Earth wind as a possible source of lunar surface hydration
H. Z. Wang, J. Zhang, Q. Q. Shi, Y. Saito, A. W. Degeling, I. J. Rae, J. Liu, R. L. Guo, Z. H. Yao, A. M. Tian, X. H. Fu, Q. G. Zong, J. Z. Liu, Z. C. Ling, W. … 展开作者
H. Z. Wang, J. Zhang, Q. Q. Shi, Y. Saito, A. W. Degeling, I. J. Rae, J. Liu, R. L. Guo, Z. H. Yao, A. M. Tian, X. H. Fu, Q. G. Zong, J. Z. Liu, Z. C. Ling, W. J. Sun, S. C. Bai, J. Chen, S. T. Yao, H. Zhang, Y. Wei, W. L. Liu, L. D. Xia, Y. Chen, Y. Y. Feng, S. Y. Fu, Z. Y. Pu
Understanding the sources of lunar water is crucial for studying the history of lunar evolution, and also the solar wind interaction with the Moon and other airless bodies. Recent observations revealed lunar hydration is very likely a surficial dynamic process driven by solar wind. Solar wind is shielded over a period of 3-5 days as the Moon passes through the Earth's magnetosphere, during which a significant loss of hydration is expected from previous works.Here we study lunar hydration inside the magnetosphere using orbital spectral data, which unexpectedly found that the polar surficial OH/H2O abundance remains at the same level when in the solar wind and in the magnetosphere. We suggest that particles from the magnetosphere (Earth wind, naturally different from solar wind) contribute to lunar hydration. From lunar orbital plasma observations, we find the existence of optimal energy ranges, other than 1 keV as previously thought, for surface hydration formation. These optimal energy ranges deduced from space observations may provide strong implications for laboratory experiments simulating lunar hydration processes.
The lunar farside highlands problem refers to the curious and unexplained fact that the farside lunar crust is thicker, on average, than the nearside crust. Here we recognize the crucial influence of Earthshine, and propose that it naturally explains this hemispheric dichotomy. Since the accreting Moon rapidly achieved synchronous rotation, a surface and atmospheric thermal gradient was imposed by the proximity of the hot, post-Giant-Impact Earth. This gradient guided condensation of atmospheric and accreting material, preferentially depositing crust-forming refractories on the cooler farside,…
This paper aims to obtain an analytic approximation to the evolution of circular orbits governed by the Earth's $J_2$ and the luni-solar gravitational perturbations. Assuming that the lunar orbital plane coincides with the ecliptic plane, Allan and Cook (1964) derived an analytic solution to the orbital plane evolution of circular orbits. Using their result as an intermediate solution, we establish an approximate analytic model with lunar orbital inclination and its node regression be taken into account. Finally, an approximate analytic expression is derived, which is accurate compared to the …
Lunar ejecta as the missing piece to resolve the lunar cratering asymmetry
State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology（澳门科技大学月球与行星科学国家重点实验室）；School of Astronomy and Space Science, Nanjing University（南京大学天文与空间科学学院）；Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education, Nanjing University（南京大学现代天文学与天体物理教育部重点实验室）
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. Modeling of the impact process predicts 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 lunar value, a long-standing discrepancy known as the lunar inclination problem. Here we show that…
Little is known about Earth quasi-satellites, a class of near-Earth small solar system bodies that orbit the sun but remain close to the Earth, because they are faint and difficult to observe. Here we use the Large Binocular Telescope (LBT) and the Lowell Discovery Telescope (LDT) to conduct a comprehensive physical characterization of quasi-satellite (469219) Kamo`oalewa and assess its affinity with other groups of near-Earth objects. We find that (469219) Kamo`oalewa rotates with a period of 28.3 (+1.8/-1.3) minutes and displays a reddened reflectance spectrum from 0.4-2.2 microns. This spec…
The steady-state population of Earth's co-orbitals of lunar provenance
Istituto di Matematica Applicata e Tecnologie Informatiche, Consiglio Nazionale delle Ricerche (IMATI-CNR)（应用数学与信息技术研究所，意大利国家研究委员会）；Institute for Astronomy, University of Hawai‘i（天文学研究所，夏威夷大学）
