Mare Vaporum Research Articles

Chronology, composition, and mineralogy of mare basalts in the junction of Oceanus Procellarum, Mare Imbrium, Mare Insularum, and Mare Vaporum

The timeline of volcanic activity is critical for constraining the thermal evolution of the Moon. The spatial extents of mare basalts, major products of lunar volcanism, have been precisely extracted from LROC (Lunar Reconnaissance Orbiter Camera) image mosaics. With the maria extents newly extracted from LROC mosaics, we found that a large area of mare basalts in the junction of Oceanus Procellarum, Mare Imbrium, Mare Insularum, and Mare Vaporum (the PIV region) has not yet been dated. This study analysed the chronology, composition, and mineralogy of the PIV region, aiming to finish the picture of basaltic volcanism in the Procellarum region, which is a key puzzle of our global geological mapping of the Moon. According to the topographical, spectral, and compositional characteristics, mare units of the PIV region are defined, and the crater size frequency distribution is measured. The primary craters with diameters >0.1 km in the PIV region are measured, and the absolute model ages of basalt units between ∼3.78 Ga and ∼1.71 Ga are derived. Most western PIV basalt units are Eratosthenian-aged, while eastern units mostly formed in the Imbrian period. The spectra of 4965 small impact craters are extracted to interpret the mineral compositions of the PIV basalt units using Chandrayaan-1 Moon Mineralogy Mapper data. Using a Modified Gaussian Model, the reflectance spectra are deconvoluted, and the obtained modal proportions of mafic minerals show low olivine and high low-Ca pyroxene abundances in the eastern PIV region, while the western region features high olivine and calcic pyroxene concentrations. Three episodes of volcanic events occurring in the PIV region are identified. The first (main) occurred at approximately 3.5 Ga (Late Imbrian), with erupted lava flows with less evolved compositions covering most of the PIV area. The peak of volcanic activity in the Eratosthenian period occurred around 2.5 Ga, where mare basalts with moderately evolved compositions and mineralogy were formed. The last major eruption occurred at approximately 1.8 Ga, forming mare basalts with highly evolved compositions.

Characterizing southern portion of Mare Vaporum with improved Chandrayaan-1 M3 data

We investigate a southern portion of Mare Vaporum using Chandrayaan-1 M3 images for which we suppress striped noise. Additional data processing allows us to analyze such spectral parameters as the depths and positions of the absorption bands near 1 and 2 μm. Mineral types were mapped using the cluster analysis of Adams diagram for pyroxenes. We inspected, in particular, the areas of pyroclastic deposits around the crater Hyginus and small areas in the crater which have the 2 μm band shifted to longer wavelengths. We examined the areas with phase-ratio analysis of LROC NAC images: the areas associated with clinopyroxenes are distinguished both in albedo and phase-ratio (56°/23°) images, perhaps, having higher roughness than surrounding surface; Whereas the areas associated with pyroclastic glasses does not seen neither in albedo nor phase-ratio images.

Morphological and Chronological Mapping of Manilius Crater Region Using Chandrayaan-1 Data Sets

Fine-resolution morphological mapping aided by ortho-images and digital elevation model from Chandrayaan-1 Terrain Mapping Camera and 3D GIS visualization has revealed scientifically diverse characteristics of lunar surface features, due to unique topographical significance of morphological features, i.e., highlands, basaltic plains and craters, which are very well manifested in 3D GIS environment. The distribution of various morphological features provides insights into the sequential evolution and surface process of the study area. The highland region represented by the Fra Mauro formation in the study area exhibits high albedo with distinct topography. The northern part of the study area falls in the southern part of major basin Serenitatis, and exhibits the dark mantling material with low albedo. The morphological features, i.e., wrinkle ridges and rilles, indicate volcanic flow events consequence to the loading of basaltic materials in the interior of the Serenitatis and Imbrium Basins and related extensional failure. The Manilius crater, which occupies the central part of the study area, is a complex crater with a central peak and asymmetric ejecta deposit. The ages of the major surficial features were determined based on size, frequency and distribution pattern of craters using crater size-frequency distribution model. Age of the Fra Mauro highland, Manilius crater, Mare Serenitatis and Mare Vaporum is, respectively, 3.9, 3.5, 2.8 and 1.7 Ga years, indicating that the lunar surface of this region evolved in Imbrian to Eratosthenian age of lunar selenological timescale.

