Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 – 23 September 2022
Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 September – 23 September 2022

TP3

Forward to the Moon: The Science of Exploration

Human and robotic lunar exploration is opening new vistas and scientific understanding as humanity reaches toward the Moon again. In partnership with institutions around the globe, the Solar System Exploration Research Virtual Institute (SSERVI) focuses on these scientific aspects of exploration as they relate to the Moon and other airless bodies. This session will feature interdisciplinary, exploration-related science centered around the Moon as a human and robotic destination. Scientific plans and results within this session represent the broad spectrum of lunar science representing investigations of the Moon and its environment as a planetary body as well as science research uniquely enabled by being done from the Moon. Graduate students and early career researchers are particularly encouraged to submit for oral presentations.

Co-organized by MITM
Convener: Gregory Schmidt | Co-conveners: Mahesh Anand, Kristina Gibbs, Brian Day
Orals
| Wed, 21 Sep, 12:00–13:30 (CEST), 15:30–18:30 (CEST)|Room Manuel de Falla
Posters
| Attendance Mon, 19 Sep, 18:45–20:15 (CEST)|Poster area Level 1

Orals: Wed, 21 Sep | Room Manuel de Falla

Chairpersons: Kristina Gibbs, Gregory Schmidt, Brian Day
12:00–12:10
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EPSC2022-97
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ECP
Shreekumari Patel, Animireddi V Satyakumar, and Mohamed Ramy El-maarry

Introduction: Floor-Fractured Craters (FFCs) are unique lunar landforms that have witnessed and recorded tectonic and volcanic activity in the form of distinct structural features [1]. FFCs are common around the edges of mare basins, and their ages span the lunar history [2,3]. They offer insights into the region’s magmatic, thermal and morphological evolution and are candidates for further investigation to comprehend the Moon’s crustal evolution. Therefore, the detailed analysis of FFCs would give new insights into a better understanding of the volcanic activity on the Moon. In connection with this, we selected a Posidonius crater on the nearside of the Moon to perform detailed geological and geophysical analysis to understand the volcanic history.

The Posidonius crater is ~95 km in diameter and is categorised as a Class-III Floor-Fractured crater located on the northeastern rim of the Serenitatis basin [4], with a center latitude and longitude of  31.88°N and 29.99°E as shown in Figure 1. The wide annular depression called moat is noted on the western side of the crater nearest to the exterior Mare Serenitatis plain. The mare infill is divided into two basaltic units by ~180 km long, curvy lava channel known as Rimae Posidonius. The existence of large and small-scale graben and sinuous rille and basaltic infill indicate that tectonic, as well as volcanic processes, deformed the Posidonius crater.

Data and Methodology: The gravity data from Gravity Recovery and Interior Laboratory (GRAIL) of degree and order 660 was used to map the gravity anomalies. The global lunar crustal thickness model-1 was used to see the crustal thickness variations. The composition of the crater and eastern part of Mare Serenitatis was derived using Moon Mineralogy Mapper (M3) onboard the Chandrayaan-1 mission [5]. Band parameters were calculated for mapping first-order mineralogical variation [6]. LRO (Lunar Reconnaissance Orbiter) Mini-RF S-band data was processed to derive CPR and daughter products [7] for the physical characterisation of the study region [8]. LRO NAC (Narrow-Angle Camera) of spatial resolution ~0.5-2 meters/pixel [9] was used to identify and map the structural features.

 

Results and Discussion:

The gravity anomalies ranged from -413 to 558 mGal (Figure 2A), with high values observed at the outer rim of the Serenitatis basin and low values found at the east, south-east of the Posidonius crater. These anomalies show the decreasing trend towards the northern part of Posidonius crater, indicating that the possible source of volcanic history is the Serenitatis basin. The crustal thickness (Figure 2B) shows low at Serenitatis and Posidonius crater, which suggests the volcanic source is shallow level. Minerals were identified using VNIR spectral characteristics. The crater exhibits exposures of mafic minerals detected from Rimae Posidonius, Floor-Fractures, central peak ring, and mare unit (Figure 3A). Pyroxene spectral shows absorption near 1000 nm and 2000 nm due to Fe2+ and Ca2+ contribution [10]. M3 data suggests that the mare unit is dominated by the subcalcic ferroaugite to Ferroaugite rich rocks such as basalt (Figure 3B and 3C). Spectra of bedrock exposures from rimae and ridge show the presence of magnesium-pigeonite, which suggests the rapid cooling of magma at high temperature. Hence, the enigmatic rimae Posidonius represent the shallow lava flow resulting from a turbulent flow of low-viscosity, high-temperature, rapid cooling lava that erodes the pre-existing mare deposits in Posidonius crater.

Mini-RF Circular Ratio Polarisation (CPR) and m-chi decomposition map of crater display the radar-bright characteristics of tectonic features and small-sized fresh craters. The Posidonius crater exhibits low-CPR values suggesting the maturity scale of the crater. Still, the central peak ring, rimae Posidonius, floor fracture, and small-sized fresh crater show high CPR values due to boulder fields in the vicinity. High-CPR value region represents the mixed scattering of double bounce and volumetric scattering (yellowish hue) as they expose fresh and/or dihedral geometrical surface concentrated at the base or in the vicinity of peak ring, linear/sinuous features, and secondary craters (Figure 4).

Conclusions:

The geological (M3, Mini-RF, and NAC analysis) and geophysical (gravity, crustal thickness) observations in this area revealed extensive eruptions during formation and after formation. It is also observed that the lithospheric loading of the Serenitatis basin influences the origin and modifications of this crater. The detailed analysis and mapping of this region are under process.

