Faculty of Geosciences, Utrecht University, Princetonlaan 8a, Utrecht, 3584 CB, The Netherlands.
International Research School of Planetary Sciences, Università Gabriele D'Annunzio, Viale Pindaro 42, Pescara, 65127, Italy.
Nat Commun. 2020 May 5;11(1):2067. doi: 10.1038/s41467-020-15622-0.
Orbital observation has revealed a rich record of fluvial landforms on Mars, with much of this record dating 3.6-3.0 Ga. Despite widespread geomorphic evidence, few analyses of Mars' alluvial sedimentary-stratigraphic record exist, with detailed studies of alluvium largely limited to smaller sand-bodies amenable to study in-situ by rovers. These typically metre-scale outcrop dimensions have prevented interpretation of larger scale channel-morphology and long-term basin evolution, vital for understanding the past Martian climate. Here we give an interpretation of a large sedimentary succession at Izola mensa within the NW Hellas Basin rim. The succession comprises channel and barform packages which together demonstrate that river deposition was already well established >3.7 Ga. The deposits mirror terrestrial analogues subject to low-peak discharge variation, implying that river deposition at Izola was subject to sustained, potentially perennial, fluvial flow. Such conditions would require an environment capable of maintaining large volumes of water for extensive time-periods, necessitating a precipitation-driven hydrological cycle.
轨道观测揭示了火星上丰富的河流地貌记录，其中大部分记录可追溯到 36-30 亿年前。尽管有广泛的地貌证据，但对火星冲积沉积地层记录的分析很少，对冲积物的详细研究主要限于较小的砂体，这些砂体适合漫游者在原地进行研究。这些通常是米级尺度的露头尺寸，妨碍了对更大尺度河道形态和长期盆地演化的解释，而这些对于了解过去火星气候至关重要。在这里，我们对西北 Hellas 盆地边缘的 Izola 台地的一个大型沉积序列进行了解释。该序列由河道和沙洲包络组成，共同表明河流沉积早在 37 亿年前就已很好地建立起来。这些沉积物反映了受低峰值流量变化影响的陆地类似物，这意味着 Izola 的河流沉积受到持续的、可能是常年的、河流流动的影响。这种条件需要一个能够维持大量水的环境，以维持较长时间，这需要一个由降水驱动的水文循环。
