This research explores how hydrogen affects the stability of iron–sulfur (Fe–S) alloys at the extreme pressures and temperatures found in the deep interiors of Mars and Mars-like exoplanets. While meteorites tell us that Mars's core likely contains iron, sulfur, and some nickel, recent seismic data from NASA’s InSight mission suggests that Mars's core is larger and less dense than expected—hinting that more light elements like hydrogen may be present.

To understand this, we conducted high-pressure, high-temperature experiments on Fe–S materials in hydrogen-varying environments. Our findings show that hydrogen can destabilize certain Fe–S compounds and promote the formation of hydrogen-rich metallic liquids. These results help explain why Mars's core might still be mostly molten today and offer new clues about the interior makeup of similar rocky planets beyond our solar system.