Open questions in lunar science (invited talk)

2021 ◽  
Author(s):  
James Head
Keyword(s):  
Solar System ◽  
Planetary Science ◽  
Lunar Exploration ◽  
The Moon ◽  
Origin And Evolution ◽  
Lunar Science ◽  
The Earth ◽  
Planetary Bodies ◽  
Over Time

<p>The Earth’s Moon is a cornerstone and keystone in the understanding of the origin and evolution of the terrestrial, Earth-like planets.  It is a cornerstone in that most of the other paradigms for the origin, modes of crustal formation (primary, secondary and tertiary), bombardment history, role of impact craters and basins in shaping early planetary surfaces and fracturing and modifying the crust and upper mantle, volcanism and the formation of different types of secondary crust, and petrogenetic models where no samples are available, all have a fundamental foundation in lunar science.  The Moon is a keystone in that knowledge of the Moon holds upright the arch of our understand of the terrestrial planets. It is thus imperative to dedicate significant resources to the continued robotic and human exploration of this most accessible of other terrestrial planetary bodies, and to use this cornerstone and keystone as a way to frame critical questions about the Solar System as a whole, and to explore other planetary bodies to modify and strengthen the lunar paradigm.   </p> <p>What is the legacy, the long-term impact of our efforts? The Apollo Lunar Exploration Program revealed the Earth as a planet, showed the inextricable links of the Earth-Moon system, and made the Solar System our neighborhood. We now ask: What are our origins and where are we heading?: We seek to understand the origin and evolution of the Moon, the Moon’s links to the earliest history of Earth, and its lessons for exploration and understanding of Mars and other terrestrial planets. A basis for our motivation is the innate human qualities of curiosity and exploration, and the societal/species-level need to heed Apollo 16 Commander John Young’s warning that “Single-planet species don’t survive!”. These perspectives impel us to learn the lessons of off-Earth, long-term, long-distance resupply and self-sustaining presence, in order to prepare for the exploration of Mars and other Solar System destinations. </p> <p>Key questions in this lunar exploration endeavor based on a variety of studies and analyses (1-3) include:</p> <p>-How do planetary systems form and evolve over time and when did major events in our Solar System occur?</p> <p>How did planetary interiors differentiate and evolve through time, and how are interior processes expressed through surface-atmosphere interactions?</p> <p>-What processes shape planetary surfaces and how do these surfaces record Solar System history?</p> <p>-How do worlds become habitable and how is habitability sustained over time?</p> <p>-Why are the atmospheres and climates of planetary bodies so diverse, and how did they evolve over time?</p> <p>-Is there life elsewhere in the Solar System?</p> <p>Specific lunar goals and objectives will be outlined in this broad planetary science context.</p> <p> </p> <p>References: 1. Carle Pieters et al. (2018) http://www.planetary.brown.edu/pdfs/5480.pdf, 2. Lunar Exploration Analysis Group, https://www.lpi.usra.edu/leag/. 3) Erica Jawin et al. Planetary Science Priorities for the Moon in the Decade 2023-2033: Lunar Science is Planetary Science.</p>

scholarly journals Advances in Cosmochemistry Enabled by Antarctic Meteorites

2020 ◽  
Vol 48 (1) ◽  
pp. 233-258
Author(s):  
Meenakshi Wadhwa ◽  
Timothy J. McCoy ◽  
Devin L. Schrader
Keyword(s):  
Solar System ◽  
Planetary Science ◽  
The Moon ◽  
Origin And Evolution ◽  
Lunar Meteorite ◽  
Planetary Bodies ◽  
The Antarctic ◽  
Melt Pockets ◽  
Scientific Advances