MINERAL MAPPING USING CHANDRAYAAN-1 HYPERSPECTRAL (HYSI) DATA FROM MARE VAPORUM

Abstract. The imaging spectroscopy offers an opportunity to map and discriminate different minerals on the lunar surface which further helps to understand the origin, evolution process, and the crustal composition on the surface of the moon. Compositional mapping of the lunar surface is considered as a standard approach for mineral mapping. This paper reports surface mineralogy of the lunar surface from Mare Vaporum using Chandrayaan-1 Hyperspectral remotely sensed data from HySi sensor. False color composite is created using different band shaping algorithms like band strength; band curve and band tilt parameters at crucial wavelength for spatial analysis. The Spectral analysis has been done by deriving reflectance spectra at varying locations from the area under study. The Study shows the mineral map with different categories of minerals which are high-Ca pyroxene and/or olivine and low Ca-pyroxene. However because of the limited spectral coverage of HySi, data at the longer wavelengths required to discriminate among different group of minerals.

The relationship between radar scattering and surface roughness of lunar volcanic features

AbstractLunar roughness measurements derived from the Lunar Orbiter Laser Altimeter are compared to 12.6 cm wavelength radar data collected by the Miniature Radio Frequency instrument and 70 cm wavelength radar data collected by the Arecibo Observatory. These data are compared to assess how surface and subsurface roughness are correlated and affected by parameters including age and composition at length scales between 0.1 and 100 m. A range of features are analyzed including volcanic domes (Marius Hills, Rümker Hills, Gruithuisen, and Mairan Domes); mare (Imbrium, Serenitatis, and Oceanus Procellarum); pyroclastic dark mantle deposits (Sinus Aestuum, Sulpicius Gallus, and Mare Vaporum); and two young craters (Copernicus and Tycho). Statistically significant positive correlations exist between topographic roughness and both P‐ and S‐band circular polarization ratios. The strongest correlation is observed at the longest length scales. Correlations weaken as length scales become less similar, potentially due to distinct processes controlling surface modification. Roughness is not significantly correlated with local slope. Although the Marius Hills are compositionally distinct from the Gruithuisen and Mairan domes, they are indistinguishable in roughness characteristics. Conversely, the Rümker Hills, mare, and dark mantle deposits are smoother at the length scales examined, possibly due to fine‐grained mantling of regolith or pyroclastic deposits. The floor and ejecta of Tycho are the roughest surfaces measured in this study, while the floor and ejecta of Copernicus overlap the roughness distribution of the volcanic features. This study shows that many factors control the evolution of roughness over time on various length scales.

On a volcanic construct and a lunar pyroclastic deposit (LPD) in northern Mare Vaporum

In this study we examine a lunar pyroclastic deposit (LPD) identified using LROC WAC images, Selene-1 (Kaguya) and Clementine multispectral data, the Chandryann-1׳s Moon Mineralogy Mapper (M3), and the LROC WAC-based GLD100 DTM. Selene-1 (Kaguya) and Clementine albedo imagery indicates the presence of pyroclastic deposits located some 40km to the west-southwest of the crater Yangel in Mare Vaporum, and to the southeast of Sinus Fidei (16.42°N and 3.26°E), and associated with a dome like structure. This dome, which we term Yangel 1 (Ya1), lies immediately to the south of a mare flooded crater which is approximately 7.5km in diameter, and is partially buried along its southern rim by the domes northern flank. With a diameter of 5.2km, and a height of 620m, the dome Ya1 exhibits evidence of pyroclastic volcanic deposits, both on its surface and peripherally. The current study discusses the dome Ya1, the associated deposits and possible relationship between them.

