Lunar red spots: Possible pre-mare materials

doi:10.1016/0012-821X(74)90170-8

Earth and Planetary Science Letters

Volume 21, Issue 4, March 1974, Pages 331-341

https://doi.org/10.1016/0012-821X(74)90170-8 Get rights and content

Abstract

Some anomalous red features observed on the moon by Whitaker are examined in detail. Crater counts and regional stratigraphy suggest that ages for these features are comparable to that of lunar highland material. Initial gamma-ray spectrometry indicates higher than average native radioactivity is associated with certain red areas. A possible explanation for these observations is that the red objects are the surface manifestation of highly radioactive pre-mare basalts (Apollo 14/KREEP/norite material). Conclusive proof of the nature of these objects will depend on the study of returned samples, making them ideal candidates for future space missions, especially for unmanned vehicles such as the Soviet Union's Luna 20.

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Cited by (41)

Geology of Mairan middle dome: Its implication to silicic volcanism on the Moon
2018, Planetary and Space Science
Citation Excerpt :
The focus of this study is MMD, the largest of four small domes (Fig. 2). Mairan middle dome is a lunar “red spot” characterized by relatively high albedo, strong absorption in the UV, and is thought to be a volcanic construct produced by non-mare volcanism connected with KREEP basalts or even more evolved highlands composition, such as dacite or rhyolite (Malin, 1974; Wood and Head, 1975; Head and McCord, 1978). These volcanic centers appear to be petrologic anomalies on the Moon that represent strong geochemical departures from primordial compositions, and are indicators of magma processing.
Mairan middle dome (MMD), a lunar “red spot” of silicic composition, and the surrounding maria were emplaced in the same two major episodes of volcanism. Both episodes at MMD included eruptions of low-FeO, silica-rich lava, while basaltic lava flooded the surrounding terrain during these episodes. MMD is a composite of, at least, seven small volcanic edifices. Crater counts suggest that the first episode occurred at ∼3.75 ± 0.1 Ga when low FeO, high-silica lavas erupted at MMD, and Mairan T, the small dome 11 km northwest of MMD. At about the same time, basaltic composition lava erupted southeast of MMD. A second major episode of volcanism at MMD occurred at ∼3.35 ± 0.2 Ga when low FeO, and high-silica lavas erupted at the summits of individual small volcanic edifices and a central plateau area between them. During this phase, mare basaltic lavas again flooded the area surrounding MMD and Mairan T. This sequence of events indicates that the emplacement of MMD is more complex than previously thought. In addition, the simultaneous eruption of basaltic composition lavas and low FeO, high-SiO₂ lavas in this region supports the underplating model for production of magma to form the “red spots” volcanic complexes on the Moon.
Hansteen Mons: An LROC geological perspective
2017, Icarus
Mons Hansteen is a relatively high-albedo, well-known lunar ``red spot'' located on the southern margin of Oceanus Procellarum (2.3°S, 50.2°W). It is an arrowhead-shaped (∼ 25 km on a side), two-layer mesa with a small cone-shaped massif on its north edge formed by three morphologically and compositionally distinct geologic units. These units were emplaced in three phases over nearly 200 million years. The oldest (∼3.74 Ga), Hilly–Dissected unit, composed of high-silica, and low-FeO content materials formed a low, steep sided mesa. The materials of this unit erupted mainly from vents along northeast- and northwest-trending sets of fractures. The Pitted unit, which comprises the upper-tier mesa, is composed of high-silica and even lower-FeO content materials. This material was erupted at ∼ 3.5 Ga from numerous closely spaced vents (i.e., pits) formed along closely spaced northeast-southwest-trending sets of fractures. At nearly the same time, eruptions of lower silica and higher FeO materials occurred on the north flank of Mons Hansteen at the intersection of two major fractures to produce the North Massif unit. The eruptions that created the North Massif units also produced materials that thinly blanketed small areas of the Hilly-Dissected and Pitted units on the north flank of Mons Hansteen. Also at nearly the same time (i.e., ∼ 3.5 Ga), basalt flows formed the surrounding mare. Each unit of Mons Hansteen appears to be mantled by locally derived ash, which only modestly contaminated the other units. The morphology of Mons Hansteen (especially the Pitted unit) suggests a style of volcanism where only a relatively small amount of material is explosively erupted from numerous, closely spaced vents.
The distribution and origin of lunar light plains around Orientale basin
2016, Icarus
