Partially melted low velocity zones reveal an active upper mantle beneath Elysium Planitia, Mars

The current state of Mars's interior is fundamental to understanding its thermal evolution, volcanic history, and potential habitability. While global-scale magmatism has declined since the Amazonian epoch, recent volcanism and concentrated seismicity in Elysium Planitia suggest localized, ongoing mantle activity, yet direct evidence has remained elusive. Here, we analyze InSight seismic data, combining receiver functions and PP/SS precursors to image crustal and upper mantle structures beneath three locations in Elysium Planitia. We identify consistent low-velocity zones at depths of ~70-100 km, marked by shear wave velocity reductions up to 36%. These anomalies are best explained by adiabatic decompression melting within a high-temperature upper mantle, with estimated melt fractions of 2-12%, potentially aided by the presence of water. Our results provide direct seismic evidence for partial melting and active dynamic mantle processes beneath Elysium Planitia, likely driven by a mantle plume, suggesting that Mars's interior remains thermochemically active today.