1. David Rothery, Dept of Earth & Environmental Sciences D.A.Rothery@open.ac.uk With thanks to the ESA Mercury Surface & Composition Working Group Spatial heterogeneity in Mercury’s surface

5. Simulations from Horner et al. (2006) The final embryo-embryo collision?

7. Primary & Secondary crust defined by Taylor, S. R. (1982, 1989)

9. Mixed crust types (if you don’t recognise the distinction!) oxideHighlands Low-Ti basalt High-Ti basalt Average basalt Average nearside Average globe Bulk Moon SiO 2 4544384144 47 TiO 2 0.562.6137.82.71.80.3 Al 2 O 3 24.67.878.88.419.721.86 FeO6.621.719.720.710.99.013 MgO6.814.98.411. 78.37.629 CaO15.88.310.79.513.914.74.5 Na 2 O0.450.230.360.290.400.420.09 K2OK2O0.030.05 0.0360.0330.01 Mn (ppm)57021502080211010308301200 Cr (ppm)800526030304140180013704200 Ni (pm)100642338089400 Primary crust (70% of nearside) Secondary crust (30% of nearside) Lunar crust examples

10. 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 for understanding Mercury’s origin.

11. BepiColombo MIXS elements

12. Secondary crust Primary crust? (probably not in this example) Mariner-10 PIA02443

13. Scale of variation within secondary crust (Caloris, MESSENGER) Older Younger Dark halo Fresh ejecta Deposit on floor of Sander crater