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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
12.
Provenance of Block Fields Along Lunar Wrinkle Ridges French, Renee A.; Watters, Thomas R.; Robinson, Mark S.
Journal of geophysical research. Planets,
November 2019, 2019-11-00, 20191101, Volume:
124, Issue:
11
Journal Article
Peer reviewed
Open access
Block fields and associated relatively high reflectance material along wrinkle ridge summits are revealed in meter‐scale Lunar Reconnaissance Orbiter Camera images. Wrinkle ridges with block fields ...in Mare Australe, Crisium, Fecunditatis, Frigoris, Nubium, the northern half of Oceanus Procellarum, Serenitatis, and Tranquillitatis are evenly distributed, and block density generally increases with wrinkle ridge slope. The median cross‐sectional area (proxy for diameter) of the 1,368 blocks measured in this study is ~7 m2, and 75% of these blocks are ≤~14 m2. We propose that the largest variation in cross‐sectional area of the blocks is related to substrate physical properties of the mare basalt and not a function of the slope on which they occur, suggesting that physical properties rather than slope are a stronger control on block size. The maximum length of blocks may constrain the minimum basalt flow thickness or joint width; our block measurements suggest basalt flows ~2–14 m thick, agreeing with previous estimates. The data suggest that blocks originate from mare basalt layers that buckle and break as a result of movement along ridge‐forming thrust faults. High reflectance material associated with wrinkle ridge blocks likely represents freshly exposed rock and soil. Meter‐scale blocks may erode relatively quickly due to collisional disruption, indicating recent downslope movement of regolith exposing preexisting blocks or blocks formed and exposed by recent activity on ridge‐forming faults.
Plain Language summary
Wrinkle ridges are contractional tectonic landforms found in mare basalts. First detected by telescope observation of the lunar nearside, they have been extensively photographed and imaged by pre‐Apollo and post‐Apollo lunar missions. One characteristic of lunar wrinkle ridges that went undetected until the Lunar Reconnaissance Orbiter mission was the presence of thousands of boulders or blocks found in fields on the ridge slopes. In this study, Lunar Reconnaissance Orbiter Camera images were used to analyze the spatial distribution of wrinkle ridge block fields in all the major nearside mare, and over a thousand individual blocks were measured. We find that the median cross‐sectional area of the measured blocks is about 7 m2. The dimension of measured blocks is consistent with estimates of the thickness of basalt flows. This suggests that the blocks originate from individual mare basalt flows that buckle and break due to the contraction and uplift that forms the wrinkle ridges. Meter‐sized blocks are expected to erode away in about 40 to 300 Ma under lunar conditions. This suggests that preexisting blocks have been recently exposed by downslope movement of regolith, or the blocks have been formed by recent tectonic activity in the ancient lunar mare.
Key Points
Blocky wrinkle ridges are roughly evenly distributed throughout the maria, and block density generally increases with slope
Blocks are likely formed by deformation of mare basalts during wrinkle ridge formation
Block size and high reflectance material in block fields suggest activity within the last 300 Ma
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The gravity aspects for the Moon (the gravity disturbance, the Marussi tensor, two gravity invariants, dimensionality ratio, the strike angles, and the virtual deformations), all combined with ...magnetic anomalies and detailed surface topography, allow new views of specific locations on the Moon. Using these new gravity quantities, we hypothesize the following for several features on the Moon. A dike-like intrusion (exceeding ~100 km in length) from inside to outside of the Clavius crater likely solidified at the time of the existence of lunar dynamo. Mare Crisium analyses show a specific distribution of faulting across the mare. The same size impacts, Crisium and Clavius, present the dilatational deformation that is smoother for Crisium, while Clavius is under variable concentric compression due to an uplift of denser rock. Mare Orientale deformation not only confirmed the prior finding of the near surface faults, but also reveals a nature of the faulting (expansion vs compression blocks). Magnetic analyses of related lunar anomalies constrain mascon extent under the Copernicus structure and outline contraction areas from cooling of the upwelled mantle material. Mare Imbrium impact event has demagnetized regolith along with the Copernicus crater using a novel mechanism of shock propagation while plasma demagnetization. Clavius' magnetic field reveals magnetization that is likely more than four billion years old. Mare Crisium impact has a unique magnetization signature by impact related transient field. Mare Orientale showed, for the first-time, rippling-like effect of the Moon's mantle. This process of upwelled rippled mantle allows efficient demagnetization of the Orientale basin. For the first time, the application of the gravity aspects has been extended from the Earth to the Moon. This approach opens a new and inspiring field of planetary studies and point to otherwise hardly detectable phenomena. More detailed studies should follow.
