Xiaoxin Wang

and 2 more

While an early wet Mars is well established along many lines of scientific evidence, it remains vigorously debated in what forms water existed in the early Mars and how Mars transitioned from a wet planet into a dry planet. Here, we construct a detailed seismic stratigraphy from the source region of a marsquake in Cerberus Fossae to the InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) landing site to decipher the evolution of Mars. Seismic velocity structures are constrained with combined seismic constraints of waveforms recorded for the marsquake and receiver functions extracted from the seismic data of three marsquakes, while the crustal composition and pore property are inferred based on rock physics modeling of the inferred seismic structure and constraints of porosity-depth profiles beneath Mars. Seismic stratigraphy reveals a liquid-water saturated smectite-chlorite-enriched sedimentary layer at 2.65-3.85 km beneath Martian surface and a transition from the dry surface basaltic layer to liquid-water saturated overlain crustal layers, suggesting that early wet Mars experienced a paleo-ocean and a resurface event in the northern plain before transitioning into a dry planet and covered by the emplacement of the Elysium volcanic unit in Hesperian and Amazonian. Our results indicate that the major early records of planetary water history are buried deep in the Martian crust, and so is the possible evidence of early life on Mars. Magmatic perturbations of the deep water reservoir would also provide an explanation for possible subsequent oceans proposed at different stages of the Martian history.