Spatial heterogeneity in Mercury’s surface
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Transcript of Spatial heterogeneity in Mercury’s surface
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David Rothery, Dept of Earth & Environmental [email protected] thanks to the ESA Mercury Surface & Composition Working Group
Spatial heterogeneityin Mercury’s surface
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Simulations from Horner et al. (2006)
The final embryo-embryo collision?
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Primary & Secondary crust defined by Taylor, S. R. (1982, 1989)
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Mixed crust types(if you don’t recognise the distinction!)
oxide HighlandsLow-Ti basalt
High-Ti basalt
Average basalt
Average nearside
Average globe
Bulk Moon
SiO2 45 44 38 41 44 44 47TiO2 0.56 2.6 13 7.8 2.7 1.8 0.3Al2O3 24.6 7.87 8.8 8.4 19.7 21.8 6
FeO 6.6 21.7 19.7 20.7 10.9 9.0 13
MgO 6.8 14.9 8.4 11. 7 8.3 7.6 29
CaO 15.8 8.3 10.7 9.5 13.9 14.7 4.5Na2O 0.45 0.23 0.36 0.29 0.40 0.42 0.09K2O 0.03 0.05 0.05 0.05 0.036 0.033 0.01
Mn (ppm) 570 2150 2080 2110 1030 830 1200
Cr (ppm) 800 5260 3030 4140 1800 1370 4200
Ni (pm) 100 64 2 33 80 89 400
Primary crust(70% of nearside)
Secondary crust(30% of nearside)
Lunar crust examples
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We cannot back-track from crust composition to mantle composition unless we:• recognise how the crust formed• measure and model primary crust and secondary crust separately
Mantle composition is essential forunderstanding Mercury’s origin.
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BepiColombo MIXS elements
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Secondary crust
Primary crust?(probably not in this example)
Mariner-10 PIA02443< 350 km >
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< 40 km >
Scale of variation within secondary crust(Caloris, MESSENGER)
OlderYounger
Dark halo
Fresh ejecta
Deposit onfloor of Sandercrater
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