Geology of the Bach quadrangle (H15), mercury

Mercury’s Bach quadrangle (H15) is the areapoleward of 65 °S. We mapped this geologically using remote sensing-basedobservations of surface morphology revealed on MESSENGER data products. Thismap contributes to a series of quadrangle maps providing geological context forthe ESA-JAXA BepiColombo mission to Mercury. We performed digitisation at ∼1:400,000scale and final publication scale is 1:3,000,000. There are four morphologicallydistinct plains units: intercrater, intermediate, smooth, and very smooth.Impact craters cover much of H15’s surface. Following convention, we mappedcrater materials for all craters ≥20 km, classifying them on the basis ofmorphological evidence for degradation. We produced two map versions, using athree-class and a five-class crater degradation scheme. We include twogeological aspects that have not featured in previous maps of the series, bymapping occurrences of lobate ejecta at craters ≥20 km and depicting thedistribution of the south polar permanently shadowed regions.