When NASA’s Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander touches down on Mars in November 2018, it will become the planet’s most advanced geophysical monitoring station. From its landing site on the plains of Elysium Planitia, the craft will attempt to probe the inner depths of the planet with its suite of instruments.
InSight’s goal is to reconstruct how rocky planets like Mars — and Earth — form. One of its most important objectives (to be performed with the Heat Flow and Physical Properties Probe developed at the German Aerospace Center) will be measuring how much heat rises from the planet’s mantle to the surface. This heat, produced by the decay of radiogenic elements, has been building and escaping to the surface since Mars was forged in the early solar system. Knowing the planet’s global average heat flux will help scientists determine the composition and structure of its interior and constrain different models of planet formation.
But to make a truly global measurement, InSight will need some help. It’s not a rover: It will remain stationary, and thus, its heat flux readings will be heavily biased if, for example, it happens to land atop an enormous mantle plume stretching out below the Elysium Mons volcano, roughly 1500 kilometers to the north. To generalize its findings to the rest of the planet, scientists must rely on computer models that simulate how heat flows up through the mantle and crust to the surface.
To that end, Plesa et al. [in the Journal of Geophysical Research] have produced the most detailed simulations to date. They’re the first to use 3-D thermal evolution models with crustal thickness changes across the planet based on gravity and topographical data. These models are combined with an inference of residual radioactivity in the rock of the crust, which also emits heat that makes its way to the surface. Such residual radioactivity wouldn’t be unprecedented: Patches of radioactivity near the Apollo 15 landing site caused surface heat flux readings to be an estimated 2–4 times higher than elsewhere on the Moon. [More at links]