Abstract
AbstractThe duration and timing of volcanic activity on Mercury are key indicators of the thermal evolution of the planet and provide a valuable comparative example for other terrestrial bodies. The majority of effusive volcanism on Mercury appears to have occurred early in the planet's geological history (~4.1–3.55 Ga), but there is also evidence for explosive volcanism. Here we present evidence that explosive volcanism occurred from at least 3.9 Ga until less than a billion years ago and so was substantially more long‐lived than large‐scale lava plains formation. This indicates that thermal conditions within Mercury have allowed partial melting of silicates through the majority of its geological history and that the overall duration of volcanism on Mercury is similar to that of the Moon despite the different physical structure, geological history, and composition of the two bodies.
Highlights
In order to constrain models for the composition, internal structure, and formation history of Mercury, it is necessary to assess the duration of volcanism
Explosive vents within the Caloris basin clearly superpose the effusively emplaced Caloris interior lava plains [Head et al, 2009; Rothery et al, 2014], and it has been suggested that some explosive volcanism on Mercury in general may have occurred in the Mansurian Period (3.5–1 Ga) [Goudge et al, 2014], which indicates that this type of volcanic activity is a potential indicator of the true duration of volcanic activity
We explored the effect of using a different crater production function to assess the surface age by comparing these model ages with those indicated by the Model Production Function (MPF) of Marchi et al [2009] at one location
Summary
In order to constrain models for the composition, internal structure, and formation history of Mercury, it is necessary to assess the duration of volcanism. On the basis of the anomalous spectral characteristics and diffuse margins of these deposits, plus the apparently endogenic nature of the pits, these are widely accepted as pyroclastic deposits formed by explosive volcanism [e.g., Grott et al, 2011; Byrne et al, 2013]. This style of volcanism occurs through separation of volatiles from rising magma, so its occurrence challenges formation models for Mercury predicting a volatile-depleted bulk composition [Cameron, 1985; Fegley and Cameron, 1987; Wetherill, 1988; Benz et al, 2007]. Explosive vents within the Caloris basin clearly superpose the effusively emplaced Caloris interior lava plains [Head et al, 2009; Rothery et al, 2014], and it has been suggested that some explosive volcanism on Mercury in general may have occurred in the Mansurian Period (3.5–1 Ga) [Goudge et al, 2014], which indicates that this type of volcanic activity is a potential indicator of the true duration of volcanic activity
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