DI51A-4351:
Mars Thermal History: Core, Atmosphere, Mantle, Phobos and Surface (MaTH CAMPS)

Friday, 19 December 2014
June K Wicks1, Matt B Weller2, Nathan J Towles3, Christopher Thissen4, Nicholas R Knezek5, Stephanie Johnston6, Sutatcha Hongsresawat7, Megan S Duncan2, Benjamin A Black8, Nicholas C Schmerr6, Mark P Panning9, Laurent Montesi10, Michael Manga11 and Philippe Henri Lognonne12, (1)Princeton University, Princeton, NJ, United States, (2)Rice University, Houston, TX, United States, (3)Johns Hopkins Univ, Baltimore, MD, United States, (4)Yale Univ-Geology & Geophysics, New Haven, CT, United States, (5)University of California, Berkeley, CA, United States, (6)University of Maryland College Park, College Park, MD, United States, (7)University of Florida, Gainesville, FL, United States, (8)University of California Berkeley, Berkeley, CA, United States, (9)Univ of FL-Geological Sciences, Gainesville, FL, United States, (10)University of Maryland, College Park, MD, United States, (11)Univ of California Berkeley, Berkeley, CA, United States, (12)Institut de Physique du Globe de Paris, Paris, France
Abstract:
The death of the Martian dynamo ~4.1 Ga and sustained volcanism throughout Martian history place fundamental constraints on the thermal history of the planet. To explore the implications for mantle structure, we constructed holistic models of Mars that include the core, mantle, lithosphere/surface, atmosphere, and an atmospheric capture of Phobos in a collaborative effort begun at the CIDER 2014 summer program.

For our thermal model of the core, we employ an iterative solver and parameterized phase diagram to compute pressure, density, and temperature in the core for a variety of initial accretion temperatures and bulk compositions. We use this model to constrain core-mantle boundary (CMB) temperature and heat flow.

We couple this model for the evolution of the core with a one-dimensional parameterized convection model for the mantle. The upper boundary condition is set by the state of the Martian atmosphere. We consider the effect of a distinct compositional layer at the base of the mantle that may represent dense magma ocean crystallization products or a primitive layer untouched by magma ocean processes. We find successful models that allow sufficient CMB heat flow to power an early dynamo and the potential of melt generation through extended periods of Mars’ history.

In addition to dynamo and magmatism timing, other diagnostics allow us to compare model outputs to modern observables. The mass, moment of inertia, and tidal Love number of our model planet are compared directly to measured values. Additionally, deformation and stress on the lithosphere due to internal volume changes and changes in surface loading predicted by our thermal evolution models could be recorded in the Martian crust. Finally, coupling temperature-dependent tidal dissipation affects Phobos’ orbital secular evolution and gives constraint on mantle temperatures. These constraints are discussed for the different scenarios of Phobos capture.

We present a suite of models that satisfy the constraints of mass, moment of inertia, dynamo power and shutoff timing in addition to outlining predictions and implications for the forthcoming InSight and MAVEN missions.

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