火星巨型洪水地貌研究进展

Advance on the Martian megaflood geomorphology: a preliminary review

关键词:  火星洪水地貌学  形态学  水文重建  行星地貌学

Key words:  Martian flood geomorphology  morphology  hydrological reconstruction  planetary geomorphology

摘要:

火星水活动历史与洪水地貌研究是行星地貌与古洪水学科的标志性进展。文章根据火星多源探测数据和数值模拟成果，通过类比分析地球大陆尺度巨型洪水 （＞10⁶ m³ /s） 地貌景观，发现火星拥有太阳系中最大规模的峡谷和河网地貌，其规模可达地球已知最大洪水的10—100倍；通过重点梳理分析火星洪水侵蚀与沉积地貌形态特征、时空分布、水文重建等方面的特殊性，总结出5种典型的洪水地貌：干瀑布、网状河道、流线型山丘、纵向沟槽、边滩坝。这些洪水地貌主要分布在水手峡谷和大型冲积平原的边缘地带，洪水时间跨度大且成因过程随着火星诺亚纪、西方纪和亚马逊纪不同地质演变阶段而变化。 基于跨行星的洪水地貌研究，揭示巨型洪水形态学特性与机制，可为评估未来极端水文演变趋势与宜居行星提供科学依据。

Abstract:

Background, aim, and scope Understanding Martian megafloods is crucial for reconstructing the evolution of landforms on early Mars. The exploration and interpretation of Martian fluvial landscape and flood geomorphology are considered to be one of the landmark achievements in international palaeofloods research, as well as a frontier topic in planetary geomorphology. This study aims to deepen the scientific understanding of megafloods by advancing domestic research in China’s flood community, with implication for comprehending analogous events on the Tibetan Plateau and future catastrophic floods on Earth. Materials and methods Using a comparative and literature-integrated approach, we analyze the mechanisms, typical cases, and key features of Martian megafloods. This is achieved by analogizing their geomorphological evidence and spatial distribution with terrestrial continent-scale flood landforms on Earth. Results High-resolution imagery and advanced Marsspecific exploration technologies reveal that Mars hosts the most extensive canyon and river network in the solar system. The recorded flood magnitudes there surpass the magnitude of the largest known prehistoric floods on Earth by 10—100 times. We find five major megaflood landforms on Mars include cataracts, channel anastomosis, streamlined hills and islands, longitudinal grooves and giant bars. Discussion A comparative analysis of flood landforms between Mars and the earth is presented in three aspects. Firstly, the landform types, characteristics and its similarities and differences with the Earth’s flood landform are described. We argue that a single landform is insufficient to identify a megaflood, instead, a combination of erosional and depositional features must form a robust evidential chain. Secondly, within the distinct geological and climatic history of Mars, we have figure out the evolutionary timeline of Martian flood events, which are divided into three stages: the Noachian, the Hesperian, and the Amazonian. Notably, Martian megaflood occurred intensively during the Noachian to the Hesperian transition. Thirdly, we summarize the methods hydrological reconstruction of Martian flood, noting that their reliability remains limited due to incomplete geological evidence and a lack of highprecision topographic data constating flood water level. Conclusions Martain megaflood landforms are primarily occur in Valles Marineris and along the margins of major alluvial plains. Catastrophic lake drainage and groundwater eruptions are among probable triggering mechanisms for those megafloods. The three main geological periods on Mars were each marked by distinct environmental instability, which led to significant shifts in flood generation mechanisms. Consequently, current hydrological reconstructions focus mainly on outflow channel floods and palaeo-lake outburst events. Recommendations and perspectives We propose the following future research directions: (1) establishing a complete sedimentary system and spatiotemporal pattern of Martian flood landforms; (2) conducting analogy analysis between Martian megafloods and complex chain disasters on Earth, particularly those the Tibetan Plateau; (3) expanding research on flood geomorphology on other planetary bodies. Such work is vital for understanding climate and environment change in the early Martain history and assessing future habitable environment on Earth.