With the rapid developments in the exoplanet field, more and more terrestrial exoplanets are being detected. Characterising their atmospheres using transit observations will become a key datum in the quest for detecting an Earth-like exoplanet. The atmospheric transmission spectrum of our Earth will be an ideal template for comparison with future exo-Earth candidates. By observing a lunar eclipse, which offers a similar configuration to that of an exoplanet transit, we have obtained a high resolution and high signal-to-noise ratio transmission spectrum of the Earth's atmosphere. This observati…
Polarization during a lunar eclipse is a forgotten mystery. Coyne & Pellicori (1970) reported the detection of significant polarization during the lunar eclipse on 1968 April 13. Multiple scattering during the first transmission through the Earth's atmosphere was suggested as a possible cause of the polarization, but no conclusive determination was made. No further investigations on polarization during a lunar eclipse are known. We revisit this mystery with an interest in possible application to extrasolar planets, if planetary transmitted light is indeed polarized, it may be possible to inves…
Many science missions require an unobstructed view of space and a stable thermal environment but lack the technical or programmatic resources to reach orbits that satisfy these needs. This paper presents a high Earth orbit in 2:1 resonance with the Moon that provides these conditions, reached via lunar gravity assist. Analytical guidance and numerical investigation yielded deep insight into this unconventional orbit's behavior, making it possible to select a robust mission design. Solutions are available for a broad range of missions, from smaller Explorer-class missions such as the Transiting…
We examine how water is produced globally over the lunar surface as it orbits in/out of the magnetotail. Due to the interaction of the solar wind (SW) with Earth's magnetic field, upstream the magnetic field is compressed down to ~10 Earth radii. However, the diverted stream of SW around Earth's magnetic field results in an extended depleted region of SW protons (positively charged hydrogen) out to 1000's of Earth radii, referred to as the magnetotail. The Moon orbits at a distance of ~40 Earth radii; therefore, upstream it is within the SW, but downstream it is partially shielded while in the…
Lunar dust particles are generated by hypervelocity impacts of interplanetary micron-meteoroids onto the surface of the Moon, which seriously threatens the security of explorations. Studying the lunar dust dynamics helps to understand the origin and migration mechanism of lunar dust, and to provide the theoretical guidelines for the orbital design of lunar space missions. This paper reviews previous research on the lunar dust dynamics, including the interplanetary impactor environment at the Earth-Moon system, the mass production rate, the initial mass, speed and ejecta angle distributions, th…
If properly interpreted, the impact record of the Moon, Earth's nearest neighbour, can be used to gain insights into how the Earth has been influenced by impacting events since its formation ~4.5 billion years (Ga) ago. However, the nature and timing of the lunar impactors - and indeed the lunar impact record itself - are not well understood. Of particular interest are the ages of lunar impact basins and what they tell us about the proposed "lunar cataclysm" and/or the late heavy bombardment (LHB), and how this impact episode may have affected early life on Earth or other planets. Investigatio…
Despite its importance to questions of lunar origin, the chemical composition of the Moon is not precisely known. In recent years, however, the isotopic composition of lunar samples has been determined to high precision and found to be indistinguishable from the terrestrial mantle despite widespread isotopic heterogeneity in the Solar System. In the context of the giant-impact hypothesis, this level of isotopic homogeneity can evolve if the proto-lunar disk and post-impact Earth undergo turbulent mixing into a single uniform reservoir while the system is extensively molten and partially vapori…
It is known that most of the craters on the surface of the Moon were created by the collision of minor bodies of the Solar System. Main Belt Asteroids, which can approach the terrestrial planets as a consequence of different types of resonance, are actually the main responsible for this phenomenon. Our aim is to investigate the impact distributions on the lunar surface that low-energy dynamics can provide. As a first approximation, we exploit the hyberbolic invariant manifolds associated with the central invariant manifold around the equilibrium point L_2 of the Earth - Moon system within the …
