Crustal recycling, mantle dehydration, and the thermal evolution of Mars

Abstract

Please cite this article as: Morschhauser, A., Grott, M., Breuer, D., Crustal recycling, mantle dehydration, and the thermal evolution of Mars, Icarus (2010), doi: 10.1016/j.icarus.2010 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Crustal recycling, mantle dehydration, and the thermal evolution of Mars Mars would then be driven by the extraction of a primordial crust after core formation, cooling the mantle to temperatures close to the peridotite solidus. According to this scenario, the second stage of global crust formation took place over a more extended period of time, waning at around 3500 Myr b.p., and was driven by heat produced by the decay of radioactive elements. Present-day volcanism would then be driven by mantle plumes originating at the core-mantle boundary under regions of locally thickened, thermally insulating crust. Water extraction from the mantle was found to be 1 relatively efficient and close to 40 percent of the total inventory was lost from the mantle in most models. Assuming an initial mantle water content of 100 ppm and that 10% of the extracted water is supplied to the surface, this amount is equivalent to a 15 m thick global surface layer, suggesting that volcanic outgassing of H 2 O could have significantly influenced the early Martian climate and increased the planet's habitability.

The habitability of a stagnant-lid Earth

“…5a, the thermal history is generally characterized by an initial heating phase during which convective cooling is not efficient enough to remove the internal heat generated by the decay of radioactive elements, a behaviour that is characteristic of the early evolution of the interior of stagnantlid bodies (e.g. Morschhauser et al 2011;Tosi et al 2013). After this phase, which lasts between 500 and 1500 Myr depending on the model parameters, the mantle and the core (not shown) cool at a roughly constant rate of ∼ 40 K/Gyr.…”

“…5c) stops growing when it becomes as thick as the stagnant lid; there is a sharp bend in the crust curves when they cross the stagnant-lid curves indicated with dashed lines. When this happens, the erosion of the bottom part of the crust starts (Morschhauser et al 2011) and continues until the rate at which the stagnant lid thickens because of mantle cooling overcomes the rate at which crust is produced. In our reference model, this phase lasts between ∼ 800 and 3300 Myr (thick black lines in Fig.…”

Mars: a small terrestrial planet

“…This leaves us with two possible alternatives: a thick (>100 km) and non-porous basaltic crust, or a thin (∼50 km) stratified crust with a non-basaltic and/or porous component (Nimmo and Tanaka 2005;Baratoux et al 2014). The present-day average crustal thickness is poorly constrained by numerical simulations, with values ranging from several tens of kilometers to more than 100 km, depending on hypotheses made on the heat budget, water content, and mantle rheology (Hauck and Phillips 2002;Breuer and Spohn 2006;Fraeman and Korenaga 2010;Morschhauser et al 2011). A thick basaltic crust could also match with the moment of inertia factor (Baratoux et al 2014).…”

“…Formation and early evolution of the crust likely involve significant degassing of the martian mantle (Jaskosky and Jones 1997; Filiberto et al 2016). In the absence of a mechanism for replenishment of the mantle in volatile species, it is usually considered that the present-day mantle is essentially dry, though even minor volatile concentration may have important consequences on the subsequent evolution (e.g., mantle rheology is sensitive to water levels at the level of ∼100 ppm, Morschhauser et al 2011) …”

“…The volatile concentrations of the mantle source and the volume of magma reaching the surface (effusion rate) determine the amount of volatile species that have been released in the atmosphere as a function of time. In the absence of plate tectonics, the convecting mantle below the stagnant lid depletes continuously with time, as there is no mechanism to replenish the mantle with volatiles (Morschhauser et al 2011). Intense degassing likely took place during the formation and crystallization of the magma ocean.…”