Lunar light plains are relatively flat, smooth to gently rolling deposits that occur in crater floors and other topographic lows in the lunar highlands, with albedo values comparable to surrounding highland terrain. Once interpreted to be the product of highland volcanism, Apollo 16 samples from the light plains of the Cayley Formation led to the interpretation that most light plains form from the deposition of fluidized basin ejecta. Conflicting relative age estimates suggest that light plains are ejecta from the Orientale and Imbrium basins, or from a larger number of impact events combined with possible volcanic eruptions. Here we examine the distribution, variability, and origin of light plains associated with the Orientale basin using data from the Lunar Reconnaissance Orbiter Camera (LROC). We find that the distribution, composition, and age of the light plains to the north and northwest of the Orientale basin are consistent with an origin with the formation of Orientale. In this case, the Orientale basin-forming impact significantly altered the surface within four basin radii from the rim.
The Lassell massif-A silicic lunar volcano
2016, Icarus
Citation Excerpt :
Nevertheless, both telescopic and orbital observations of morphologically and compositionally distinct constructs, including the nearside lunar red spots (regions of strong ultraviolet (UV) absorption), have supported non-mare, Si-rich volcanic interpretations (e.g., Whitaker, 1972a; Malin, 1974; Wood and Head, 1975; Head and McCord, 1978; Müller et al., 1986; Chevrel et al., 1999; Hawke et al., 2001, 2003; Hagerty et al., 2006; Glotch et al., 2010; Wagner et al., 2010; Glotch et al., 2011; Jolliff et al., 2011; Kusuma et al., 2012; Lawrence et al., 2014; Wilson et al., 2015). The lunar red spots (first identified based on a spectral contrast between the UV and visible) include Hansteen Alpha, Herigonius ε and π, the Gruithuisen domes, Montes Riphaeus, portions of Aristarchus crater and its plateau, and the Lassell massif (Whitaker, 1972b; Malin, 1974; Wood and Head, 1975; Bruno et al., 1991; Hawke et al., 2001). Many red spots, including the Lassell massif, correlate with anomalously high Th signatures in Lunar Prospector Gamma-Ray Spectrometer (LP GRS) data, consistent with evolved magma sources (Hawke et al., 2001; Lawrence et al., 2003; Hagerty et al., 2006).
Lunar surface volcanic processes are dominated by mare-producing basaltic extrusions. However, spectral anomalies, landform morphology, and granitic or rhyolitic components found in the Apollo sample suites indicate limited occurrences of non-mare, geochemically evolved (Si-enriched) volcanic deposits. Recent thermal infrared spectroscopy, high-resolution imagery, and topographic data from the Lunar Reconnaissance Orbiter (LRO) show that most of the historic “red spots” and other, less well-known locations on the Moon, are indeed silica rich (relative to basalt). Here we present a geologic investigation of the Lassell massif (14.65°S, 350.96°E) near the center of Alphonsus A basin in Mare Nubium, where high-silica thermal emission signals correspond with morphological indications of viscous (possibly also explosive) extrusion, and small-scale, low-reflectance deposits occur in a variety of stratigraphic relationships. Multiple layers with stair-step lobate forms suggest different eruption events or pulsing within a single eruption. Absolute model ages derived from crater size-frequency distributions (CSFDs) indicate that the northern parts of the massif were emplaced at ∼4 Ga, before the surrounding mare. However, CSFDs also indicate the possibility of more recent resurfacing events. The complex resurfacing history might be explained by either continuous resurfacing due to mass wasting and/or the emplacement of pyroclastics. Relatively low-reflectance deposits are visible at meter-scale resolutions (below detection limits for compositional analysis) at multiple locations across the massif, suggestive of pyroclastic activity, a quenched flow surface, or late-stage mafic materials. Compositional evidence from 7-band UV/VIS spectral data at the kilometer-scale and morphologic evidence for possible caldera collapse and/or explosive venting support the interpretation of a complex volcanic history for the Lassell massif.
The lunar Gruithuisen silicic extrusive domes: Topographic configuration, morphology, ages, and internal structure
2016, Icarus
Citation Excerpt :
Both types of flows occur at different elevations indicating that their sources exist at different levels within the Gruithuisen-Gamma dome. The Gruithuisen domes form three unusually high (1.4–1.7 km) topographic features that are associated with one of the lunar red spot complexes (Whitaker, 1972; Malin, 1974). The general shape of the domes and their specific spectral characteristics have been interpreted as evidence of formation by eruptions of high-viscosity, silica-rich lavas (Wood and Head, 1975; Head et al., 1978; Head and McCord, 1978; Wilson and Head, 2003).
