On the possible presence of ice on the Moon

Watson, K.; Murray, Bruce C.; Brown, Harrison

doi:10.1029/jz066i005p01598

Cited by 189 publications

(88 citation statements)

References 4 publications

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“…The identification of different minerals provides clues to the processes that formed or altered these solar system bodies. On the Moon, regolith particles of diameters ≤25 μm dominate the remotely-sensed spectral properties of the surface over the visible/near-infrared wavelength region (Pieters et al, 1993a).Water ice has long been postulated to exist in permanently shaded areas at the lunar poles (c.f., Watson et al, 1961;Arnold, 1979). Recent observations provide conflicting evidence for the presence and form of lunar polar water ice.…”

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confidence: 99%

A newly-identified spectral reflectance signature near the lunar South pole and the South Pole-Aitken Basin

et al. 2008

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Signal analysis of Galileo images of the Moon suggests the presence of an absorption band centered near 0.7 μm in the reflectance spectra of areas located adjacent to the equatorward walls of lunar craters at latitudes ranging from −58 to −78• , and areas contained in the South Pole-Aitken Basin. We propose three potential explanations: an Fe 2+ →Fe 3+ charge transfer transition in oxidized iron in clinopyroxenes (high-Ca bearing pyroxenes) or phyllosilicates (Fe-and Mg-bearing sheet silicates containing adsorbed H 2 O and interlayer OH − ), or an effect of titanium in ilmenite (a common lunar opaque material). No identification of the mineralogy is conclusive. The presence and nature of the absorption feature could be confirmed using AMICA images of the lunar far side from the Japanese mission Hayabusa, spectroscopic results from the Japanese mission Selene scheduled for launch in 2007, or the Moon Mineralology Mapper on the Indian mission Chandrayaan-1. Key words: Moon, lunar surface composition, spectral reflectance, lunar mineralogy, lunar remote sensing. Motivation and Background for Search for Lunar PhyllosilicatesSpectral observations of reflected sunlight from the surface of a planetary regolith serve as a remote sensing probe of surface mineralogical composition and particle state. Variations from the solar spectrum in the spectrum of a planetary regolith, apparent in the form of broad absorption features, reflect the presence of electronic charge transfers and vibrations between ions governed by structural spacing within crystals of a specific mineralogy (c.f., Burns, 1993). By identifying and analyzing these spectral variations, the underlying mineralogy of the planetary regolith can be determined. The identification of different minerals provides clues to the processes that formed or altered these solar system bodies. On the Moon, regolith particles of diameters ≤25 μm dominate the remotely-sensed spectral properties of the surface over the visible/near-infrared wavelength region (Pieters et al., 1993a).Water ice has long been postulated to exist in permanently shaded areas at the lunar poles (c.f., Watson et al., 1961;Arnold, 1979). Recent observations provide conflicting evidence for the presence and form of lunar polar water ice. Clementine bistatic radar detected a weak sig- * Present address: MMT Observatory, P.O. Box 210065, University of Arizona, Tucson, Arizona 85721. nal at the lunar South pole attributed to water ice (Nozette et al., 1996), while Lunar Prospector has recently detected large amounts of H at both poles (Feldman et al., 2000(Feldman et al., , 2001. Conversely, ground-based radar searches show no bright signal suggesting water ice at either pole (Stacy et al., 1997), andCampbell et al. (2006) find no evidence of thick deposits of ice at the South pole. Reanalysis of the Clementine radar data by Simpson and Tyler (1999) suggest that the radar reflection results were caused by underlying variations in terrain. Galileo near-infrared spectra detected no sign of the prominent 3.0-μm...

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A newly-identified spectral reflectance signature near the lunar South pole and the South Pole-Aitken Basin

et al. 2008

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“…[2] The existence of ice in the polar cold traps of the Moon has been postulated for many years [e.g., Watson et al, 1961;Arnold, 1979] because of a combination of the Moon's small obliquity (~1.5°) and the large variation in topographic relief near the poles. These two factors result in large areas (more than 30,000 km 2 at both poles) [McGovern et al, 2013] that remain in permanent darkness and are thus very cold [Vasavada et al, 1999;Paige et al, 2010b].…”

