽  
Lunar Basins ◽  
Rare Situation

Until the lunar explorations began in earnest in the 1960s, the Barringer crater in Arizona was believed to be one of the few, if not the only, impact crater on earth. Before the moon landings, many scientists thought that lunar craters were volcanic in origin and that the moon might be covered in a layer of volcanic dust meters thick so that astronauts would sink up to their eyeballs when disembarking from their space capsules. A pleasant sense of relief greeted the news that the first unmanned lunar spacecraft did not disappear into the dust. For a century or more it was doubted that lunar craters were produced by impacts because it was assumed that such craters would seldom be circular. It seemed obvious that circular craters could only be produced by objects falling straight down, a rare situation, since meteorites are likely to approach from random directions, especially on the moon where there is no atmosphere to slow them down before impact. W. M. Smart in 1928 stated this explicitly: “Objections to lunar craters being caused by meteors is that the craters are round and there is no a priori reason why meteors should fall vertically and in no other direction.” He also shuddered at the notion that the impactors would have to be as large as asteroids to create the lunar basins. At about the same time, Thomas Chamberlin ruled out impacts on the moon because there was no evidence for an appropriate population of objects anywhere in the solar system that could have made the craters That was in 1928 when near-earth asteroids had not yet been found, and when little was known about the history of the moon or the formation of the solar system. Richard A. Proctor in 1896, however, had concluded that because so many meteors continued to fall to earth that the planet and the solar system were still forming. To him, this made more sense than to blame the formation of the planets on “the creative fiats of the Almighty.” There is merit to his point of view, because today’s bombardment merely represents a faint, ongoing manifestation of the process of accretion that assembled the planets in the first place.

scholarly journals A long-lived magma ocean on a young Moon

2020 ◽  
Vol 6 (28) ◽  
pp. eaba8949 ◽  
Author(s):  
M. Maurice ◽  
N. Tosi ◽  
S. Schwinger ◽  
D. Breuer ◽  
T. Kleine
Keyword(s):  
Thermal Conductivity ◽  
Partial Melting ◽  
Time Scale ◽  
Solidification Time ◽  
Heat Extraction ◽  
The Moon ◽  
Magma Ocean ◽  
Lunar Crust ◽  
Lunar Samples ◽  
Remarkable Agreement

A giant impact onto Earth led to the formation of the Moon, resulted in a lunar magma ocean (LMO), and initiated the last event of core segregation on Earth. However, the timing and temporal link of these events remain uncertain. Here, we demonstrate that the low thermal conductivity of the lunar crust combined with heat extraction by partial melting of deep cumulates undergoing convection results in an LMO solidification time scale of 150 to 200 million years. Combining this result with a crystallization model of the LMO and with the ages and isotopic compositions of lunar samples indicates that the Moon formed 4.425 ± 0.025 billion years ago. This age is in remarkable agreement with the U-Pb age of Earth, demonstrating that the U-Pb age dates the final segregation of Earth’s core.

scholarly journals Constraining the Evolutionary History of the Moon and the Inner Solar System: A Case for New Returned Lunar Samples

2019 ◽  
Vol 215 (8) ◽  
Author(s):  
Romain Tartèse ◽  
Mahesh Anand ◽  
Jérôme Gattacceca ◽  
Katherine H. Joy ◽  
James I. Mortimer ◽  
...  
Keyword(s):  
Solar System ◽  
Large Scale ◽  
Lunar Regolith ◽  
The Moon ◽  
Planetary Body ◽  
The Past ◽  
Lunar Samples ◽  
History Of ◽  
Magma Oceans ◽  
Robotic Missions

AbstractThe Moon is the only planetary body other than the Earth for which samples have been collected in situ by humans and robotic missions and returned to Earth. Scientific investigations of the first lunar samples returned by the Apollo 11 astronauts 50 years ago transformed the way we think most planetary bodies form and evolve. Identification of anorthositic clasts in Apollo 11 samples led to the formulation of the magma ocean concept, and by extension the idea that the Moon experienced large-scale melting and differentiation. This concept of magma oceans would soon be applied to other terrestrial planets and large asteroidal bodies. Dating of basaltic fragments returned from the Moon also showed that a relatively small planetary body could sustain volcanic activity for more than a billion years after its formation. Finally, studies of the lunar regolith showed that in addition to containing a treasure trove of the Moon’s history, it also provided us with a rich archive of the past 4.5 billion years of evolution of the inner Solar System. Further investigations of samples returned from the Moon over the past five decades led to many additional discoveries, but also raised new and fundamental questions that are difficult to address with currently available samples, such as those related to the age of the Moon, duration of lunar volcanism, the lunar paleomagnetic field and its intensity, and the record on the Moon of the bombardment history during the first billion years of evolution of the Solar System. In this contribution, we review the information we currently have on some of the key science questions related to the Moon and discuss how future sample-return missions could help address important knowledge gaps.

scholarly journals Crustal porosity reveals the bombardment history of the Moon

2021 ◽  
Author(s):  
Ya Huei Huang ◽  
Jason Soderblom ◽  
David Minton ◽  
Masatoshi Hirabayashi ◽  
Jay Melosh
Keyword(s):  
Solar System ◽  
Surface Expression ◽  
Orbital Evolution ◽  
Terrestrial Planets ◽  
The Moon ◽  
Planetary Evolution ◽  
History Of ◽  
Giant Impacts ◽  
Formation And Evolution ◽  
Lunar Basins

Abstract Planetary bombardment histories provide critical information regarding the formation and evolution of the Solar System and of the planets within it. These records evidence transient instabilities in the Solar System’s orbital evolution, giant impacts such as the Moon-forming impact, and material redistribution. Such records provide insight into planetary evolution, including the deposition of energy, delivery of materials, and crustal processing, specifically the modification of porosity. Bombardment histories are traditionally constrained from the surface expression of impacts — these records, however, are degraded by various geologic processes. Here we show that the Moon’s porosity contains a more complete record of its bombardment history. We find that the terrestrial planets were subject to double the number of ≥20-km-diameter-crater-forming impacts than are recorded on the lunar highlands, fewer than previously thought to have occurred. We show that crustal porosity doesn’t slowly increase as planets evolve, but instead is generated early in a planet’s evolution when most basins formed and decreases as planets evolve. We show that porosity constrains the relative ages of basins formed early in a planet’s evolution, a timeframe for which little information exists. These findings demonstrate that the Solar System was less violent than previously thought. Fewer volatiles and other materials were delivered to the terrestrial planets, consistent with estimates of the delivery of siderophiles and water to the Moon. High crustal porosity early in the terrestrial planets’ evolution slowed their cooling and enhanced their habitability. Several lunar basins formed early than previously considered, casting doubt on the existence of a late heavy bombardment.

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