Zeros of orthogonal polynomials

In light of global remotely sensed data, the igneous crust of the Moon can no longer be viewed as a simple, globally stratified cumulus structure, composed of a flotation upper crust of anorthosite underlain by progressively more mafic rocks and a residual-melt (KREEP) sandwich horizon near the base of the lower crust. Instead, global geochemical information derived from Clementine multispectral data and Lunar Prospector gamma-ray data reveals at least three distinct provinces whose geochemistry and petrologic history make them geologically unique: (1) the Procellarum KREEP Terrane (PKT), (2) the Feldspathic High-lands Terrane (FHT), and (3) the South Pole-Aitken Terrane (SPAT). The PKT is a mafic province, coincident with the largely resurfaced area in the Procellarum-Imbrium region whose petrogenesis relates to the early differentiation of the Moon. Here, some 40% of the Th in the Moon's crust is concentrated into a region that constitutes only about 10% of the crustal volume. This concentration of Th (average ∼5 ppm), and by implication the other heat producing elements, U and K, led to a fundamentally different thermal and igneous evolution within this region compared to other parts of the lunar crust. Lower-crustal materials within the PKT likely interacted with underlying mantle materials to produce hybrid magmatism, leading to the magnesian suite of lunar rocks and possibly KREEP basalt. Although rare in the Apollo sample collection, widespread mare volcanic rocks having substantial Th enrichment are indicated by the remote data and may reflect further interaction between enriched crustal residues and mantle sources. The FHT is characterized by a central anorthositic region that constitutes the remnant of an anorthositic craton resulting from early lunar differentiation. Basin impacts into this region do not excavate significantly more mafic material, suggesting a thickness of tens of kilometers of anorthositic crust. The feldspathic lunar meteorites may represent samples from the anorthositic central region of the FHT. Ejecta from deep-penetrating basin impacts outside of the central anorthositic region, however, indicate an increasingly mafic composition with depth. The SPAT, a mafic anomaly of great magnitude, may include material of the upper mantle as well as lower crust; thus it is designated a separate terrane. Whether the SPA basin impact simply uncovered lower crust such as we infer for the FHT remains to be determined.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/1999JE001103

Major lunar crustal terranes: Surface expressions and crust‐mantle origins

High-resolution gravity data obtained from the dual Gravity Recovery and Interior Laboratory (GRAIL) spacecraft show that the bulk density of the Moon's highlands crust is 2550 kilograms per cubic meter, substantially lower than generally assumed. When combined with remote sensing and sample data, this density implies an average crustal porosity of 12% to depths of at least a few kilometers. Lateral variations in crustal porosity correlate with the largest impact basins, whereas lateral variations in crustal density correlate with crustal composition. The low-bulk crustal density allows construction of a global crustal thickness model that satisfies the Apollo seismic constraints, and with an average crustal thickness between 34 and 43 kilometers, the bulk refractory element composition of the Moon is not required to be enriched with respect to that of Earth.

/pdf/the-crust-of-the-moon-as-seen-by-grail-1glf8bzv6k.pdf

The Crust of the Moon as Seen by GRAIL

Lunar sourcebook. A user's guide to the moon

http://www.geo.arizona.edu/%7Ereiners/Leeetal2009.pdf

Constraints on the depths and temperatures of basaltic magma generation on Earth and other terrestrial planets using new thermobarometers for mafic magmas

We test the lunar dynamo hypothesis by modeling the magnetization directions of isolated crustal anomalies on the Moon. Although some of our modeled paleopole locations coincide with the current rotational axis of the Moon, the ensemble trace out a great circle from the north to south pole along 90°W and 90°E longitude. This behavior could be a result of a circulating dipole axis, true polar wander, or a predominantly quadrupolar field. We are currently implementing Parker’s [1] method for calculating magnetization directions in order to assess the uniqueness of these paleopole positions.

Testing the lunar dynamo hypothesis using global magnetic field data

The Asymmetric Cratering History of the Moon and Terrestrial Planets

Unresolved Questions, and Future Measurement Objectives Walter S. Kiefer, Shaopeng Huang, Clive Neal, and Mark Wieczorek. Lunar and Planetary Institute, Houston TX 77058, kiefer@lpi.usra.edu, Dept. Geological Sciences, University of Michigan, Ann Arbor MI 48109, Dept. Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame IN 46556, Institute de Physique du Globe de Paris, Paris France.

/pdf/the-thermal-structure-and-evolution-of-the-moon-apollo-heat-18dznyj0vy.pdf

Mark A. Wieczorek

Papers

Testing the lunar dynamo hypothesis using global magnetic field data

The Asymmetric Cratering History of the Moon and Terrestrial Planets

The Thermal Structure and Evolution of the Moon: Apollo Heat Flow Results, Unresolved Questions, and Future Measurement Objectives

Lunar Radioactive Heat Source Distribution and Magnetic Field Generation

The InSight VBB Seismometer: From Signal and Noise to Internal Structure.