Mapping Mercury’s Debussy Quadrangle and Exploration of Volcanic Vents on a Shrinking World

Pegg, David Lawrence (2021). Mapping Mercury’s Debussy Quadrangle and Exploration of Volcanic Vents on a Shrinking World. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.00012e63

Abstract

NASA’s MESSENGER (Bacronym: MErcury Surface, Space Environment and Ranging) spacecraft was the first to orbit the planet Mercury and return images of the entire globe. This thesis uses data from this mission to build a better understanding of the planet, its volcanic, and tectonic nature.

I used image data to produce a 1:3 million scale geomorphological map of the H-14 “Debussy” Quadrangle, dividing the surface into crater materials and three generations of volcanic plains. I classified craters using two different morphological (degradation class) systems; a three-class and a five-class. I found the five-class system more useful. The Rembrandt impact basin and tectonic activity have also modified parts of this quadrangle.

Following on from mapping several explosive volcanic vents within the quadrangle, I undertook a global survey of volcanic vent sites to work out how many are compound volcanoes (comprised of multiple vents, and likely to have erupted multiple times). I found 71% of the vent sites with good image quality on Mercury are compound. Their repeated eruption requires either a continued supply of volatile-rich magma or assimilation of volatiles in the crust.

During my global vent survey, I identified a vent site that had exposed a fault scarp. This is the first direct observation of a fault scarp in three dimensions, and using shadow measurements, I measured the dip of the fault plane as 28° ±5°; this is within the range of those measured indirectly. If further measurements confirm this, then this would suggest that the higher end of estimates for Mercury’s global contraction (caused by cooling) are probably correct.

Volcanism on Mercury has shaped the planet’s surface and reflects its interior. Vent sites will be important targets for the BepiColombo mission, which launched during my research and is due to arrive in orbit around Mercury in 2025.

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