Geologic Constraints on Early Mars Climate

摘要: Early Mars climate research has well-defined goals (MEPAG 2018). Achieving these requires geologists and modelers to coordinate. Coordination is easier if results are expressed in terms of parameters. Key parameters include the following quantitative geologic constraints. (1) Cumulative post-3.4 Ga precipitation-sourced water runoff some places exceeded $1~\mbox{km}$ column. (2) There no single problem: traces ≥2 river-forming periods seen. Relative rivers that formed earlier history, later history found preferentially at lower elevations, show a stronger dependence on latitude. (3) The duration longest individual was ${>}(10^{2}\mbox{--}10^{3})~\mbox{yr}$ , based paleolake hydrology. (4) Peak production ${>}0.1~\mbox{mm}/\mbox{hr}$ . However, (5) peak intermittent, sustained (in given catchment) for only <10% climates. (6) cumulative number wet years during valley-network-forming period ${>}10^{5}~\mbox{yr}$ (7) Post-Noachian light-toned, layered sedimentary rocks took ${>}10^{7}~\mbox{yr}$ accumulate. (8) an “average” place saw ${<}10^{7}~\mbox{yr}$ after Noachian, suggesting climates were interspersed with long globally-dry intervals. (9) Geologic proxies atmospheric pressure indicate not less than 0.012 bar but much more 1 bar. A truth table constraints versus currently published models shows late persistence climates, combined lake-forming challenge most models.