High‐Resolution Nighttime Temperature and Rock Abundance Mapping of the Moon Using the Diviner Lunar Radiometer Experiment With a Model for Topographic Removal

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Wrinkle ridges are the predominant tectonic structure on the nearside lunar maria. Although lunar wrinkle ridge formation began as early as ∼3.9–4.0 Ga, recent investigations have identified wrinkle ridges in the lunar maria that were tectonically active as recently as the Copernican period of lunar geologic history. Some of those geologically young wrinkle ridges were identified by the presence of dense fields of meter-scale boulders on their scarps and topographic crests. Other investigations have identified recently active lunar wrinkle ridges that lack the ubiquitous presence of boulder fields, thereby rendering the presence of boulder fields ambiguous in the search for ongoing tectonic activity on the Moon. Here we assess boulder populations associated with 1116 wrinkle ridge segments on the lunar maria that are inferred to be recently active (<1.5 Ga) based on their crisp morphologies and crosscutting relationships with small impact craters. We utilize data from the Lunar Reconnaissance Orbiter Mini-RF and Diviner Lunar Radiometer Experiment instruments to assess surface rock populations across these recently active structures. Our results indicate that, where present, meter-scale boulder fields are likely indicators of fault-slip-induced ground acceleration given the short lifespan of lunar surface boulders. However, elevated boulder populations are not observed on all recently active ridges analyzed here. This latter observation supports the notion that wrinkle ridge boulder fields are a nonunique indicator of recent tectonic activity. Furthermore, the spatial distribution of those boulder fields indicates that variable mare protolith properties may play a role in boulder field formation.

Section: Discussionmentioning

confidence: 99%

Section: Diviner Rock Abundancementioning

confidence: 99%

Lunar Boulder Fields as Indicators of Recent Tectonic Activity

Nypaver,

Watters,

Thomson

et al. 2024

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“…Some rayed craters in our catalog show only thermophysical rays (no albedo or maturity rays). Regolith thermophysical anomalies are dominantly produced by variations in density and degree of induration such as from the presence of small rocks (Bandfield et al 2011(Bandfield et al , 2014Powell et al 2023), with albedo variations playing little to no role. Thermophysical rays, therefore, likely represent a mixture of small rocks from primary ejecta and from secondary craters, and thus they form an important part of the continuum of distal impact products whose end-members are represented, respectively, by albedo-only variations and large rocks near crater rims.…”

Section: What Are Rays?mentioning

confidence: 99%

“…The thermophysical properties of the lunar regolith can be characterized using nighttime brightness temperature measurements from the LRO Diviner thermal radiometer (Paige et al 2009). Nighttime brightness temperatures are dominantly controlled by the temperature-dependent thermal inertia of lunar surface materials (Vasavada et al 1999;Bandfield et al 2011;Vasavada et al 2012;Hayne et al 2017), with smaller contributions from meter-scale topography (Powell et al 2023). To first order, the average nighttime brightness temperature can be approximated as a weighted average of the radiance contributions from two end-member components: meter-scale or larger rocks or other indurated materials, which radiate at high temperatures through the lunar night, and fine regolith materials, which cool rapidly after lunar sunset.…”

Section: Thermophysical Data Setsmentioning

confidence: 99%

The Population of Young Craters on the Moon: New Catalog and Spatial and Temporal Analysis

Ghent,

Costello,

Parker

2024

We present a new catalog of the Moon’s rayed and rocky craters from 5 to 130 km in diameter. Using data from the Lunar Reconnaissance Orbiter and the JAXA Kaguya/Selene missions, we identify 571 unique craters with albedo, maturity, and/or thermophysical rays, or rocky ejecta, or all of these, located between 70° S and 70° N at all longitudes. We analyze the cumulative size–frequency distribution (CSFD) and spatial distribution of these craters and find that in general the albedo-rayed population and the rocky population are consistent with an aggregate age of ∼1.2 Gyr, and both groups show deviations from the CSFD predicted by canonical production and chronology functions at diameters >30 km. Strikingly, we also find that although the rocky craters and craters with thermophysical rays show uniform spatial distributions with both longitude and latitude, the albedo-rayed craters show a strong equatorial concentration that deviates significantly from uniform and that is too large to be explained by analytical models of orbital motion.

“…The rims and slopes of these vents are rocky and have high thermal inertia (Figure 16), and are likely to obscure any potential low thermal inertia materials that could be blanketing portions of the top of the dome. Therefore, even if significant amounts of low thermal inertia materials accumulated in low-lying areas, the scattering and emission of infrared radiation from the surrounding slopes could significantly elevate the temperatures on the floor of the depression (Powell et al 2023). However, the evidence for fine-grained material is more obvious in the Mini-RF and Arecibo radar data, where we see relatively low CPR across the dome in the lower-lying regions that are less rocky and pitted (Figure 10).…”

Section: Cbvc Mons Hansteen and The Lassell Massif: Signatures Of Pyr...mentioning

confidence: 99%

Evidence for Fine-grained Material at Lunar Red Spots: Insights from Thermal Infrared and Radar Data Sets

Byron,

Elder,

Glotch

et al. 2023

Lunar red spots are small spectrally red features that have been proposed to be the result of non-mare volcanism. Studies have shown that a number of red spots are silicic, and are spectrally distinct from both highlands and mare compositions. In this work, we use data from LRO Diviner, Mini-RF, and Arecibo to investigate the material properties of 10 red spots. We create albedo maps using Diviner daytime solar reflectance data to use as an input to our improved thermophysical model, and calculate the rock abundance (RA) and H-parameter values that best fit Diviner nighttime thermal infrared radiance measurements. The H-parameter can be considered analogous to the thermal inertia of the regolith, with a high H-parameter corresponding to low thermal inertia. We find that the red spots generally have low RA, and do not have a uniform H-parameter but contain localized regions of high H-parameter. We additionally find that the red spots have a low circular polarization ratio (CPR) in many of the same locations that show a low RA and high H-parameter. Low RA, high H-parameter, and low CPR indicate a relative lack of rocks larger than ∼10 cm, which is consistent with previous findings of a mantling of fine-grained pyroclastic material for at least three red spots. Areas with high H-parameter but that do not show clear signs of pyroclastics in other data sets may be evidence of previously undiscovered pyroclastics, or could be due to the unique physical properties (e.g., porosity, rock strength/breakdown resistance) of the rocks that make up the red spots.