Simulations of the moon-forming impact suggest that most of the lunar material derives from the impactor rather than the Earth. Measurements of lunar samples, however, reveal an oxygen isotope composition that is indistinguishable from terrestrial samples, and clearly distinct from meteorites coming from Mars and Vesta. Here we explore the possibility that the silicate Earth and impactor were compositionally distinct with respect to oxygen isotopes, and that the terrestrial magma ocean and lunar-forming material underwent turbulent mixing and equilibration in the energetic aftermath of the gia…
We compare the number of lunar craters larger than 15 km across and younger than 1.1 Ga to the estimates of the number of craters that could have been formed for 1.1 Ga if the number of near-Earth objects and their orbital elements during that time were close to the corresponding current values. The comparison was performed for craters over the entire lunar surface and in the region of the Oceanus Procellarum and maria on the near side of the Moon. In these estimates, we used the values of collision probabilities of near-Earth objects with the Moon and the dependences of the crater diameters o…
In the giant impact hypothesis for lunar origin, the Moon accreted from an equatorial circum-terrestrial disk; however the current lunar orbital inclination of 5 degrees requires a subsequent dynamical process that is still debated. In addition, the giant impact theory has been challenged by the Moon's unexpectedly Earth-like isotopic composition. Here, we show that tidal dissipation due to lunar obliquity was an important effect during the Moon's tidal evolution, and the past lunar inclination must have been very large, defying theoretical explanations. We present a new tidal evolution model …
We analyze lunar impact flashes recorded by our team during runs in December 2007, 2011, 2013 and 2014. In total, 12 impact flashes with magnitudes ranging between 7.1 and 9.3 in V band were identified. From these, 9 events could be linked to the Geminid stream. Using these observations the ratio of luminous energy emitted in the flashes with respect to the kinetic energy of the impactors for meteoroids of the Geminid stream is estimated. By making use of the known Geminids meteoroid flux on Earth we found this ratio to be 2.1x10$^{-3}$ on average. We compare this luminous efficiency with othe…
We report the results of detailed investigation of the Earth's transmission spectra during the lunar eclipse on UT 2011 December 10. The spectra were taken by using the High Dispersion Spectrograph (HDS) mounted on the Subaru 8.2 m telescope with unprecedented resolutions both in time and wavelength (300 s exposure time in umbra and 160,000 spectral resolution, respectively). In our penumbra and umbra data, we detected the individual absorption lines of O2 and H2O in transmission spectra and found that it became deeper as the eclipse became deeper. It indicates that the sunlight reaching the M…
There is a growing interest in Lunar exploration fed by the perception that the Moon can be made accessible to low-cost missions in the next decade. The on-going projects to set a communications relay in Lunar orbit and a deep space Gateway, as well as the spreading of commercial-of-the shelf (COTS) technology for small space platforms such as the cubesats contribute to this perception. Small, cubesat size satellites orbiting the Moon offer ample opportunities to study the Moon and enjoy an advantage point to monitor the Solar System and the large scale interaction between the Earth and the so…
We formulate the lunar cratering distribution and verify the cratering asymmetries generated by the main-belt asteroids (MBAs) as well as the near-Earth objects (NEOs). Based on a planar model that excludes the terrestrial and lunar gravitations on the impactors and assuming the impactor encounter speed with Earth $v_{\rm{enc}}$ is higher than the lunar orbital speed $v_{\rm{M}}$, we rigorously integrated the lunar cratering distribution, and derived its approximation to the first order of $v_{\rm{M}}/v_{\rm{enc}}$. Numerical simulations of lunar bombardment by the MBAs during the late heavy b…
A co-orbital asteroid shares the orbit of a secondary body about its primary. Though more commonly encountered as an asteroid that shares a planet's orbit around the Sun, a co-orbital asteroid could similarly share the orbit of the Moon around the Earth. Though such asteroids would be close to Earth and so relatively bright, their rapid on-sky motion is such that they might escape detection by near-Earth asteroid surveys. The discovery of such lunar co-orbital asteroids (which we will refer to generically here as Lunar Trojans or LTs) would advance our understanding of inner Solar System orbit…