At present, meteorites collected in Antarctica dominate the total number of the world's known meteorites. We focus here on the scientific advances in cosmochemistry and planetary science that have been enabled by access to, and investigations of, these Antarctic meteorites. A meteorite recovered during one of the earliest field seasons of systematic searches, Elephant Moraine (EET) A79001, was identified as having originated on Mars based on the composition of gases released from shock melt pockets in this rock. Subsequently, the first lunar meteorite, Allan Hills (ALH) 81005, was also recovered from the Antarctic. Since then, many more meteorites belonging to these two classes of planetary meteorites, as well as other previously rare or unknown classes of meteorites (particularly primitive chondrites and achondrites), have been recovered from Antarctica. Studies of these samples are providing unique insights into the origin and evolution of the Solar System and planetary bodies. ▪  Antarctic meteorites dominate the inventory of the world's known meteorites and provide access to new types of planetary and asteroidal materials. ▪  The first meteorites recognized to be of lunar and martian origin were collected from Antarctica and provided unique constraints on the evolution of the Moon and Mars. ▪  Previously rare or unknown classes of meteorites have been recovered from Antarctica and provide new insights into the origin and evolution of the Solar System.

scholarly journals Lunar exploration: opening a window into the history and evolution of the inner Solar System

2014 ◽  
Vol 372 (2024) ◽  
pp. 20130315 ◽  
Author(s):  
Ian A. Crawford ◽  
Katherine H. Joy
Keyword(s):  
Solar System ◽  
Lunar Exploration ◽  
The Moon ◽  
Moon System ◽  
Origin And Evolution ◽  
The Earth ◽  
Geological Evolution ◽  
History Of ◽  
Rocky Planets

The lunar geological record contains a rich archive of the history of the inner Solar System, including information relevant to understanding the origin and evolution of the Earth–Moon system, the geological evolution of rocky planets, and our local cosmic environment. This paper provides a brief review of lunar exploration to-date and describes how future exploration initiatives will further advance our understanding of the origin and evolution of the Moon, the Earth–Moon system and of the Solar System more generally. It is concluded that further advances will require the placing of new scientific instruments on, and the return of additional samples from, the lunar surface. Some of these scientific objectives can be achieved robotically, for example by in situ geochemical and geophysical measurements and through carefully targeted sample return missions. However, in the longer term, we argue that lunar science would greatly benefit from renewed human operations on the surface of the Moon, such as would be facilitated by implementing the recently proposed Global Exploration Roadmap.

New Economy in space: Cis-lunar economic circle and analogue simulations in China to the 2061 Horizon

2020 ◽  
Author(s):  
guo linli ◽  
blanc michel ◽  
huang tieqiu ◽  
huang jiangze ◽  
yuan jianping ◽  
...  
Keyword(s):  
International Cooperation ◽  
Lunar Surface ◽  
Space Exploration ◽  
Shaanxi Province ◽  
Lunar Exploration ◽  
Test Field ◽  
The Moon ◽  
Liquid Propellant ◽  
The Earth

<p>    The Moon is sometimes also called the "eighth continent" of the Earth. Determining how to utilize cis-lunar orbital infrastructures and lunar resources to carry out new economic activities extended to the space of the Earth-Moon system is one of the long-term goals of lunar exploration activities around the world. Future long-term human deep-space exploration missions to the Moon, on the Moon surface or using the Moon to serve farther destinations will require the utilization of lunar surface or asteroid resources to produce water, oxygen and other consumables needed to maintain human survival and to produce liquid propellant for the supply of spacecraft on the lunar surface. In complement to exploration activities, Moon tourism in cis-lunar orbit and on the lunar surface will become more and more attractive with the increase of  human spaceflight capacity and the development of commercial space activities. However, the development of a sustainable Earth-Moon ecosystem requires that we solve the following five problems:</p><p>(1)How to design alow-cost cis-lunar space transportation capacity? To find an optimal solution, one must compare direct Earth-Moon flight modes with flights based on the utilization of space stations, and identify the most economical spacecraft architectures.</p><p>(2)How to design an efficient set ofcis-lunar orbital infrastructures combining LEO space stations, Earth-Moon L1/L2 point space stations and Moon bases for commercial tourism, taking into account key issues such as energy, communications and others?</p><p>(3)Significant amounts ofliquid oxygen, water, liquid propellant and structural material will be needed for human bases, crew environmental control and life support systems, spacecraft propulsion systems, Moon surface storage and transportation systems. How to  design in-situ resources utilization (ISRU) of the Moon, including its soil, rocks and polar water ice reservoirs, to produce the needed amounts?</p><p>(4) How to simulate on the Earth surface the different components and key technologies that will enable a future long-term human residence on the Moon surface?</p><p>(5). How to accommodate the co-development of public and commercial space and foster international cooperation? How can space policies and international space law help this co-development?</p><p>    China has made rapid progress in robotic lunar exploration activities in the last 20 years, as illustrated by the recent discoveries provided by the Chang'e-4 lander on the far side of the Moon. By 2061, China will have gone into manned lunar exploration and built Moon bases. In preparation for this new phase of its contribution to space exploration, lunar surface simulation instruments have been built in Beijing, Shenzhen and other places in China. A series of achievements have been made in the field of space life sciences . An ambitious project to establish a large Moon base simulation test field, the Lunar Base Yulin (LBY) project, currently in its design phase in Yulin, Shaanxi Province in China, will allow the verification of key relevant technologies.</p><p>    By the 2061 Horizon, we believe that international cooperation and public-private partnership will be key elements to enable this vision of a new, sustainable cis-lunar space economy.</p>