•New method reveals properties of the lunar surface modified by impact cratering•Gravity aspects for the Moon computed and evaluated for the first time•Gravity and magnetic signal of impact craters, maria and catenae tested•Magnetic anomalies computed and tentatively interpreted•Several findings confirming previous works and new observations presented
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Dopamine (DA), via dopaminergic neurons, modulates prolactin secretion from the pituitary by tonic inhibition of lactotropes. Previously, kisspeptin (Kp) attenuated the prolactin response to the DA ...antagonist, sulpiride, in diestrous mares and enhanced the prolactin response to sulpiride in estradiol-primed mares. Whether or not Kp can modulate prolactin by acting on DA neurons has yet to be described in horses; therefore, the objective of this study was to determine if Kp and kisspeptin receptor (Kiss1r) co-localize with DA neurons, thus providing evidence for a direct action of Kp on DA neurons. Hypothalami from 4 light-horse diestrous mares, aged 6 to 21, were obtained following euthanasia. Mares were determined to be diestrous based on presence of corpora lutea and progesterone concentrations. Immediately following euthanasia, the carotid artery was perfused with sodium nitrite and 4% paraformaldehyde before decapitation and dissection of hypothalami. Immunofluorescent double labeling of tyrosine hydroxylase (TH) and Kp, as well as TH and Kiss1r, was carried out on paraffin-embedded hypothalamic sections using validated antibodies. Whole slide scans were analyzed for double-labeled cells; percentage of DA neurons colocalized with Kp-ir cell bodies and fibers, as well as percentage of DA neurons colocalized with Kiss1r-ir cells, were calculated and averaged for multiple sectionsper horse from rostral to caudal throughout the hypothalamus. Similarly, percentage and number of Kp or Kiss1r-ir cell bodies co-colocalized with TH-ir cells were calculated for different hypothalamic regions: the arcuate nucleus (Arc), ventromedial nucleus (VMH), and dorsomedial nucleus (DMH), and compared using Kruskall Wallis with Dunn's multiple comparison test. DA neurons were observed lining the third ventricle and spread from the Arc to the DMH, with little to none present in the posterior nucleus. TH and Kp expressing cell bodies co-localized between 8 and 30%, with less in the caudal DMH (P ≤ 0.05) compared with the Arc. Kp fibers synapsed with TH-expressing cell bodies at a low percentage, between 0 and 16%, with less connections in the DMH (P ≤ 0.05) than in the ARC. TH and Kiss1r co-localized between 20 and 65%, with similar distribution throughout the Arc, VMH, and DMH in rostral sections. In caudal hypothalamic sections, co-localization was greater (P ≤ 0.05) in the Arc compared with other areas that express lower or no DA neurons. Co-localization of TH and Kiss1r as well as co-localization and synaptic attachment of Kp on TH positive cells suggests a direct effect of kisspeptin on DA neurons to modulate prolactin release.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The Lunar Radar Sounder (LRS) onboard Kaguya (SELENE) detected widespread horizontal reflectors under some nearside maria. Previous studies estimated that the depths of the subsurface reflectors were ...up to several hundreds of meters and suggested that the reflectors were interfaces between mare basalt units. The comparison between the reflectors detected in the LRS data and surface age maps indicating the formation age of each basalt unit allows us to discuss the lower limit volume of each basalt unit and its space and time variation. We estimated volumes of basalt units in the ages of 2.7 Ga to 3.8 Ga in the nearside maria including Mare Crisium, Mare Humorum, Mare Imbrium, Mare Nectaris, Mare Serenitatis, Mare Smythii, and Oceanus Procellarum. The lower limit volumes of the geologic units estimated in this study were on the order of 103 to 104 km3. This volume range is consistent with the total amount of erupted lava flows derived from numerical simulations of thermal erosion models of lunar sinuous rille formation and is also comparable to the average flow volumes of continental flood basalt units formed after the Paleozoic and calculated flow volumes of Archean komatiite flows on the Earth. The lower limits of average eruption rates estimated from the unit volumes were on the order of 10−5 to 10−3 km3/yr. The estimated volumes of the geologic mare units and average eruption rate showed clear positive correlations with their ages within the same mare basin, while they vary among different maria compared within the same age range.