Observation Timelines for the Potential Lunar Impact of Asteroid 2024 YR4
Tsinghua University（清华大学）；University of California, Santa Cruz（加州大学圣克鲁兹分校）；National Astronomical Observatory of Japan（日本国立天文台）；Nanjing University（南京大学）；Inner Mongolia University of Technology（内蒙古工业大学）
Overabundances in highly siderophile elements (HSEs) of Earth's mantle can be explained by conveyance from a singular, immense (3000 km in a diameter) "Late Veneer" impactor of chondritic composition, subsequent to lunar formation and terrestrial core-closure. Such rocky objects of approximately lunar mass (about 0.01 M_E) ought to be differentiated, such that nearly all of their HSE payload is sequestered into iron cores. Here, we analyze the mechanical and chemical fate of the core of such a Late Veneer impactor, and trace how its HSEs are suspended - and thus pollute - the mantle. For the s…
There is growing interest in the possibility that the resource base of the Solar System might in future be used to supplement the economic resources of our own planet. As the Earth's closest celestial neighbour, the Moon is sure to feature prominently in these developments. In this paper I review what is currently known about economically exploitable resources on the Moon, while also stressing the need for continued lunar exploration. I find that, although it is difficult to identify any single lunar resource that will be sufficiently valuable to drive a lunar resource extraction industry on i…
Aims. An asymmetric dust cloud was detected around the Moon by the Lunar Dust Experiment on board the Lunar Atmosphere and Dust Environment Explorer mission. We investigate the dynamics of the grains that escape the Moon and their configuration in the Earth-Moon system. Methods. We use a plausible initial ejecta distribution and mass production rate for the ejected dust. Various forces, including the solar radiation pressure and the gravity of the Moon, Earth, and Sun, are considered in the dynamical model, and direct numerical integrations of trajectories of dust particles are performed. The …
Accurate estimation of cratering asymmetry on the Moon is crucial for understanding Moon evolution history. Early studies of cratering asymmetry have omitted the contributions of high lunar obliquity and inclination. Here, we include lunar obliquity and inclination as new controlling variables to derive the cratering rate spatial variation as a function of longitude and latitude. With examining the influence of lunar obliquity and inclination on the asteroids population encountered by the Moon, we then have derived general formulas of the cratering rate spatial variation based on the crater sc…
The detections of small, rocky exoplanets have surged in recent years and will likely continue to do so. To know whether a rocky exoplanet is habitable, we have to characterise its atmosphere and surface. A promising characterisation method for rocky exoplanets is direct detection using spectropolarimetry. This method will be based on single pixel signals, because spatially resolving exoplanets is impossible with current and near-future instruments. Well-tested retrieval algorithms are essential to interpret these single pixel signals in terms of atmospheric composition, cloud and surface cove…
An important goal within the quest for detecting an Earth-like extrasolar planet, will be to identify atmospheric gaseous bio-signatures. Observations of the light transmitted through the Earth's atmosphere, as for an extrasolar planet, will be the first step for future comparisons. We have completed observations of the Earth during a Lunar eclipse, a unique situation similar to that of a transiting planet. We aim at showing what species could be detected in its atmosphere at optical wavelengths, where a lot of photons are available in the masked stellar light. We present observations of the 2…
An ancient Venusian rock could constrain that planet's history, and reveal the past existence of oceans. Such samples may persist on the Moon, which lacks an atmosphere and significant geological activity. We demonstrate that if Venus' atmosphere was at any point thin and similar to Earth's, then asteroid impacts transferred potentially detectable amounts of Venusian surface material to the Lunar regolith. Venus experiences an enhanced flux relative to Earth of asteroid collisions that eject lightly-shocked ($\lesssim 40$ GPa) surface material. Initial launch conditions plus close-encounters a…
