英国伦敦帝国理工学院Steven G. Banham团队报道了作为火星盖尔陨石坑晚期浅层地下水证据的沉积物变形构造。这一研究成果发表在2024年3月22日出版的国际学术期刊《地质学》上。

研究人员称，在填坑初期，水环境下的沉积作用明显，此时，sharp山群下部地层的堆积以河湖沉积岩为特征。锡卡点群的基底单元Stimson组不整合地覆盖在sharp山群之上，代表了Aeolis山发掘后的条件，其特征是在干旱条件下形成风成地层堆积。在其沉积过程中，地表附近基本上没有水。在Feòrachas露头处，在风成地层中发现的软沉积物变形结构，挑战了盖尔陨石坑在后期沉积阶段缺乏水的观念。

研究确定了变形的风成波纹层和垂直层压砂岩，分布于形成箱型结构的耐侵蚀的山脊内。总的来说，这些结构是浅层地下水(液态或冰态)。与地球类似物的比较表明，地层是由地下流体逸出、冻融过程或蒸发岩变形形成的。不管其机制如何，这些结构表明盖尔陨石坑表面或附近存在水的时间比之前记录的要晚得多，并且可能延长盖尔陨石坑的宜居时间。

据悉，在盖尔陨石坑的后期演化过程中，近地表水的持续存在，可能是维持宜居环境的基础。

附：英文原文

Title: Ice Salt Pressure Sediment deformation structures as evidence of late-stage shallow groundwater in Gale crater, Mars

Author: Steven G. Banham, Amelie L. Roberts, Sanjeev Gupta, Joel M. Davis, Lucy M. Thompson, David M. Rubin, Gerhard Paar, Kirsten L. Siebach, William E. Dietrich, Abigail A. Fraeman, Ashwin R. Vasavada

Issue&Volume: 2024-03-22

Abstract: Persistence of near-surface water during the late evolution of Gale crater, Mars, would have been fundamental for maintaining a habitable environment. Sedimentation in aqueous conditions is evident during the early stages of crater infilling, where accumulation of lower Mount Sharp group strata is characterized by fluviolacustrine sedimentary rocks. The basal unit of the Siccar Point group—the Stimson formation—which unconformably overlies the Mount Sharp group and represents conditions postdating the exhumation of Aeolis Mons, is characterized by accumulation of aeolian strata under arid conditions. Water was largely absent near the surface during its deposition. At the Feòrachas outcrop, discovery of soft sediment deformation structures in aeolian Stimson strata challenges the notion that Gale crater was devoid of water during its later depositional phase. We identified deformed wind-rippled and vertically laminated sandstones, hosted within erosion-resistant ridges forming boxwork patterns. Broadly, these structures are diagnostic of water (as liquid or as ice) in the shallow subsurface. Comparison with Earth analogues suggests formation by subsurface fluid escape, freeze-thaw processes, or evaporite deformation. Regardless of the mechanism, these structures signify the presence of water at or near the surface much later than previously documented and may extend the habitability window in Gale crater.

DOI: 10.1130/G51849.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G51849.1/636785/Ice-Salt-Pressure-Sediment-deformation-structures