Surface Water at Lunar Magnetic Anomalies

Li, Shuai; Garrick‐Bethell, I.

doi:10.1029/2019gl084890

Cited by 23 publications

(15 citation statements)

References 44 publications

(95 reference statements)

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“…Similar to previous studies (e.g., Li and Garrick-Bethell 2019), recent results by Hess et al (2020) indicate a weaker 3-µm band at the swirl locations than on the surrounding surface. This finding supports the assumption that the magnetic field locally reduces the flux of solar wind protons, leading to a reduced rate of OH/H 2 O formation in the regolith.…”

Section: Local Anomaliessupporting

confidence: 90%

Water Group Exospheres and Surface Interactions on the Moon, Mercury, and Ceres

et al. 2021

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Water ice, abundant in the outer solar system, is volatile in the inner solar system. On the largest airless bodies of the inner solar system (Mercury, the Moon, Ceres), water can be an exospheric species but also occurs in its condensed form. Mercury hosts water ice deposits in permanently shadowed regions near its poles that act as cold traps. Water ice is also present on the Moon, where these polar deposits are of great interest in the context of future lunar exploration. The lunar surface releases either OH or H2O during meteoroid showers, and both of these species are generated by reaction of implanted solar wind protons with metal oxides in the regolith. A consequence of the ongoing interaction between the solar wind and the surface is a surficial hydroxyl population that has been observed on the Moon. Dwarf planet Ceres has enough gravity to have a gravitationally-bound water exosphere, and also has permanently shadowed regions near its poles, with bright ice deposits found in the most long-lived of its cold traps. Tantalizing evidence for cold trapped water ice and exospheres of molecular water has emerged, but even basic questions remain open. The relative and absolute magnitudes of sources of water on Mercury and the Moon remain largely unknown. Exospheres can transport water to cold traps, but the efficiency of this process remains uncertain. Here, the status of observations, theory, and laboratory measurements is reviewed.

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Section: Local Anomaliessupporting

confidence: 90%

Water Group Exospheres and Surface Interactions on the Moon, Mercury, and Ceres

et al. 2021

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“…Here, only the radial component is used in Parker's Method. equatorial dipole would channel solar wind hydrogen over a substantial fraction of the surface as the Moon spins, in contrast to a spin-aligned dipole, which would block solar wind access from most of the Moon. If the Moon's polar hydrogen deposits are related to a global-scale "water cycle" related to solar wind hydroxylation of the entire lunar surface (Li and Garrick-Bethell, 2019;Li & Milliken, 2017;Pieters et al, 2009), then a near-equatorial dipole could have facilitated their accumulation.…”

Section: Evidence For Near-equatorial Lunar Paleopoles and A Nonaxialmentioning

confidence: 99%

Evidence for an Ancient Near‐Equatorial Lunar Dipole From Higher Precision Inversions of Crustal Magnetization

Maxwell

Garrick‐Bethell

2020

JGR Planets

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Studies of lunar paleopoles have been used to make a variety of inferences about past episodes of true polar wander and the orientation of the ancient dynamo field. However, the large and variable uncertainties commonly reported for such studies make robust conclusions difficult. To make further progress, we used synthetic magnetic anomalies to assess a common method to estimate magnetization direction uncertainty. We find that with this method, magnetic anomalies with higher inclinations have systematically higher uncertainties than lower inclination anomalies. We call this effect inclination bias. A similar effect is found for declination, but it is weaker. We also find that this method often produces overly conservative uncertainty estimates. To avoid these effects, we use Monte Carlo methods to determine magnetization direction uncertainty. We apply our methods to five lunar magnetic anomalies with a wide range of reported magnetization directions and paleopole locations. We find that inclination bias partly explains the previously reported anomalously high and low direction uncertainties for two of these anomalies: Reiner Gamma and Airy. Our more robust uncertainties allow us to conclude that four paleopoles are located near the equator. Such low latitudes cannot be explained by true polar wander inferred from other independent datasets, such as the lunar gravity field and the polar hydrogen distribution. This in turn implies that the dynamo axis was once offset from the spin axis.