The importance of highly siderophile elements (HSEs) to track planetary late accretion has long been recognized. However, the precise nature of the Moon's accretional history remains enigmatic. There exists a significant mismatch of HSE budgets between the Earth and Moon, with the Earth disproportionally accreted far more HSEs than the Moon did. Several scenarios have been proposed to explain this conundrum, including the delivery of HSEs to Earth by a few big impactors, the accretion of pebble-sized objects on dynamically cold orbits that enhanced the Earth's gravitational focusing factor, an…
Given the renewed scientific interest in lunar exploration missions, complete understanding of lunar near surface environment and its exosphere under different conditions is of paramount importance. Lunar exosphere has been extensively studied by ground based observations [18,19,20,21,22,23] and hypothesized by different models[1,2,3,4,5,6,7,8,9,10,11,12,13]. In present work, we have discussed overlooked possible sources behind changes in the lunar exosphere when the Moon passes through the penumbra and umbra of the Earth during a lunar eclipse. The dusty turbulent environment due to planetary…
There exist cislunar and trans-lunar libration points near the Moon, which are referred as the LL1 and LL2 points respectively and can generate the different types of low-energy trajectories transferring from Earth to Moon. The time-dependent analytic model including the gravitational forces from the Sun, Earth and Moon is employed to investigate the energy-minimal and practical transfer trajectories. However, different from the circular restricted three-body problem, the equivalent gravitational equilibria are defined according to the geometry of instantaneous Hill's boundary due to the gravi…
A model based on celestial geometry and atmospheric physics predicts the dimming and the color of lunar eclipses. Corresponding visual magnitudes and color indices for eclipses from year 2000 through 2050 are listed. The enlargement of the Earth's umbral shadow reported by observers for over 300 years is explained. The geometrical aspects of the model are the sizes and separations of the Sun, Moon and Earth. Atmospheric effects include refraction, absorption and focusing of sunlight.
Physical characterization of Earth's quasi-satellite 2025 PN7
Finnish Centre for Astronomy with ESO, University of Turku（芬兰天文台（ESO合作中心））；University of Helsinki（赫尔辛基大学）；Asteroid Engineering Laboratory, Luleå University of Technology（鲁勒厄理工大学小行星工程实验室）；Instituto de Astrofísica de Canarias（加那利群岛天体物理研究所）；Universidad de La Laguna（拉古纳大学）
Of the 342 planets discovered so far orbiting other stars, 58 "transit" the stellar disk, meaning that they can be detected by a periodic decrease in the starlight flux. The light from the star passes through the atmosphere of the planet, and in a few cases the basic atmospheric composition of the planet can be estimated. As we get closer to finding analogues of Earth, an important consideration toward the characterization of exoplanetary atmospheres is what the transmission spectrum of our planet looks like. Here we report the optical and near-infrared transmission spectrum of the Earth, obta…
Embryos of the Moon and the Earth may have formed as a result of contraction of a common parental rarefied condensation. The required angular momentum of this condensation could largely be acquired in a collision of two rarefied condensations producing the parental condensation. With the subsequent growth of embryos of the Moon and the Earth taken into account, the total mass of as-formed embryos needed to reach the current angular momentum of the Earth-Moon system could be below 0.01 of the Earth mass. For the low lunar iron abundance to be reproduced with the growth of originally iron-deplet…
The Radiation Monitor (RADOM) payload is a miniature dosimeter-spectrometer onboard Chandrayaan-1 mission for monitoring the local radiation environment in near-Earth space and in lunar space. RADOM measured the total absorbed dose and spectrum of the deposited energy from high energy particles in near-Earth space, en-route and in lunar orbit. RADOM was the first experiment to be switched on soon after the launch of Chandrayaan-1 and was operational till the end of the mission. This paper summarizes the observations carried out by RADOM during the entire life time of the Chandrayaan-1 mission …
