Extending the Solidus for a Model Iron-Rich Martian Mantle Composition to 25 GPa

The solidus for the mantle of Mars is an important geophysical parameter in modeling the thermal history and evolution of the planet. This study provides solidus data for a simplified model Martian mantle composition from the midmantle (8 GPa) to the core-mantle boundary (25 GPa) using multianvil experiments. Combining this work with previous studies, the solidus for the entire mantle of Mars is constrained to within 70 degrees C. The major mineral assemblages and phase transitions observed are consistent with those predicted for an iron-rich Martian mantle. The solidus for the Martian composition falls above the solidus of MORB and below that of terrestrial peridotite, providing direct melting data for geophysical modeling of the Martian interior. Our solidus also predicts that a Martian mantle plume should produce melt at depths over a range of 200-350 km in the mantle. Plain Language Summary We simulated the interior of Mars by using high-pressure and high-temperature devices to determine how hot Mars must be to melt the solid rock inside the entire planet. We know that inside of Mars has melted (is melting?) because we observe large volcanoes on the surface, of various sizes and ages. We compared our results to data gained from the study of Martian meteorites, and determined that Mars could be melting today, in which case the upcoming InSight mission to Mars should see a signature of melting.