Can Mantle Potential Temperatures be Used to Infer the Tectonic Evolution of Terrestrial Planets?

Abstract:

A survey of geologic activity within the Solar System finds most planetary bodies to be currently operating within a stagnant-lid regime. However, Earth is an outlier and is the only body in the solar system for which we have direct observations of tectonic state. Venus, “Earth’s twin” has the potential to be another such outlier, with its broad similarity in size and bulk composition to the Earth, its current and past tectonic states are hotly debated [1-3]. However, Earth is currently the only body for which significant information about internal planetary processes is accessible, and for which direct estimates of internal temperatures of the mantle (mantle potential temperatures – T_P) can be estimated. While T_P estimates for other bodies have been made remotely [4,5], they tend to have high error, low sample size, and lack internal context. Recently it has been shown that the internal temperatures of 3D numerical simulations follow well prescribed scaling laws [6], and that specific lid states have specific predictions for temperatures [6], i.e., stagnant-lids have measurably greater temperatures than mobile-lids for the same parameter values. These results allow for T_P to be considered in a new context. Here we calculate T_P for Venus, Mars, Mercury, and the Earth using available geochemical data with well-established relationships between olivine composition and T_P, and use these constraints to infer the thermal-tectonic evolution of planets using the scaling laws derived from numerical simulations [4]. We show the remotely determined T_Pto be viable indicators of lid-state, and offer the first quantitative and data driven determination of tectonic states through the inner Solar System. Implications for the evolution of Mercury, Mars, Venus, and Earth will be discussed.

[1] Schubert et al. (1997) Univ. Arizona Press; [2] Turcotte (1993) JGR; [3] Kiefer (2013) LPSC; [4] Lee et al. (2009) EPSL; [5] Filliberto and Dasgupta (2015) JGR; [6] Weller et al. (2014) AGU fall meeting.