The Origin of the Moon

1962 ◽  
Vol 14 ◽  
pp. 149-155 ◽  
Author(s):  
E. L. Ruskol
Keyword(s):  
Chemical Composition ◽  
Solar System ◽  
The Moon ◽  
The Earth ◽  
The Difference ◽  
Origin Of The Moon

The difference between average densities of the Moon and Earth was interpreted in the preceding report by Professor H. Urey as indicating a difference in their chemical composition. Therefore, Urey assumes the Moon's formation to have taken place far away from the Earth, under conditions differing substantially from the conditions of Earth's formation. In such a case, the Earth should have captured the Moon. As is admitted by Professor Urey himself, such a capture is a very improbable event. In addition, an assumption that the “lunar” dimensions were representative of protoplanetary bodies in the entire solar system encounters great difficulties.

The Origin of the Moon and its Relationship to the Origin of the Solar System

1962 ◽  
Vol 14 ◽  
pp. 133-148 ◽  
Author(s):  
Harold C. Urey
Keyword(s):  
Solar System ◽  
The Moon ◽  
The Past ◽  
The Earth ◽  
Short Period ◽  
Origin Of The Moon

During the last 10 years, the writer has presented evidence indicating that the Moon was captured by the Earth and that the large collisions with its surface occurred within a surprisingly short period of time. These observations have been a continuous preoccupation during the past years and some explanation that seemed physically possible and reasonably probable has been sought.

scholarly journals Isotopic evidence for the formation of the Moon in a canonical giant impact

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sune G. Nielsen ◽  
David V. Bekaert ◽  
Maureen Auro
Keyword(s):  
Solar System ◽  
Isotope Fractionation ◽  
Main Stage ◽  
The Moon ◽  
Giant Impact ◽  
Bulk Silicate Earth ◽  
The Earth ◽  
The Standard Model ◽  
Isotopic Measurements ◽  
Origin Of The Moon

AbstractIsotopic measurements of lunar and terrestrial rocks have revealed that, unlike any other body in the solar system, the Moon is indistinguishable from the Earth for nearly every isotopic system. This observation, however, contradicts predictions by the standard model for the origin of the Moon, the canonical giant impact. Here we show that the vanadium isotopic composition of the Moon is offset from that of the bulk silicate Earth by 0.18 ± 0.04 parts per thousand towards the chondritic value. This offset most likely results from isotope fractionation on proto-Earth during the main stage of terrestrial core formation (pre-giant impact), followed by a canonical giant impact where ~80% of the Moon originates from the impactor of chondritic composition. Our data refute the possibility of post-giant impact equilibration between the Earth and Moon, and implies that the impactor and proto-Earth mainly accreted from a common isotopic reservoir in the inner solar system.

scholarly journals Bayesian constraints on the origin and geology of exo-planetary material using a population of externally polluted white dwarfs

2021 ◽  
Author(s):  
John H D Harrison ◽  
Amy Bonsor ◽  
Mihkel Kama ◽  
Andrew M Buchan ◽  
Simon Blouin ◽  
...  
Keyword(s):  
Solar System ◽  
White Dwarf ◽  
Bayesian Model ◽  
Total Mass ◽  
White Dwarfs ◽  
Bulk Composition ◽  
Planetary Systems ◽  
The Moon ◽  
Planetary Bodies ◽  
Nearby Stars