Key Points
Volumes of mare basalt units in the ages of 2.7 Ga to 3.8 Ga were estimated
The volumes of the geologic units were of the order of 103 to 104 km3
The average eruption rates were of the order of 10−5 to 10−3 km3/yr
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•Chang'e-5 mission is China's first lunar sample return mission.•The Chang'e-5 landing site lies within northern Oceanus Procellarum.•Em4 basalts are among one of the youngest mare basalts on the ...Moon.•Samples from Em4 will address lots of fundamental scientific questions.
Chang'e-5, China's first lunar sample return mission, is targeted to land in northern Oceanus Procellarum, within a region selected on the basis of 1) its location away from the Apollo-Luna sampling region, 2) the presence of the Procellarum KREEP Terrane (PKT), 3) the occurrence of one of the youngest lunar mare basalts (Em4), and 4) its association with Rima Sharp. In order to provide context for returned sample analyses, we conducted a comprehensive study of the regional and global settings, geomorphology, composition, mineralogy, and chronology of the Em4 mare basalts. Superposed on Imbrian-aged low-Ti basalts, Em4 covers 37,000 km2 and is composed of Eratosthenian-aged (∼1.53 Ga), high-Ti basalts with a mean thickness of ∼51 m and a volume between ∼1450 and 2350 km3. Minor variations in TiO2 and FeO abundance occur within the unit and the thorium content averages ∼6.7 ppm, typical of PKT mare basaltic regolith. No specific source vents (e.g., fissures, cones, domes) were found within the unit. We show that Rima Sharp is actually composed of three major rilles, whose source vents are located outside of, and which flow into, and merge in Em4, suggesting that they may be among the sources for Em4. Regolith thickness averages ∼7 m and there is abundant evidence for vertical and lateral mixing; the most likely sources of distal ejecta are Aristarchus, Harpalus, and Sharp B craters. Returned samples from local and distant materials delivered by impact will thus provide significant new insights into lunar geochronology, inner Solar System impact fluxes, the age of very young mare basalts, the role of the PKT in the generation of mare basalts, the role of sinuous rilles in lava flow emplacement, and the thermal evolution of the Moon.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The Marginis-Smythii region of the eastern limb of the Moon is a unique geological setting with the presence of equally widespread volcanism both inside and outside of an impact basin. Mare Marginis ...(13.3°N, 86.1°E) is a large mare deposit lying north of the pre-Nectarian Smythii Basin (13.3°N, 86.1°E). The basalts from Mare Marginis are deposited in a topographically low area outside an impact basin, i.e. the Smythii Basin. The Marginis-Smythii region is important to understand the geological controls on basalt emplacement on the Moon. In this study, we carry out a detailed investigation of the Mare Marginis and Mare Smythii basalts using the Moon Mineralogy Mapper (M3) data to understand the compositional diversity of the basalt deposits. Our study reveals that the basalts in the Mare Marginis can be divided into two distinct units: i) the central and eastern Marginis basalts that are spectrally similar to the Mare Smythii basalts, and ii) the western lacus, described as Margins west which is a small basalt deposit in the western fringes of Mare Marginis having a spectral composition different from the rest of Mare Marginis and Mare Smythii. We report that the volcanism in this compositionally distinct unit of Marginis west occurred up to ∼3.1 Ga when volcanism was still active in the Smythii Basin. We found that the volcanism in Mare Marginis was influenced by both; Crisium and Smythii Basins implying that the pre-existing structures in the lunar crust generated by large-scale impacts play an important role in the volcanism on the Moon.
