Physics
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p11a1579f&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #P11A-1579
Physics
[5430] Planetary Sciences: Solid Surface Planets / Interiors
Scientific paper
The terrestrial planets demonstrate a heavy bombardment of impacts in their early formation history. Impacts are violent, energetic collisions that may melt the surface and/or cause segregation of impactor material including silicates and liquid metal iron. Although theoretical studies have been done with conceptual models for metal diapir descent to form terrestrial planetary cores, physical or computer modeling studies are scarce due to the strong variations in physical properties between liquid metals and solid silicates. We use laboratory fluid experiments to study core formation processes using liquid metal gallium and high viscosity glucose syrup which provide the buoyancy ratios expected for planetary interiors and low Reynolds number flow dynamics. Preliminary results indicate that the physical process of sinking metal diapirs form trailing conduits that may drag low density surface magmatic material to the base of the mantle. The low density material collects, grows at the base of the box, and rises back to the surface. We compare two cases of a pond made of 1) liquid metal emulsion and 2) a smooth coalesced metal pond. We find that emulsion experiments entrain greater amounts of low density fluid to the base of the box. Once the metal diapir reaches the base, conduit material exhibits flow reversal to return buoyantly to the surface. In the case of coalesced liquid metal diapirs, low density conduit material returns to the surface through the pre-established conduit. In the emulsion diapir case, we observe the formation of a new thermo-chemical buoyant plume that grows, exits the conduit, and travels along a new pathway to the surface. Metal plume descent and chemical plume rise velocities are consistent with Stokes velocity. Estimates of metal-silicate plume sinking time and thermo-chemical plume rise time for terrestrial planetary interiors are provided. We suggest the observation of a thermo-chemical plume as a source for orogeny at the surface of terrestrial planets that may have produced the first mantle plumes and early volcanoes during core forming events.
Fleck Jean-Julien
Weeraratne Dayanthie S.
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