Abstract White dwarfs that have accreted planetary bodies are a powerful probe of the bulk composition of exoplanetary material. In this paper, we present a Bayesian model to explain the abundances observed in the atmospheres of 202 DZ white dwarfs by considering the heating, geochemical differentiation, and collisional processes experienced by the planetary bodies accreted, as well as gravitational sinking. The majority (>60%) of systems are consistent with the accretion of primitive material. We attribute the small spread in refractory abundances observed to a similar spread in the initial planet-forming material, as seen in the compositions of nearby stars. A range in Na abundances in the pollutant material is attributed to a range in formation temperatures from below 1,000 K to higher than 1,400 K, suggesting that pollutant material arrives in white dwarf atmospheres from a variety of radial locations. We also find that Solar System-like differentiation is common place in exo-planetary systems. Extreme siderophile (Fe, Ni or Cr) abundances in 8 systems require the accretion of a core-rich fragment of a larger differentiated body to at least a 3σ significance, whilst one system shows evidence that it accreted a crust-rich fragment. In systems where the abundances suggest that accretion has finished (13/202), the total mass accreted can be calculated. The 13 systems are estimated to have accreted masses ranging from the mass of the Moon to half that of Vesta. Our analysis suggests that accretion continues for 11Myrs on average.

Late Accretion and the Origin of Water on Terrestrial Planets in the Solar System

2021 ◽  
Author(s):  
Cédric Gillmann ◽  
Gregor Golabek ◽  
Sean Raymond ◽  
Paul Tackley ◽  
Maria Schonbachler ◽  
...  
Keyword(s):  
Solar System ◽  
Long Term Evolution ◽  
Terrestrial Planets ◽  
Evolutionary Pathway ◽  
Giant Impact ◽  
The Earth ◽  
Term Evolution ◽  
Surface Liquid ◽  
Venus Atmosphere

<p>Terrestrial planets in the Solar system generally lack surface liquid water. Earth is at odd with this observation and with the idea of the giant Moon-forming impact that should have vaporized any pre-existing water, leaving behind a dry Earth. Given the evidence available, this means that either water was brought back later or the giant impact could not vaporize all the water.</p><p>We have looked at Venus for answers. Indeed, it is an example of an active planet that may have followed a radically different evolutionary pathway despite the similar mechanisms at work and probably comparable initial conditions. However, due to the lack of present-day plate tectonics, volatile recycling, and any surface liquid oceans, the evolution of Venus has likely been more straightforward than that of the Earth, making it easier to understand and model over its long term evolution.</p><p>Here, we investigate the long-term evolution of Venus using self-consistent numerical models of global thermochemical mantle convection coupled with both an atmospheric evolution model and a late accretion N-body delivery model. We test implications of wet and dry late accretion compositions, using present-day Venus atmosphere measurements. Atmospheric losses are only able to remove a limited amount of water over the history of the planet. We show that late accretion of wet material exceeds this sink. CO<sub>2</sub> and N<sub>2</sub> contributions serve as additional constraints.</p><p>Water-rich asteroids colliding with Venus and releasing their water as vapor cannot explain the composition of Venus atmosphere as we measure it today. It means that the asteroidal material that came to Venus, and thus to Earth, after the giant impact must have been dry (enstatite chondrites), therefore preventing the replenishment of the Earth in water. Because water can obviously be found on our planet today, it means that the water we are now enjoying on Earth has been there since its formation, likely buried deep in the Earth so it could survive the giant impact. This in turn suggests that suggests that planets likely formed with their near-full budget in water, and slowly lost it with time.</p>

scholarly journals Remotely distinguishing and mapping endogenic water on the Moon

2017 ◽  
Vol 375 (2094) ◽  
pp. 20150391 ◽  
Author(s):  
Rachel L. Klima ◽  
Noah E. Petro
Keyword(s):  
Solar Wind ◽  
Spatial Distribution ◽  
Solar System ◽  
The Moon ◽  
Testing Hypotheses ◽  
Origin And Evolution ◽  
Lunar Interior ◽  
Geological Features ◽  
Insight Into

