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Abstract The apparent end of the internally generated Martian magnetic field at 3.6–4.1 Ga is a key event in Martian history and has been linked to insufficient core cooling. We investigate the thermal and magnetic evolution of the Martian core and mantle using parameterized models and considered three improvements on previous studies. First, our models account for thermal stratification in the core. Second, the models are constrained by estimates for the present‐day areotherm. Third, we consider core thermal conductivity,, values in the range 5–40 Was suggested by recent experiments on iron alloys at Mars core conditions. The majority of our models indicate that the core of Mars is fully conductive at present with core temperatures greater than 1940 K. All of our models are consistent with the range ofW. Models with an activation volume of 6 (0)require a mantle reference viscosity of Pa s.
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Reference Models for Lithospheric Geoneutrino Signal
Abstract Debate continues on the amount and distribution of radioactive heat producing elements (i.e., U, Th, and K) in the Earth, with estimates for mantle heat production varying by an order of magnitude. Constraints on the bulk‐silicate Earth's (BSE) radiogenic power also places constraints on overall BSE composition. Geoneutrino detection is a direct measure of the Earth's decay rate of Th and U. The geoneutrino signal has contributions from the local (40%) and global (35%) continental lithosphere and the underlying inaccessible mantle (25%). Geophysical models are combined with geochemical data sets to predict the geoneutrino signal at current and future geoneutrino detectors. We propagated uncertainties, both chemical and physical, through Monte Carlo methods. Estimated total signal uncertainties are on the order of20%, proportionally with geophysical and geochemical inputs contributing30% and70%, respectively. We find that estimated signals, calculated using CRUST2.0, CRUST1.0, and LITHO1.0, are within physical uncertainty of each other, suggesting that the choice of underlying geophysical model will not change results significantly, but will shift the central value by up to15%. Similarly, we see no significant difference between calculated layer abundances and bulk crustal heat production when using these geophysical models. The bulk crustal heat production is calculated as 7 2 TW, which includes an increase of 1 TW in uncertainty relative to previous studies. Combination of our predicted lithospheric signal with measured signals yield an estimated BSE heat production of 21.5 10.4 TW. Future improvements, including uncertainty attribution and near‐field modeling, are discussed.
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- Award ID(s):
- 1650365
- PAR ID:
- 10456246
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Solid Earth
- Volume:
- 125
- Issue:
- 2
- ISSN:
- 2169-9313
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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