•A compositionally distinct volcanic unit, ‘Marginis west’, has been identified in the study.•Volcanism in the Mare Marginis west continued till ∼3.1 Ga alongside volcanism in the Smythii Basin.•The basalts of Marginis west are a case of volcanism along the ring of the Crisium Basin.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
By using high-resolution altimetric measurements of the Moon, we produced a catalog of all impact craters ≥20 kilometers in diameter on the lunar surface and analyzed their distribution and ...population characteristics. The most-densely cratered portion of the highlands reached a state of saturation equilibrium. Large impact events, such as Orientale Basin, locally modified the prebasin crater population to ~2 basin radii from the basin center. Basins such as Imbrium, Orientale, and Nectaris, which are important stratigraphie markers in lunar history, are temporally distinguishable on the basis of crater statistics. The characteristics of pre-and postmare crater populations support the hypothesis that there were two populations of impactors in early solar system history and that the transition occurred near the time of the Orientale Basin event.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
19.
The Lakes and Seas of Titan Hayes, Alexander G
Annual review of earth and planetary sciences,
01/2016, Volume:
44, Issue:
1
Journal Article
Peer reviewed
Open access
Analogous to Earth's water cycle, Titan's methane-based hydrologic cycle supports standing bodies of liquid and drives processes that result in common morphologic features including dunes, channels, ...lakes, and seas. Like lakes on Earth and early Mars, Titan's lakes and seas preserve a record of its climate and surface evolution. Unlike on Earth, the volume of liquid exposed on Titan's surface is only a small fraction of the atmospheric reservoir. The volume and bulk composition of the seas can constrain the age and nature of atmospheric methane, as well as its interaction with surface reservoirs. Similarly, the morphology of lacustrine basins chronicles the history of the polar landscape over multiple temporal and spatial scales. The distribution of trace species, such as noble gases and higher-order hydrocarbons and nitriles, can address Titan's origin and the potential for both prebiotic and biotic processes. Accordingly, Titan's lakes and seas represent a compelling target for exploration.
Glucocorticoids (GCs) are known to play an important role in maintaining basal and stress-related homeostasis by interacting with endocrine mediators and prostaglandins (PGs). Although a growing body ...of evidence shows that GCs exert their regulatory action at a multitude of sites in the reproductive axis through corticosteroid receptors, little is known about the direct role of cortisol, an active form of GCs, in the equine endometrium. Thus, the study aimed to determine the effect of cortisol on PGF2α synthesis in the endometrial tissue and cells in vitro. In Exp.1, the immunolocalization and the expression of the glucocorticoid receptor (GCR) in the endometrium throughout the estrous cycle were established. In Exp. 2 and 3, the effects of cortisol on PGF2α secretion and transcripts associated with the arachidonic acid (AA) cascade in endometrial tissues, and cells were defined. Endometrial tissues obtained from the early, mid, and late luteal phases and the follicular phase of the estrous cycle were exposed to cortisol (100, 200, and 400 nM) for 24 h. Endometrial epithelial and stromal cells (early phase of estrous cycle) were exposed to cortisol (100 nM) for 24 h. Then, PGF2α secretion and transcripts associated with the AA cascade (PLA2G2A, PLA2G4A, PTGS2, and PGFS) were assessed. GCR was expressed in the cytoplasm and the nucleus in the luminal and glandular epithelium as well as in the stroma. Endometrial GCR protein abundance was up-regulated at the late luteal phase compared to the mid-luteal phase of the estrous cycle. Cortisol dose-dependently decreased PGF2α secretion, PLA2G2A and PLA2G4A transcripts in endometrial tissues. Additionally, cortisol treatment decreased PGF2α secretion from endometrial epithelial and stromal cells. Moreover, it affected PLA2G2A, PLA2G4A, and PTGS2 transcripts in endometrial stromal cells. These findings suggest that cortisol suppresses the synthesis of PGF2α by affecting the AA cascade in the equine endometrium during the estrous cycle.
•GCR protein abundance was up-regulated at the late luteal phase.•Cortisol decreased PGF2α secretion from endometrial tissue and cells.•Cortisol decreased PLA2G2A and PLA2G4A transcripts in endometrial tissues.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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