This image is a mosaic of Magellan orbits 385-399. It covers a region 370 kilometers (220 miles) wide and 455 kilometers (270 miles) high, centered at about 30 degrees north latitude, 335 south longitude, in southeast Guinevere Planitia in the Navka Region of Venus. Trending from lower right toward upper left of the image is a long, sinuous, radar-dark rille-like feature. This rille is about 500 kilometers (300 miles) long in this image, and it has been traced for approximately an additional 500 kilometers to the east where its source may lie buried beneath younger plains volcanics. The rille maintains a nearly constant width of between 750 meters (230 feet) and 2 kilometers (1.2 miles) throughout its length. It appears to terminate in the broad, radar-dark V-shaped plains unit at the upper left. The margins of the rille are bright in the radar, suggesting levees similar to terrestrial lava channel levees. In addition, a number of faint, apparently abandoned rilles branch off the main rille, suggesting that flow was maintained for a relatively long time. Its great dimensions and implied longevity are likely due to the ability of lava in Venus' high temperature environment to remain fluid and thermally erode terrain over great distances when compared to terrestrial lava flows.
