Lunar Thermo-Chemical Evolution
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Transcript of Lunar Thermo-Chemical Evolution
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Asymmetric evolution of the Moon
M. Laneuville (IPG, Paris), M.A. Wieczorek (IPG, Paris), D. Breuer (DLR, Berlin) and N. Tosi (DLR/TU, Berlin)
or how to melt the nearside...
44th LPSC18-22 March, 2013
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magmatic asymmetry
Motivation
LRO/WAC
NEARSIDE FARSIDE
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compositional asymmetryLP/GRS/Mimoun et al., 2011
NEARSIDE FARSIDE
0 2 4 6 8 10 12Thorium (ppm)
Motivation
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Observation
1. 99% of volcanism occured on the nearside (~107 km3)
2. Nearside volcanism stopped ~1 Ga ago
3. Sporadic farside volcanism occur until ~3 Ga ago
Constraints
✓ strong heat sources enrichment on the nearside
What do successful models predict?
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➡ Initial temperature profile follows magma ocean crystallization
➡ The heat sources are already localized below the PKT
• 2D conduction model (Wieczorek & Phillips, 2000; Hess and Parmentier, 2001)
• 3D thermo-chemical evolution code GAIA (DLR)
• assume rheologie
• assume initial conditions
Method
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Model: initial temperature profile
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Model: initial heat source distribution
3 possible distribution:- below the crust- at the bottom of the crust- within the crust
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Results: cold start, KREEP below the crust
not enoughvolcanism!
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Results: hot start, KREEP below the crust
too muchvolcanism!
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Results: intermediate start, KREEP below the crust
successful!1. NS melt volume2. NS melt duration3. FS melt volume4. FS melt duration
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Results: predicted gravitational signature
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result: total gravity signature estimate
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- heating the nearside mantle actually increases the heat flow
- it may help having a long lasting chemical dynamo
Results: CMB heat flow evolution and magnetic field
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Conclusion & take home messages
1. lunar volcanism can be explained by heat sources enrichment in the PKT
2. it predicts a present temperature anomaly
- Laneuville et al. (2013), submitted to J. Geophys. Res.
3. it influences core evolution
- work in progress