 

Acknowledgements

SP and MRELM acknowledge support for this work through an internal grant (8474000336-KU-SPSC). AVSK is thankful to the director, CSIR-NGRI, Hyderabad, for all the support.

References:

[1] Chauhan, M. et al. (2021) Lunar and Planetary Science Conference (LPSC) 2548, 1843.

[2] Jozwiak, L. M. et al. (2012) JGR:Planets 117(E11).

[3] Jozwiak, L. M. et al. (2015) Icarus 248, 424-227.

[4] Salem, I. B. et al. (2022) Remote Sensing 14(4), 814.

[5] Pieters, C. M. et al. (2009) Current Science, 500-505.

[6] Purohit, A. N. et al. (2021) Journal of Earth System Science 130(1), 1-23.

[7] Raney, R. K. et al. (2012) JGR: Planets 117(E00H21), 1-8.

[8] Patel, S. M. and Solanki, P. M. (2018) Proceedings ACRS, TS70.

[9] Robinson, M. S. et al. (2010) Space Science reviews 150, 81-124.

[10] Klima, R. L. et al. (2011) Meteorite and Planetary Science 46, 379-395.

How to cite: Patel, S., Satyakumar, A. V., and El-maarry, M. R.: Extensive volcanic activity within the Posidonius crater, nearside of the Moon, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-97, https://doi.org/10.5194/epsc2022-97, 2022.

12:10–12:20
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EPSC2022-280
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ECP
Hannes Bernhardt, Jaclyn D. Clark, and Mark. S. Robinson

Introduction: The Aristarchus Plateau is a unique region on the Moon, hosting its highest concentration of rilles including the widest and deepest rille [1], its most extensive dark mantle deposits [2], as well as rare exposures of both, very olivine-rich and very silicate-rich materials [3–6]. As such, the plateau has been considered as one of the most promising exploration sites apart from the lunar poles for decades [7–10]. To facilitate future in-situ operations and devise traverse plans on the plateau, we are mapping a 285 km2 area centered at 50.53°E 24.51°N, which includes crater Herodotus G, ~27 km northwest of the rim of crater Herodotus (Fig. 1, black outline). For context, and as there exists no dedicated, peer-reviewed map of the Aristarchus Plateau, we are producing a regional map (~103 km2) centered at 50.75°E 26.11°N, encompassing the entire plateau and the Montes Agricola. Here we present a progress report on this regional map (Fig. 1).

Data: A 7 m/pixel mosaic of SELENE (“Kaguya”) Terrain Camera (TC) morning images, i.e., with homogeneous illumination from the east [11] serves as our map base. We also utilize several other datasets (for explanation of abbreviations see references): LOLA-Kaguya (merged topography and derivatives [12]); LROC-WAC (high and low incidence [13]), Clementine (NIR and UV-VIS mosaics [14]); Diviner (rock abundance, CF position, and temperature [15]); Arecibo-Green Bank radar (S-band circular polarization, [16]). Pre-Kaguya/LRO maps including the Aristarchus plateau are also consulted for reference and regional context [17–19].

For our local mapping (Fig. 1, black rectangle), we will also consult three LROC-NAC mosaics (two opposing high incidence and one low incidence [13]) as well as NAC-derived stereo topography [20,21].

Methodology: Regional mapping is carried out at a scale of 1:80,000. Initial identification and digitization of linework and units is conducted on our basemap (Kaguya TC) in conjunction with merged LOLA-Kaguya data (topography, hillshade, and slopemap). Further unit characterization and delimitation is based on all datasets listed in the Data section.

Our regional mapping approach is similar to the composite map by [18]. However, we will map mineralogic units that lack corresponding morphologic or albedo signatures (e.g., olivine-rich areas on the southeastern rim of Aristarchus [3,4] or silicic areas in several specific locations [5,6]) as overlay textures instead of assigning separate units. For our local map we plan a mapping scale of 1:15,000 using LROC-NAC mosaics at different incidence angles as basemaps.

Initial results: We identified 45 potential volcanic collapse structures (irregular pits; IRPs; Fig. 1, red units) ranging in areal extent from ~0.3 km2 to ~110 km2 with a mean at ~7 km2. Most of these structures have not been reported in previous investigations and all but six IRPs are located on the Aristarchus plateau. IRPs were defined as depressions fulfilling at least three of the following criteria: 1) Irregular shape; 2) Anomalous depth-diameter-ratio; 3) Not surrounded by spectral signatures consistent with impact ejecta; 4) Connected to or closely associated with a rille or with a partially breached rim.

In our map, the term “rille” is defined as linear depression indicating a formation by volcanic drainage, i.e., it has to fulfill two of the following criteria: 1) Sinuous trace; 2) Following the topographic gradient; 3) Connected to or closely associated with an IRP. We mapped a total of 100 rilles with total, maximum, and minimum lengths of 1724 km, 110 km, and 0.5 km, respectively. Additionally, we identified 78 highly degraded rilles and segments, for a total rille length of ~2033 km. This includes at least 37 rilles and rille segments that have not been identified in previous investigations [1,18]. We also detected two ~3.7 km long and up to ~24 m high, sinuous ridge segments approaching Rima Krieger. Two more ~2.5 km and ~5 km long sinuous ridges are located north of the Montes Agricola. If these represent inverted rilles, they would triple the number of such features identified on the Moon [1].