Narendranath S.,Space Astronomy Group |
Narendranath S.,Rutherford Appleton Laboratory |
Athiray P.S.,Space Astronomy Group |
Sreekumar P.,Space Astronomy Group |
And 21 more authors.
Icarus | Year: 2011
The Chandrayaan-1 X-ray Spectrometer (C1XS) flown on-board the first Indian lunar mission Chandrayaan-1, measured X-ray fluorescence spectra during several episodes of solar flares during its operational period of ∼9. months. The accompanying X-ray Solar Monitor (XSM) provided simultaneous spectra of solar X-rays incident on the Moon which are essential to derive elemental chemistry. In this paper, we present the surface abundances of Mg, Al, Si, Ca and Fe, derived from C1XS data for a highland region on the southern nearside of the Moon. Analysis techniques are described in detail including absolute X-ray line flux derivation and conversion into elemental abundance. The results are consistent with a composition rich in plagioclase with a slight mafic mineral enhancement and a Ca/Al ratio that is significantly lower than measured in lunar returned samples. We suggest various possible scenarios to explain the deviations. © 2011 Elsevier Inc.
Joy K.H.,The Lunar and Planetary Institute |
Joy K.H.,NASA |
Joy K.H.,University of Manchester |
Nemchin A.,Curtin University Australia |
And 11 more authors.
Geochimica et Cosmochimica Acta | Year: 2014
Dhofar (Dho) 925, 961 and Sayh al Uhaymir (SaU) 449 are brecciated lunar meteorites consisting of mineral fragments and clasts from a range of precursor lithologies including magnesian anorthositic gabbronorite granulites; crystalline impact melt breccias; clast-bearing glassy impact melt breccias; lithic (fragmental) breccias; mare basalts; and evolved (silica-rich) rocks. On the similarity of clast type and mineral chemistry the samples are likely grouped, and were part of the same parent meteorite. Phosphate Pb-Pb ages in impact melt breccias and matrix grains demonstrate that Dho 961 records geological events spanning ~500. Ma between 4.35 and 3.89. Ga. These Pb-Pb ages are similar to the ages of 'ancient' intrusive magmatic samples and impact basin melt products collected on the lunar nearside by the Apollo missions. However, the samples' bulk rock composition is chemically distinct from these types of samples, and it has been suggested that they may have originated from the farside South Pole-Aitken impact basin (i.e., Jolliff et al., 2008). We test this hypothesis, and conclude that although it is possible that the samples may be from the South Pole-Aitken basin, there are other regions on the Moon that may have also sourced these complex breccias. © 2014 Elsevier Ltd.
Snape J.F.,University College London |
Joy K.H.,University College London |
Joy K.H.,Natural History Museum in London |
Joy K.H.,The Lunar and Planetary Institute |
And 3 more authors.
Meteoritics and Planetary Science | Year: 2011
Lunar meteorite Northeast Africa (NEA) 001 is a feldspathic regolith breccia. This study presents the results of electron microprobe and LA-ICP-MS analyses of a section of NEA 001. We identify a range of lunar lithologies including feldspathic impact melt, ferroan noritic anorthosite and magnesian feldspathic clasts, and several very-low titanium (VLT) basalt clasts. The largest of these basalt clasts has a rare earth element (REE) pattern with light-REE (LREE) depletion and a positive Euanomaly. This clast also exhibits low incompatible trace element (ITE) concentrations (e.g., <0.1ppm Th, <0.5ppm Sm), indicating that it has originated from a parent melt that did not assimilate KREEP material. Positive Eu-anomalies and such low-ITE concentrations are uncharacteristic of most basalts returned by the Apollo and Luna missions, and basaltic lunar meteorite samples. We suggest that these features are consistent with the VLT clasts crystallizing from a parent melt which was derived from early mantle cumulates that formed prior to the separation of plagioclase in the lunar magma ocean, as has previously been proposed for some other lunar VLT basalts. Feldspathic impact melts within the sample are found to be more mafic than estimations for the composition of the upper feldspathic lunar crust, suggesting that they may have melted and incorporated material from the lower lunar crust (possibly in large basin-forming events). The generally feldspathic nature of the impact melt clasts, lack of a KREEP component, and the compositions of the basaltic clasts, leads us to suggest that the meteorite has been sourced from the Outer-Feldspathic Highlands Terrane (FHT-O), probably on the lunar farside and within about 1000km of sources of both Low-Ti and VLT basalts, the latter possibly existing as cryptomaria deposits. © The Meteoritical Society, 2011.
Weider S.Z.,Birkbeck College |
Weider S.Z.,University College London |
Weider S.Z.,Rutherford Appleton Laboratory |
Crawford I.A.,Birkbeck College |
And 5 more authors.
Icarus | Year: 2010
We use multispectral reflectance data from the lunar Clementine mission to investigate the impact ejecta deposits of simple craters in two separate lunar mare basalt regions, one in Oceanus Procellarum and one in Mare Serenitatis. Over 100 impact craters are studied, and for a number of these we observe differences between the TiO2 (and FeO) contents of their ejecta deposits and the lava flow units in which they are located. We demonstrate that, in the majority of cases, these differences cannot plausibly be attributed to uncorrected maturity effects. These observations, coupled with morphometric crater relationships that provide maximum crater excavation depths, allow the investigation of sub-surface lava flow stratigraphy. We provide estimated average thicknesses for a number of lava flow units in the two study regions, ranging from ∼80m to ∼600m. In the case of the Serenitatis study area, our results are consistent with the presence of sub-surface horizons inferred from recent radar sounding measurements from the JAXA Kaguya spacecraft. The average lava flow thicknesses we obtain are used to make estimates of the average flux of volcanic material in these regions. These are in broad agreement with previous studies, suggesting that the variation in mare basalt types we observe with depth is similar to the lateral variations identified at the surface. © 2010 Elsevier Inc.