Water and/or hydroxyl detected remotely on the lunar surface originates from several sources: (i) comets and other exogenous debris; (ii) solar-wind implantation; (iii) the lunar interior. While each of these sources is interesting in its own right, distinguishing among them is critical for testing hypotheses for the origin and evolution of the Moon and our Solar System. Existing spacecraft observations are not of high enough spectral resolution to uniquely characterize the bonding energies of the hydroxyl molecules that have been detected. Nevertheless, the spatial distribution and associations of H, OH − or H 2 O with specific lunar lithologies provide some insight into the origin of lunar hydrous materials. The global distribution of OH − /H 2 O as detected using infrared spectroscopic measurements from orbit is here examined, with particular focus on regional geological features that exhibit OH − /H 2 O absorption band strengths that differ from their immediate surroundings. This article is part of the themed issue ‘The origin, history and role of water in the evolution of the inner Solar System’.

scholarly journals Features of the geochemistry of the Moon and the Earth, determined by the mechanism of formation of the Earth – Moon system (report at the 81st international meteorite conference, Moscow, july 2018)

2019 ◽  
Vol 64 (8) ◽  
pp. 762-776
Author(s):  
E. M. Galimov
Keyword(s):  
Solar System ◽  
Volatile Components ◽  
Kinetic Regime ◽  
The Moon ◽  
Mechanism Of Formation ◽  
Planetary Body ◽  
Moon System ◽  
The Earth ◽  
Reversible Nature ◽  
Dust Condensation

This article discusses some features of geochemistry of the Earth and the Moon, which manifests the specificity of the mechanism of their formation by fragmentation of protoplanetary gas-dust condensation (Galimov & Krivtsov, 2012). The principal difference between this model and other hypotheses of the Earth-Moon system formation, including the megaimpact hypothesis, is that it assumes the existence of a long stage of the dispersed state of matter, starting with the formation of protoplanetary gas-dust condensation, its compression and fragmentation and ending with the final accretion to the formed high-temperature embryos of the Earth and the Moon. The presence of the dispersed state allows a certain way to interpret the observed properties of the Earth-Moon system. Partial evaporation of solid particles due to adiabatic heating of the compressing condensation leads to the loss of volatiles including FeO. Computer simulations show that the final accretion is mainly performed on a larger fragment (the Earth’s embryo) and only slightly increases the mass of the smaller fragment (the Moon embryo).This explains the relative depletion of the Moon in iron and volatile and the increased concentration of refractory components compared to the Earth. The reversible nature of evaporation into the dispersed space, in contrast to the kinetic regime, and the removal of volatiles in the hydrodynamic flow beyond the gas-dust condensation determines the loss of volatiles without the effect of isotopes fractionation. The reversible nature of volatile evaporation also provides, in contrast to the kinetic regime, the preservation of part of the high-volatile components, such as water, in the planetary body, including the Moon. It follows from the essence of the model that at least a significant part of the Earth’s core is formed not by segregation of iron in the silicate-metal melt, but by evaporation and reduction of FeO in a dispersed medium, followed by deposition of clusters of elemental iron to the center of mass. This mechanism of formation of the core explains the observed excess of siderophilic elements in the Earth’s mantle. It also provides a plausible explanation for the observed character of iron isotopes fractionation (in terms of δ57Fe‰) on Earth and on the Moon. It solves the problem of the formation of iron core from initially oxide (FeO) form. The dispersed state of the substance during the period of accretion suggests that the loss of volatiles occurred during the time of accretion. Using the fact that isotopic systems: U–Pb, Rb–Sr, 129J–129Xe, 244Pu–136Xe, contain volatile components, it is possible to estimate the chronology of events in the evolution of the protoplanetary state. As a result, agreed estimates of the time of fragmentation of the primary protoplanetary condensation and formation of the embryos of the Earth and the Moon are obtained: from 10 to 40 million years, and the time of completion of the earth’s accretion and its birth as a planetary body: 110 – 130 million years after the emergence of the solar system. The presented interpretation is consistent with the fact that solid minerals on the Moon have already appeared at least 60 million years after the birth of the solar system (Barboni et al., 2017), and the metal core in the Earth and in the Moon could not have formed before 50 million years from the start of the solar system, as follows from the analysis of the Hf-W system (Kleine et al., 2009). It is shown that the hypothesis of megaimpact does not satisfy many constraints and does not create a basis for the explanation of the geochemistry of the Earth and the Moon.

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