Is the Lunar Magnetic Field Correlated With Gravity or topography?

Abstract

Magnetic field measurements made from orbit show that there are strong magnetic anomalies on the Moon, but many of these show no clear correlation with known geological processes. Given that the primary magnetic carrier on the Moon is metallic iron, which is considerably denser than the silicate minerals that make up the crust, we might expect that there would be a correlation between the magnetic field and gravity. If the magnetic anomaly were related to iron-rich impact ejecta, there might also be a correlation between the magnetic field and topography. We use magnetic field, topography, and gravity data to test whether such correlations exist. Our results demonstrate that some magnetic anomalies show statistically significant positive correlations with free-air gravity and topography, and the magnetic sources within these regions could potentially be iron-rich impact ejecta. In a few cases, the magnetic anomalies show statistically significant positive correlations with Bouguer gravity, implying that the magnetic anomalies are associated with density anomalies within either the crust or upper mantle. The origin of the vast remainder of lunar magnetic anomalies remains enigmatic. Plain Language Summary Although the Moon does not have a global magnetic field like theEarth at the present time, portions of the lunar crust are found to be strongly magnetized. The origin of these crustal magnetic anomalies is uncertain since many of these anomalies show no clear correlation with geological features. Here we test whether these magnetic anomalies are related to topography or gravity in order to constrain the origin of these anomalies. We found that in some cases, the magnetic anomalies could be related to iron-rich impact ejecta. In a smaller number of cases, some magnetic anomalies might be related to subsurface density anomalies.

Depth of Martian Magnetization From Localized Power Spectrum Analysis

“…In contrast, shallow magnetic sources might be associated with impact basin ejecta, surface lava flows, or impact melt sheets. Previous studies on Earth's moon have found that portions of the magnetic sources lie close to the surface (Wieczorek, 2018) and are correlated with surface topography (Gong & Wieczorek, 2020), which is consistent with having an origin as iron-rich impact ejecta. In other regions of the lunar highland crust the magnetization was found to be deep, and likely to have formed with the crust during the initial differentiation of the Moon (Wieczorek, 2018).…”

“…Performing a grid search over the inversion parameter space, the best fitting parameters that minimize were obtained. After obtaining the best fitting values, a Monte Carlo technique was then employed to quantify the 1‐ uncertainties of each parameter (see Gong & Wieczorek, 2020; Wieczorek, 2018). In this step, a global magnetic field power spectrum was first calculated using the best fitting parameters.…”

Ultraviolet and magnetic perspectives at Reiner Gamma and the implications for solar wind weathering

“…Initial data from magnetometers carried by the Apollo missions revealed weak, patchy surface magnetism on the Moon (e.g., Coleman et al, 1972;Dyal et al, 1974), and recent missions such as NASA's Lunar Prospector (LP) and JAXA's Kaguya confirmed that magnetic anomalies are distributed across both maria and highlands, with the highest concentration of anomalies occurring on the far side of the Moon on the outskirts of and within the South-Pole Aitken basin (Lin et al, 1998;Tsunakawa et al, 2010). While the origin of these MAs is currently unknown, several studies have suggested that the global distribution (Figure 2), indicates that MAs are a form of natural remanent magnetization within crustal sources (e.g., Sonett & Mihalov, 1972;Halekas et al, 2001;Hood et al, 2001;Gong & Wieczorek, 2020).…”

Constraints on the Spatial Distribution of Lunar Crustal Magnetic Sources From Orbital Magnetic Field Data

“…Previous studies have attempted to constrain the magnetization underlying the magnetic anomalies by relying on available regional geological context, like associated albedo anomalies, also known as swirls (Garrick‐Bethell & Kelley, 2019; Hemingway & Tikoo, 2018; Hood & Schubert, 1980), topography (Oliveira et al., 2017), and gravity (Gong & Wieczorek, 2020; Kelley & Garrick‐Bethell, 2020). Swirls are always associated with magnetic anomalies and are thought to be the result of the crust being locally shielded from the solar wind by the crustal magnetic field.…”