Mars rheology and thermal history revealed by the orbital evolution of its satellite Phobos
Unlike its surface, which we now know relatively well, details of Mars' internal structure and evolution are still poorly understood. Evidence of recent volcanic activity suggests that the deep interior of the Red Planet remains hot and is cooling through convection.
Publication date: 23/05/2019
Press, Research
Related teams :
Planetology and Space Sciences
Related themes : Earth and Planetary Interiors
Its cooling rate is linked to its initial thermal state and its rheology, which determines its capacity to deform and evolve dynamically. The study of the thermal evolution of Mars, combined with the available observations, makes it possible to reconstruct its dynamic history and current structure. However, such an approach is limited by the interdependence of several weakly constrained key quantities (such as temperature, composition and rheology).
A team of researchers from the Institut de Physique du Globe de Paris and the Jet Propulsion Laboratory reveal, in an article published in the journal Nature, that it is possible to gain a better understanding of the thermal history and rheology of Mars by considering its closest satellite, Phobos, whose orbital evolution is governed by the thermochemical history of the Red Planet, through tidal interactions.
By exploiting these relationships, the scientists found that Mars was originally slightly warmer than today (100 to 200 K) and that its mantle deformed slowly under the dislocation creep regime. This corresponds to a reference viscosity of 1022.2 ± 0.5 Pa s and an intrinsic viscosity sensitivity to moderate to relatively low temperature (activation energy of 280 ± 80 kJ/mol) and pressure (activation volume <14 cm3/mol). Their approach predicts an average Martian crust thickness of 40 ± 25 km and a surface heat flux of 20 ± 1 mW/m2. Comparison of these predictions with future data could reduce these thermal and rheological uncertainties.
Ref : H. Samuel, P. Lognonné, M. Panning & V. Lainey, The rheology and thermal history of Mars revealed by the orbital evolution of Phobos, Nature 569, 523-527 (2019), doi: 10.1038/s41586-019-1202-7
