Showing papers by "Mark A. Wieczorek published in 2010"

Structure and Formation of the Lunar Farside Highlands

Abstract: The formation of the lunar farside highlands has long been an open problem in lunar science. We show that much of the topography and crustal thickness in this terrain can be described by a degree-2 harmonic. No other portion of the Moon exhibits comparable degree-2 structure. The quantified structure of the farside highlands unites them with the nearside and suggests a relation between lunar crustal structure, nearside volcanism, and heat-producing elements. The farside topography cannot be explained by a frozen-in tidal bulge. However, the farside crustal thickness and the topography it produces may have been caused by spatial variations in tidal heating when the ancient crust was decoupled from the mantle by a liquid magma ocean, similar to Europa's present ice shell.

Testing the lunar dynamo hypothesis using global magnetic field data

Abstract: 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.

The Interior Structure of the Moon: What Does Geophysics Have to Say?

Abstract: Geophysical data obtained from orbit and surface stations show that the Moon is a differentiated body possessing a crust, mantle, and core. The crust is on average about 40 km thick, and impact events with asteroids and comets have excavated materials to great depths within the crust. Moonquakes that are correlated in time with Earth-raised tides occur about halfway to the center of the Moon and suggest that the deepest portion of the mantle might be partially molten. The lunar core is relatively small in comparison with the cores of the terrestrial planets, with a size less than one-quarter of the Moon’s radius.

Testing the lunar dynamo hypothesis using global magnetic field data

Abstract: 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.

Surface Roughness and Rock Population of the Lunar Regolith: Results from 70-cm Arecibo Radar Observations

Abstract: The Earth-based 70-cm Arecibo radar data of the lunar nearside are used to study the surface roughness and abundance and size of the buried rocks at 7 Lunar Orbiter sites and Apollo 12 landing sites. Using these results in combination with global geochemical maps, and known correlations between composition, density, and dielectric properties, these results will be extended to invert for a regolith thickness map over lunar nearside hemisphere.