Ages and stratigraphy of lunar mare basalts in Mare Frigoris and other nearside maria based on crater size‐frequency distribution measurements

We report on ages derived from impact crater counts for exposed mare basalt units in the northern part of the lunar nearside hemisphere (Mare Frigoris), the eastern and northeastern part of the nearside hemisphere (Lacus Temporis, Joliot, Hubble, Goddard, Mare Marginis, and Mare Smythii), the central part of the nearside hemisphere (Palus Putredinis, Mare Vaporum, and Sinus Medii), and the southwestern part of the nearside hemisphere (Grimaldi, Crüger, Rocca A, Lacus Aestatis, and Schickard). In Mare Frigoris, we dated 37 basalt units, showing ages from 2.61 to 3.77 Gyr, with most units being formed in the late Imbrian period between 3.4 and 3.8 Gyr ago. In Mare Vaporum we dated six spectrally homogeneous units that show model ages of 3.10 to 3.61 Gyr. Our model ages of basalts in Mare Marginis range from 3.38 to 3.88 Gyr and are mostly older than basalts in Mare Smythii (3.14–3.48 Gyr). The model ages of four units in Sinus Medii indicate that the basalts in this region formed 3.63 to 3.79 Gyr ago. We find an excellent agreement of our crater size‐frequency model ages of the Palus Putredinis area, which contains the Apollo 15 landing site, with the radiometric ages of Apollo 15 samples. According to our crater counts, basalts in Palus Putredinis are 3.34 Gyr old and this compares favorably with the radiometric ages of 3.30–3.35 Gyr of the olivine‐normative and quartz‐normative basalts of the Apollo 15 landing site. Lacus Aestatis is a small irregular‐shaped mare patch in the southwestern nearside and shows an Imbrian age of 3.50 Gyr; basalts in Lacus Temporis in the northeastern nearside formed between 3.62 and 3.74 Gyr ago and are, therefore, older than the basalts in Lacus Aestatis. We found that basalts in craters of the southwestern nearside (Schickard, Grimaldi, Crüger, and Rocca A) are also mostly younger than basalts in craters of the northeastern nearside (Hubble, Joliot, and Goddard). While basalt ages vary between 3.16 and 3.75 Gyr in the southwest, basalts in the northeast are 3.60–3.79 Gyr old. These results confirm and extend the general distribution of ages of mare basalt volcanism and further underline the predominance of older mare basalt ages in the eastern and southern nearside and in patches of mare peripheral to the larger maria, in contrast to the younger basalt ages on the western nearside (Oceanus Procellarum).

Radar remote sensing of pyroclastic deposits in the southern Mare Serenitatis and Mare Vaporum regions of the Moon

We use polarimetric radar observations to study the distribution, depth, and embedded rock abundance of nearside lunar pyroclastic deposits. Radar images were obtained for Mare Vaporum and the southern half of Mare Serenitatis; the imaged areas contain the large Rima Bode, Mare Vaporum, Sulpicius Gallus, and Taurus‐Littrow pyroclastic deposits. Potential pyroclastic deposits at Rima Hyginus crater, the Tacquet Formation, and a dome in Mare Vaporum are also included. Data were acquired at S band (12.6 cm wavelength) using Arecibo Observatory and the Green Bank Telescope in a bistatic configuration. The S band images have resolutions between 20 and 100 m/pixel. The pyroclastic deposits appear dark to the radar and have low circular polarization ratios at S band wavelengths because they are smooth, easily penetrable by radar waves, and generally contain few embedded blocks. Changes in circular polarization ratio (CPR) across some of the pyroclastic deposits show areas with increased rock abundance as well as deposits that are shallower. Radar backscatter and CPR maps are used to identify fine‐grained mantling deposits in cases where optical and near‐infrared data are ambiguous about the presence of pyroclastics. The Tacquet Formation in southern Serenitatis, areas near Hyginus crater, and a dome in Mare Vaporum have lower‐backscatter cross sections than would be expected for mare basalts of similar estimated titanium content. Combined with very low CPR values, this is strong evidence that these areas are covered in fine‐grained pyroclastic mantling material.