The Gruithuisen domes, situated on the western portion of the Imbrium basin rim, form three tall mountains (NW, Gamma, Delta) totaling ∼780 km³ in volume. The shapes of the domes are significantly different from that of mare-type domes elsewhere on the Moon. We use data from the Lunar Reconnaissance Orbiter (LRO) and Kaguya missions (LRO Lunar Orbiter Laser Altimeter, Lunar Reconnaissance Orbiter Camera, Diviner, and the Kaguya imager) to characterize the domes and assess models for their origin. The configuration of the domes (steep slopes, up to ∼18–20°) and their specific remote sensing characteristics (strong downturn in the UV, and results from the M3 and Diviner instruments) suggest that the domes formed by eruptions of highly viscous lava. The estimated surface volumes of the domes vary from ∼20 km³ (NW dome) to ∼290 km³ (Gamma dome) to ∼470 km³ (Delta dome). The domes occur on the portion of the Imbrium basin rim that is overlain by ejecta from the post-Imbrium Iridum crater. In some areas, relatively high albedo smooth volcanic plains are seen within the Iridum ejecta near the Gruithuisen domes, and low albedo mare deposits surround and embay the domes and Iridum crater. Dating of different units and features by crater counts indicates that impact melts from the Iridum basin are ∼3.9 Ga old, the domes Gamma and Delta are ∼3.8 Ga, and the ages of the plains near the domes vary from ∼2.3 to ∼3.6 Ga. A fresh impact crater exposes the internal structure of the Gamma dome. The most prominent features on the wall of the crater are rough, blocky layers that are typical of volcanic plains in the highlands and maria around the domes. The layers are interleaved with fine-grained materials of higher and lower albedo and the visible orientation of the layers changes over short (a few hundred meters) distances. These characteristics of the internal structure of the dome are consistent with eruptions of high viscosity lava (rough layers) that alternated with possible explosive activity (fine-grained materials). The spatial association of the Gruithuisen domes with the highland lava plains resembles the situation in which bimodal volcanism occur on Earth. The terrestrial association can be due to either fractional crystallization in basaltic magma reservoirs or remelting of high-silica crustal materials. In the first case, the evolved melts appear in later stages of volcanic activity and in the second case these melts are formed near the beginning of evolution of the magmatic systems. The age estimates of the Gruithuisen domes and the surrounding volcanic plains are more consistent with the crustal remelting scenario. However, remelting of primary anorthositic crust cannot readily produce the silica-rich melts and requires the presence of pre-existing granite-like materials. Formation of the domes by fractional crystallization avoids this difficulty but requires explanation of the older age of the domes relative to the volcanic plains in the surroundings. A third option is that the domes are unrelated genetically to the mare deposits.
Comparison of lunar red spots including the crater copernicus
2016, Icarus
The lunar red spots, Helmet, Hansteen Alpha, and the NW quadrant of the crater Copernicus, were selected for a complex comparative investigation of their characteristics measured by the spacecraft Clementine, LRO, and Chandrayaan-1. For the analysis we used the following parameters: the reflectance A(750 nm), color-ratio A(750 nm)/A(415 nm), parameter of optical micro-roughness (LRO WAC), parameters deduced from LRO Diviner data, optical maturity OMAT, abundance of FeO and TiO₂ (Clementine UVVIS and LRO WAC data), oxygen content determined using Lunar Prospector data, and parameters characterizing the 0.95-µm and 2.2-µm bands of Fe²⁺ ions (crystal field bands), and 2.8-µm band of H₂O/OH and/or Fe²⁺ ions. The red spots Helmet and Hansteen Alpha are considered to be extrusions of rhyolite composition, which can be attributed to the Nectarian period; we did not find contradictions of this assumption. As for the Copernicus red spot, this, perhaps, is a similar formation that has been destroyed by the impact. We demonstrate that the material of the Copernicus red spot probably has the same composition as the classical red spots Helmet and Hansteen Alpha. The distributions of the parameter of optical micro-roughness and optical maturity OMAT show that the Copernicus red anomaly was not formed during the long evolution of the lunar surface, but results from crater formation. We find several confirmations of the hypothesis that the Copernicus red spot can be a residual of a red material (possibly rhyolite) extrusion that was involved in the impact process. The red material could have been partially melted, crushed, and ejected to the crater's north-western vicinity. The described red asymmetry of the Copernicus ejecta can be related to the eccentricity, relative to the extrusion, of the impact and/or to the inclination of the impactor trajectory. The latter also is confirmed by an analysis of the region, which is based on the geological map shown in this paper.

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: Contribution No. 2386, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena 91109.

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Lunar red spots: Possible pre-mare materials

Abstract

Icarus

Geologic map of the near side of the moon

U.S. Geol. Survey Map 1–703

Lunar color boundaries and their relationship to topographic features

The Moon

Color differences on the lunar surface

Lunar spectral types

J. Geophys. Res.

Remote sensing of lunar surface mineralogy implications from visible and near infrared reflectivity of Apollo 11 samples

Electronic spectra of pyroxenes and the interpretation of telescopic spectral reflectivity curves on the moon

The distribution and ages of regional units in the lunar maria

Technique for rapid determination of relative ages of lunar areas using orbital photography

J. Geophys. Res.

Origin of the lunar regolith at Tranquility Base