Venus: Sinuous channel 4.8
130 km wide Magellan image showing a 2 km wide sinuous channel crossing fractured lava plains (49°South, 273°East).
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Image Credit: NASA  

This is one of about 200 sinuous channels on the plains of Venus, the longest of which has been traced for an amazing 6800 km. Superficially these resemble meandering river channels, but generally speaking they lack tributaries. Given that Venus's surface temperature is likely to have been hot for a long time past, thye are most unlikely to have been cut by flowing water. They could be channels cut by basalt lava, or some other, less viscous, variety of silicate magma. However, the erosive power of such lava, and its ability to remain molten for long enough to travel the length of a channel have both been questioned. An alternative possibility is that they were carved by flows of carbonatite , a lava composed largely of calcium carbonate. Because carbonatite does not solidify until it colls below 600 degrees C, it could remain liquid for a long time after eruption onto the hot surface of Venus.  
text credit: David A Rothery Return to top of page