Petrography and geochemistry of five new Apollo 16 mare basalts and evidence for post‐basin deposition of basaltic material at the site

Abstract— We present the petrography and geochemistry of five 2–4 mm basalt fragments from the Apollo 16 regolith. These fragments are 1) a high‐Ti vitrophyric basalt compositionally similar to Apollo 17 high‐Ti mare basalts, 2) a very high‐Ti vitrophyric basalt compositionally similar to Apollos 12 and 14 red‐black pyroclastic glass, 3) a coarsely crystalline high‐Al basalt compositionally similar to group 5 Apollo 14 high‐Al mare basalts, 4) a very low‐Ti (VLT) crystalline basalt compositionally similar to Luna 24 VLT basalts, and 5) a VLT basaltic glass fragment compositionally similar to Apollo 17 VLT basalts. High‐Ti basalt has been reported previously at the Apollo 16 site; the other basalt types have not been reported previously. As there are no known cryptomaria or pyroclastic deposits in the highlands near the Apollo 16 site (ruling out a local origin), and scant evidence for basaltic material in the Apollo 16 ancient regolith breccias or Apollo 16 soils collected near North Ray Crater (ruling out a basin ejecta origin), we infer that the basaltic material in the Apollo 16 regolith originated in maria near the Apollo 16 site and was transported laterally to the site by small‐ to medium‐sized post‐basin impacts. On the basis of TiO2 concentrations derived from the Clementine UVVIS data, Mare Tranquillitatis (˜300 km north) is the most likely source for the high‐Ti basaltic material at the Apollo 16 site (craters Ross, Arago, Dionysius, Maskelyne, Moltke, Sosigenes, Schmidt), Mare Nectaris/Sinus Asperitatis (˜220 km east) is the most likely source for the low‐Ti and VLT basaltic material (craters Theophilus, Madler, Torricelli), and a large regional pyroclastic deposit near Mare Vaporum (˜600 km northwest) is the most likely source region for pyroclastic material (although no source craters are apparent in the region).

Imaging spectroscopy of selected regional dark mantle deposits of the Moon

We present the study of four surface units previously identified as dark mantle deposits on the Moon: Taurus Littrow, Sulpicius Gallus, Mare Vaporum and Rima Bode deposits. The data have been obtained at the 1.5 m telescope of Sierra Nevada Observatory (Granada, Spain) by using an imaging spectrometer working in the 0.4– 1.0 μm spectral range. Principal features of these geologic units are: (a) low albedo, (b) localization at the boundaries between highlands and maria, and (c) spectral properties similar to those of the associated mare lavas. The image cubes have been processed by means of two independent statistical methods: the principal components analysis and a supervised clustering technique (spectral angle mapper). Using these methods it has been possible to identify the areas covered by dark mantling material and to compare the different spectral properties of the four deposits. In particular, two different classes of the dark mantle deposits have been detected on the basis of the spectra. New areas in Sulpicius Gallus deposit having intermediate spectral behavior between highland soil and dark mantling material have been identified, probably due to a mixing of the two terrains.

Lunar regional dark mantle deposits: Geologic, multispectral, and modeling studies

