法国图卢茨大学Rapin, W.团队在研究早期火星上持续的干湿循环中取得新进展。这一研究成果于2023年8月9日发表在国际顶尖学术期刊《自然》上。

研究人员报告了好奇号火星探测车在盖尔陨石坑的观察结果，表明早期火星表面环境中出现了高频率的干湿循环。研究观察到富含硫酸盐的厘米级多边形山脊，在 Y 型连接处连接，记录了由于常规强度的反复干湿循环而在新鲜泥浆中形成的裂缝。研究人员指出了早期火星上持续的、循环的、可能是季节性的气候，而不是由撞击或火山引起的零星水文活动。

此外，由于干湿循环可以促进前生物聚合，盖尔蒸发岩盆地可能特别有利于这些过程。研究观察到的多边形模式在物理上和时间上都与蒙脱石粘土向含硫酸盐地层的过渡有关，这是一种全球分布的矿物过渡。这表明 Noachian–Hesperian 过渡时期( 38-36 亿年前)可能维持了类似地球的气候制度和有利于前生物进化的地表环境。

据介绍，早期火星上常年潮湿表面环境的存在已经被研究者们很好地记录下来，但对早期水文气候中的短期附带性知之甚少。由这种短期波动驱动的沉积后过程可能产生独特的结构，但这些结构很少保存在沉积记录中。不完全的地质限制导致早期火星水文循环和气候的全球气候模型产生了不同的结果。

附：英文原文

Title: Sustained wet–dry cycling on early Mars

Author: Rapin, W., Dromart, G., Clark, B. C., Schieber, J., Kite, E. S., Kah, L. C., Thompson, L. M., Gasnault, O., Lasue, J., Meslin, P.-Y., Gasda, P. J., Lanza, N. L.

Issue&Volume: 2023-08-09

Abstract: The presence of perennially wet surface environments on early Mars is well documented, but little is known about short-term episodicity in the early hydroclimate. Post-depositional processes driven by such short-term fluctuations may produce distinct structures, yet these are rarely preserved in the sedimentary record. Incomplete geological constraints have led global models of the early Mars water cycle and climate to produce diverging results. Here we report observations by the Curiosity rover at Gale Crater indicating that high-frequency wet–dry cycling occurred in early Martian surface environments. We observe exhumed centimetric polygonal ridges with sulfate enrichments, joined at Y-junctions, that record cracks formed in fresh mud owing to repeated wet–dry cycles of regular intensity. Instead of sporadic hydrological activity induced by impacts or volcanoes, our findings point to a sustained, cyclic, possibly seasonal, climate on early Mars. Furthermore, as wet–dry cycling can promote prebiotic polymerization, the Gale evaporitic basin may have been particularly conducive to these processes. The observed polygonal patterns are physically and temporally associated with the transition from smectite clays to sulfate-bearing strata, a globally distributed mineral transition. This indicates that the Noachian–Hesperian transition (3.8–3.6billion years ago) may have sustained an Earth-like climate regime and surface environments favourable to prebiotic evolution.

DOI: 10.1038/s41586-023-06220-3

Source: https://www.nature.com/articles/s41586-023-06220-3