Venus is the second planet from the sun, at an average distance of 67 million miles. It is also the brightest object in the sky, 15 times brighter than the brightest star. Venus is difficult to study from earth, due to complete cloud cover and a thick atmosphere. The surface temperature on Venus is very uniform and is about 858 degrees Fahrenheit. The atmosphere of the planet is composed of almost entirely carbon dioxide. The clouds are made of sulfuric acid. Water vapor and water are extremely rare on Venus. One space probe revealed huge active volcanoes and large solidified lava flows.