Geology of the Raditladi quadrangle, Mercury (H04)

Abstract

In this work, we present a 1:3,000,000-scale geologic map of the Raditladi quadrangle (H04) of Mercury. The area covers nearly 7% of the entire planet and encompasses several features of interest such as the Caloris basin, the Raditladi basin, hollow clusters and volcanic features. The mapping took advantage of the data produced during MESSENGER's orbital phase. The mapped deposits include impact-related units observed at several scales from the Caloris basin to the secondary crater chains. The Smooth Plains unit covers the majority of the area, mantling the older Intercrater Plains and Bright Intercrater Plains units. Results show that the emplacement of all the main units and the Caloris impact event, representing the main geologic events in the quadrangle, were concentrated between 3.96 and 3.72 Ga. After this intense phase, the geologic framework was modified only by local events such as impact craters and hollow formation. This map is among the first products for the detailed geologic characterization of Mercury at such a scale. It will contribute as a constraint and a support for both further local investigation and mapping, and targeting of the forthcoming BepiColombo ESA/JAXA joint exploration mission to Mercury. ARTICLE HISTORY

Mercury's Caloris basin: Continuity between the interior and exterior plains

“…The simplest explanation (bearing in mind that crater counting has not been able to separate them) is that emplacement of interior and exterior plains occurred during an overlapping time period and that they were erupted from multiple sources suggesting flow lengths of the order of hundreds but not thousands of kilometers. This is consistent with crater counts, given the errors and limitations of the various methods [ Denevi et al ., ; Fassett et al ., ; Mancinelli et al ., ]. The Caloris interior plains have an estimated volume [ Ernst et al ., ] of 3.2–5.2 × 10 6 km 3 , and to this we must add a probably similar volume to account for the exterior plains, suggesting that the order of 1 × 10 7 km 3 of lava was emplaced in a single epoch.…”

“…This location falls within the 1:3 M quadrangle geologic map of Mancinelli et al . [], from which Figure is an extract.…”

“…Location 4, exactly the same area as in Figure , showing the mapping of Mancinelli et al . []. “Caloris smooth plains” correspond to our interior plains, and smooth plains correspond to our exterior plains.…”

“…We defined training areas on interior red plains, exterior blue plains, and (to avoid inappropriately forcing all pixels into one or other of the plains units) also bright crater ejecta and “low‐reflectance material.” The example of our results shown in Figure confirms that the Mancinelli et al . [] morphotectonic feature bears no relation to any spectral boundary and that the exterior blue plains do indeed include patches of redder material. Because the color edges are diffuse, varying the parameters of the classification routine causes the line bounding interior and exterior units to migrate east or west and the patches to grow or shrink or to change in number.…”

“…Interior plains pass through this and merge imperceptibly into a smooth facies draped over rim material (mapped as Caloris Rough Ejecta by Mancinelli et al . [] and as Nervo Formation by Goosmann et al . []).…”