Spatial heterogeneityin Mercury’s surface David Rothery, Dept of Earth & Environmental Sciences D.A.Rothery@open.ac.uk With thanks to the ESA Mercury Surface & Composition Working Group
The final embryo-embryo collision? Simulations from Horner et al. (2006)
Primary & Secondary crust defined by Taylor, S. R. (1982, 1989)
Lunar crust examples Primary crust (70% of nearside) Secondary crust (30% of nearside) Mixed crust types(if you don’t recognise the distinction!)
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.
Primary crust?(probably not in this example) Secondary crust < 350 km > Mariner-10 PIA02443
Scale of variation within secondary crust(Caloris, MESSENGER) Fresh ejecta Older Younger Deposit on floor of Sander crater Dark halo < 40 km >