Three dark splotches mark the tops of these lava flows. Because of the thick atmosphere surrounding Venus, small impactors break up before they hit the surface. Thefragments are deposited over the surface and produce the dark splotches seenhere. Notice the splotch on the far right has a crater at its center,indicating that the impactor was not completely destroyed. Arachnoids Named by the Soviets for their spider and cobweb-like appearance, arachnoids are one of the more remarkable features found on Venus.
Arachnoids are similarin form but generally smaller than coronae.
The radar- bright lines extending for many kilometers beyond the arachnoids may have been caused byan upwelling of magma from the interior of Venus, which pushed up the surface to form cracks. Two large oval features can be seen in this image of Fortuna. Both features are surrounded by a ring of ridges and troughs. The central areas of the coronae contain radial fractures as well as volcanic domes and flows. Coronae may form due to the upwelling of hot material from deep in the interior of Venus.