Geological Processes on Mercury and the Mapping of the Derain (H-10) Quadrangle.

Malliband, Christopher Charles (2021). Geological Processes on Mercury and the Mapping of the Derain (H-10) Quadrangle. PhD thesis The Open University.

Abstract

I present the results from the first geological map of the Derain (H-10) quadrangle of Mercury and in-depth studies of features identified in the map.

I used ArcGIS software to produce the geological map by integrating and analysing data from the MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft. My results show that the Derain quadrangle has a similar geological history to other quadrangles investigated on Mercury. My mapping showed that two plains classifications are insufficient to represent the diversity of plains material within the Derain quadrangle. Intermediate plains remain enigmatic, but I conclude that at least some are likely to be thin coverings of lava, insufficient to hide underlying craters, that are younger than most smooth plains.

My work to characterise plains units within the Derain quadrangle led to an investigation of previously unstudied small patches (<15,000 km²) of smooth plains, both within and outside the Derain quadrangle. Several of these are found abutting (ponded against) lobate scarps. Therefore, these smooth patches must post-date the onset of global contraction and so the end of widespread effusive volcanism. The mechanism of emplacement is not clear, but smooth patches are most likely formed by either late-stage volcanism or impact-related processes. In most cases, I argue for a volcanic origin.

While investigating the Derain quadrangle, I identified a previously unknown mass-wasting process on Mercury: down-slope streaks that I refer to as ‘slope lineae’. I surveyed the Hokusai quadrangle for these features and show that slope lineae are found predominantly on equator-facing slopes. The preference for equator-facing slopes, common association with ‘hollows’, and the morphology of some examples may indicate that volatile loss contributes to their formation.

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