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“…of the brightest terrain on the lunar maria. Finally, it is important to note that Reiner Gamma is not strongly correlated with surface water; several other swirls show much stronger correlations (Li & Garrick-Bethell, 2019). These other swirls, such as Airy (Fig.…”

Section: Methodsmentioning

confidence: 91%

“…Together, these measurements will elucidate how the Moon and bodies like it have become magnetized. (Li & Garrick-Bethell, 2019).…”

mentioning

confidence: 99%

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NanoSWARM: NanoSatellites for Space Weathering, Surface Water, Solar Wind, and Remanent Magnetism

Garrick‐Bethell

Paige

Burton³

et al. 2021

Bulletin of the AAS

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The NanoSWARM mission concept is a detailed investigation of particles and magnetic fields to help characterize the surfaces of airless planetary bodies, their volatile element distributions, and their geophysical histories. NanoSWARM investigates unique regions in the solar system where these processes come together: lunar swirls.NanoSWARM would be the first demonstration of a planetary-class carrier vehicle equipped with dozens of nanosatellites, each capable of performing measurements either too risky or difficult for the carrier. This architecture greatly facilitates contributed nanosatellites and complete sub-missions from other nations, students, or participating scientists. NanoSWARM was proposed to theDiscovery program in 2019. It was one of 6 missions that received the highest possible ranking of Category 1, but it did not move forward to Phase A. The commercial space flight community is well on its way toward mass production of small spacecraft. An openness within the planetary community toward building dozens of instruments or spacecraft could open up entirely new regimes of measurement in space.1. Science overview: NanoSWARM (NanoSatellites for Space Weathering, Surface Water, Solar Wind, And Remanent Magnetism) uses a new type of space mission architecture to address four complementary science goals, becoming, in effect, four missions in one. NanoSWARM launches 19 NanoSatellites (plus spares) to fly just above the surface at five target sites spread across the Moon's near and far sides. This architecture permits a science investigation of substantial breadth and depth, beyond what could be accomplished with a single orbiter, rover, or lander.NanoSWARM's first goal is to elucidate the mechanisms of space weathering -the alteration of an airless body's optical properties due to solar wind and micrometeoroid bombardment. This ubiquitous process affects spectral data from 0.1-10 microns and, thereby, our ability to determine the compositions of bodies ranging from Mercury to asteroids. Despite decades of study, we do not have a complete model for how space weathering operates. In particular, the relative contributions from micrometeoroids and solar wind flux and the influence of local soil mineralogy on the optical effects are not completely understood. To address this problem, NanoSWARM investigates unique locations on the Moon where solar wind flux is modified while the micrometeoroid flux and mineralogy remain constant: lunar swirls (Fig. 1). The M 3 instrument on Chandrayaan-1 as well as Diviner and LAMP on Lunar Reconnaissance Orbiter (LRO) quantified the spectral variations across these features. By performing the first spatially resolved near-surface solar wind flux measurements across multiple swirls with different soil iron contents, NanoSWARM quantitatively resolves how the solar wind affects the optical properties of the Moon and similar silicate bodies.NanoSWARM's second goal is to constrain how near-surface water forms and is distributed on airless bodies like the Moon, Mercury, and asteroid...

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Surface Water at Lunar Magnetic Anomalies

Cited by 23 publications

References 44 publications

Water Group Exospheres and Surface Interactions on the Moon, Mercury, and Ceres

Water Group Exospheres and Surface Interactions on the Moon, Mercury, and Ceres

Evidence for an Ancient Near‐Equatorial Lunar Dipole From Higher Precision Inversions of Crustal Magnetization

NanoSWARM: NanoSatellites for Space Weathering, Surface Water, Solar Wind, and Remanent Magnetism

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