Clementine five‐channel UV‐visible (UVVIS) data have been used to study seven regional dark mantle deposits (DMDs) on the Moon. The DMDs were mapped in distribution to determine their extent and stratigraphic relationship to other geologic units. Based upon the spectral properties for each DMD, the crystallization of the beads in each deposit was inferred and used to estimate cooling rates in the volcanic plumes that emplaced the deposits. Deposits with a high concentration of glasses reflect volcanic plumes that had low optical densities and high cooling rates, whereas deposits dominated by crystallized beads indicate plumes with slower cooling rates due to higher optical densities. Spectral data from each of the regional DMDs show that their glass:crystallized bead ratio can be estimated based upon their 415/750 and 750/950 nm values and comparison to laboratory spectra for the beads. Patches of young dark mantle in the Sinus Aestuum DMD represent one extreme with the bluest color (highest 415/750) and weakest glass band absorption (lowest 750/950) of all the DMDs. At the other extreme is the Aristarchus Plateau DMD with the reddest color and strongest glass band absorption. The other nearside DMDs, including Taurus‐Littrow, Sulpicius Gallus, Rima Bode, and Mare Vaporum lie between these two extremes due to intermediate mixtures of the crystallized beads and glasses with other local soils. The Orientale Ring DMD on the western limb is dominated by volcanic glasses and is spectrally similar to the localized DMDs found in Alphonsus crater. We have identified a central vent for the Orientale Ring DMD and model the eruption as degassing of a near‐surface dike to produce a 20‐km‐high umbrella‐shaped plume with ejection velocities of 360 m/s and deposition of the glasses at an average radius of 80 km from the vent. Although we cannot identify the exact sources for the other regional DMDs (probably because they are buried beneath younger mare), the eruptions most likely resulted from dikes breaching the surface and producing a volcanic plume dominated by larger (greater than submillimeter) hot clasts that formed mare and sinuous rules. The small percent of clasts that form the volcanic beads are carried by the expanding gas cloud to large distances, in some cases >100 km, to produce the observed continuous regional DMDs. The lack of basalt samples that can be petrologically related to the volcanic glasses may be a result of their spatial separation, with the basalts flowing into the basins while the beads are deposited both into the basins and on the adjacent highlands.

The Nature of the Lunar Maria.

It is shown that the surface temperature of the moon determined as a function of time by Pettit and Nicholson from infrared measurements in the lunar eclipse of June 14, 1927, is consistent only with a lunar surface composed of dust, in agreement with Wesselink's conclusion from data of Pettit for the later eclipse of October 27, 1939. The location of the observed area in the first eclipse permits direct inference of a dust cover for the lunar highlands. For the second eclipse, it is pointed out that a significant fraction (approximately one-quarter) of the projected receiver area covered virtually the whole extent of Mare Vaporum. From solutions of the equation of heat conduction obtained by others, the theoretical fall of temperature with time in the latter eclipse is calculated on the assumption that the surface of Mare Vaporum consists of bare rock but the surrounding highlands are covered with dust. The predicted march of the temperature differs so greatly from Pettit's determination that the presence of exposed lava on the surface is precluded, specifically for Mare Vaporum and by implication for any mare. The logical difficulties are discussed which this result poses for theories identifying the surfaces of the maria with lava flows. It is shown that the best over-all fit to Pettit's data for temperature versus time is obtained among suggested models of the lunar surface by one corresponding to Gold's theory that the maria are craters filled with dust. For this theory, no inconsistencies are found with respect to lunar temperatures inferred by infrared or microwave methods.

New Lunar Crater

I was much interested in the account which your last number (vol. xviii. p. 197) contained of the presumably new lunar crater discovered by Dr. Klein in the Mare Vaporum. Is it really necessary to ascribe the formation of such a crater to present volcanic action? It seems to me that this singular phenomenon of the birth of a new crater may be more likely owing to such action having, in long-past ages, left (as in all probability it would leave) extensive caverns beneath the visible surface of our satellite. Such caverns might, in consequence of the gradual changes which the action of the sun's rays, alternating with intense cold, must produce on the lunar rocks, occasionally give way. A crater-like cavity would then be caused on the moon's surface by this subsidence, such as are not unfrequently seen in mining districts where old workings have fallen in. The fact that the new crater is elliptical, and not round, seems to add to the probability of its having been caused by some such “settling” process. If the crater were produced by active volcanic agency, it would surely be circular, or nearly so. I do not find this mode of quasi-crater formation suggested in Nasmyth's book, nor, so far as I can remember, in any other. Is it not, however, a possible cause of change on the surface of our satellite?