刘文勇ibt黄金阅读12.3版本：火星上的流水

刘文勇ibt黄金阅读12.3版本：火星上的流水刘文勇ibt黄金阅读12.3版本:火星上的流水 刘文勇ibt黄金阅读12.3版本:RUNNING WATER ON MARS 火星上的流水 Photogr

刘文勇ibt黄金阅读12.3版本：火星上的流水 刘文勇ibt黄金阅读12.3版本:火星上的流水 刘文勇ibt黄金阅读12.3版本:RUNNING WATER ON MARS 火星 上的流水 Photographic evidence suggests that liquid water once existed in great quantity on the surfaceof Mars. Two types of flow features are seen: runoff channels and outflow channels. Runoff channelsare found in the southern highlands. These flow features are extensive systems—sometimeshundreds of kilometers in total length—of interconnecting, twisting channels that seem to merge intolarger, wider channels. They bear astrong resemblance to river systems on Earth, and geologiststhink that they are dried-up beds of long-gone rivers that once carried rainfall on Mars from themountains down into the valleys. Runoff channels on Mars speak of atime 4billion years ago (theage of the Martian highlands), when the atmosphere was thicker, the surface warmer, and liquidwater widespread. Outflow channels are probably relics of catastrophic flooding on Mars long ago. They appearonly in equatorial regions and generally do not form extensive interconnected networks. Instead, theyare probably the paths taken by huge volumes of water draining from the southern highlands into thenorthern plains. The onrushing water arising from these flash floods likely also formed the oddteardrop-shaped “islands” —————————————————————————————————