火星一直是科学家寻找地外生命的热门目标。一项新研究首次确定了火星上规模最大的16个古河流域，被视为最有希望寻找生命的区域。
In a study published in
Proceedings of the National Academy of Sciences of the United States of America
PNAS), researchers from The University of Texas at Austin report the first detailed identification of large river drainage systems on Mars. Their analysis pinpointed 16 extensive river basins that would have offered the most promising settings for life on the red planet.
由大型河流系统塑造的区域是地球上最富饶的生态系统，地球上有91个超过10万平方公里的流域，仅亚马孙河流域就孕育了数万已知物种。科学家们认为，古代火星也有类似环境，曾经存在有液态水的时期，可能为生命提供了有利条件。
美国得克萨斯大学奥斯汀校区的研究人员通过收集并分析之前发表的关于火星山谷、湖泊和河流特征的数据发现，火星上有19个主要的山谷、溪流、湖泊、峡谷和沉积物群，其中有16个形成了面积至少达10万平方公里、相互连接的流域。
Their work revealed 19 major groupings of valleys, streams, lakes, canyons, and sediment deposits. Of these, 16 formed interconnected watersheds covering at least 100,000 square kilometers. On Earth, that size marks the lower limit of what scientists define as a large drainage basin. This marks the first systematic, planet-wide effort to identify large river basins on Mars.
Large watersheds are far more common on Earth than on Mars. Our planet has 91 drainage basins that exceed 100,000 square kilometers.
研究人员认为，大型河流可输送更多营养物质，有助于维持多样的生态系统。水流经距离越远，水与岩石的相互作用就越多，发生化学反应的机会就更高，这些反应可能转化为生命迹象。
研究人员表示，虽然这些大型流域只占火星地表面积的5%左右，却贡献了火星河流侵蚀沉积物的约42%。由于沉积物携带营养物质，这些地点被认为是寻找过去生命证据的主要目标，但需要进一步研究以精确确定这些沉积物最终的沉积位置。
The researchers found that Mars' largest drainage systems played an outsized role in shaping the planet. Although they cover only about 5 percent of ancient Martian terrain, these regions account for roughly 42 percent of all material eroded by rivers on Mars.
研究结果已发表在美国《国家科学院学报》（PNAS）上。
来源：新华社 环球网 Science Daily
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