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Evidence for water ice on the Moon: Results for anomalous polar craters from the LRO Mini‐RF imaging radar

et al. 2013

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[1] The Mini-RF radar instrument on the Lunar Reconnaissance Orbiter spacecraft mapped both lunar poles in two different RF wavelengths (complete mapping at 12.6 cm S-band and partial mapping at 4.2 cm X-band) in two look directions, removing much of the ambiguity of previous Earth-and spacecraft-based radar mapping of the Moon's polar regions. The poles are typical highland terrain, showing expected values of radar cross section (albedo) and circular polarization ratio (CPR). Most fresh craters display high values of CPR in and outside the crater rim; the pattern of these CPR distributions is consistent with high levels of wavelength-scale surface roughness associated with the presence of block fields, impact melt flows, and fallback breccia. A different class of polar crater exhibits high CPR only in their interiors, interiors that are both permanently dark and very cold (less than 100 K). Application of scattering models developed previously suggests that these anomalously high-CPR deposits exhibit behavior consistent with the presence of water ice. If this interpretation is correct, then both poles may contain several hundred million tons of water in the form of relatively "clean" ice, all within the upper couple of meters of the lunar surface. The existence of significant water ice deposits enables both long-term human habitation of the Moon and the creation of a permanent cislunar space transportation system based upon the harvest and use of lunar propellant.

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“…Arnold (1979) investigated ice survivability on the Moon, following up the work of Watson et al (1961). Arnold proposed that solar wind reduction of iron in the lunar regolith, such as is now implicated in space weathering (Noble et al, 2001), could create significant amounts of water, which could then potentially make its way to cold traps in permanently shadowed craters near the lunar poles.…”

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Astronomical Observations of Volatiles on Asteroids

Rivkin¹,

Campins²,

Emery³

et al. 2015

Asteroids IV

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We have long known that water and hydroxyl are important components in meteorites and asteroids. However, in the time since the publication of Asteroids III, evolution of astronomical instrumentation, laboratory capabilities, and theoretical models have led to great advances in our understanding of H 2 O/OH on small bodies, and spacecraft observations of the Moon and Vesta have important implications for our interpretations of the asteroidal population. We begin this chapter with the importance of water/OH in asteroids, after which we will discuss their spectral features throughout the visible and near-infrared. We continue with an overview of the findings in meteorites and asteroids, closing with a discussion of future opportunities, the results from which we can anticipate finding in Asteroids V. Because this topic is of broad importance to asteroids, we also point to relevant in-depth discussions elsewhere in this volume.1 Water ice sublimation and processes that create, incorporate, or deliver volatiles to the asteroid belt Accretion/Solar system formation 1.1The concept of the "snow line" (also known as "water-frost line") is often used in discussing the water inventory of small bodies in our solar system. The snow line is the heliocentric distance at which water ice is stable enough to be accreted into planetesimals. The placement of the snow line has varied in different models. A location just inside Jupiter helps explain the greater mass of the giant planets as they accrete a larger fraction of the mass in the solar nebula. Although the location of the snow line before and during planet formation is uncertain, some studies show it may have fallen within the asteroid belt (Lunine, 2006). The location of the snow line in our solar system coinciding with the asteroid belt is consistent with observations of disks around other stars (e.g., Su et al., 2013), where planetesimal rings tend to coincide with the snow line around those stars. However, it seems the relatively simple concept of a static snow line requires revisions in light of new results on several fronts. For instance, the snow line likely moved with time as the Sun's luminosity changed early in solar system history (e.g., Martin and Livio, 2012). Even though there is no agreement on the details of planetesimal formation and growth, some models favor the growth of ~100 km-scale planetesimals directly from cm-scale pieces Cuzzi et al., 2010; for a dissenting view see Weidenschilling, 2011). Hence, the timing of those assemblies as conditions change could have a strong influence on the amount of radioactive elements present in a planetesimal's interior and on its rock-to-ice ratio, further complicating the concept of a snow line. Recent observations also point to a more complex picture. For example, the concept of an asteroid-comet continuum, where there is no clear boundary between primitive asteroids and cometary nuclei (e.g., Gounelle, 2011) is gaining support and is consistent with the intermittent cometary behavior of some main belt and near-E...

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On the possible presence of ice on the Moon

Cited by 189 publications

References 4 publications

A newly-identified spectral reflectance signature near the lunar South pole and the South Pole-Aitken Basin

A newly-identified spectral reflectance signature near the lunar South pole and the South Pole-Aitken Basin

Evidence for water ice on the Moon: Results for anomalous polar craters from the LRO Mini‐RF imaging radar

Astronomical Observations of Volatiles on Asteroids

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