Effusive sedimentary volcanism experimentally reproduced under Martian-like conditions

Rapid boiling, cooling, and freezing are commonly assumed to rapidly quench metastable liquid eruptions exposed to near-vacuum planetary environments, influencing both sedimentary volcanism on Mars and cryovolcanism on icy worlds. However, how these coupled phase transitions govern eruptive processes remains largely unknown. Here we show experimentally that boiling instead sustains coupled ballistic-effusive mud eruptions under Martian-like pressure conditions (~4.5 mbar). Using an ice-sealed metastable reservoir, we reproduced subsurface-driven eruptions initiated by internally generated boiling-induced overpressure. Eruptions evolved systematically from short-lived ballistic fountains toward episodic effusive emplacement accompanied by coherent mud-flow formation. Ballistic transport redistributed liquid mud around the vent and promoted proximal accumulation that subsequently coalesced into sustained flows despite ongoing cooling and freezing. Numerical modeling further demonstrates that erupted mud would remain largely unfrozen during ballistic transport under Martian gravity conditions. Together, our results show that rapid boiling does not suppress sedimentary volcanism under low-pressure conditions, but instead actively sustains eruptive transport and surface emplacement. These findings provide new constraints on this process on Mars and establish a broader physical framework for metastable liquid eruptions across the Solar System.