Atmosphere of Venus
The atmosphere of Venus is the layer of gases surrounding Venus. It is composed primarily of carbon dioxide and is much denser and hotter than that of Earth. The temperature at the surface is 740 K (467 °C, 872 °F), and the pressure is 93 bar (9.3 MPa), roughly the pressure found underwater on Earth. The Venusian atmosphere supports opaque clouds made of sulfuric acid, making optical Earth-based and orbital observation of the surface impossible. Information about the topography has been obtained exclusively by radar imaging. Aside from carbon dioxide, the other main component is nitrogen. Other chemical compounds are present only in trace amounts.
Surface features of Venus
Impact craters are roughly circular shaped depressions in the surface of a planet due to high velocity impacts with extraterrestrial bodies. The surface of Venus contains almost 1000 impact craters. However, unlike some planets in our system, Venus' thick atmosphere creates a strong shield that decelerates, flattens, and can fracture incoming projectiles. The Venusian surface is devoid of small craters (≤30–50 km in size) because of the effect the atmosphere has on small bodies. Depending on the angle of impact, velocity, size, and strength of the approaching body, the atmosphere may tear and crush the projectile, essentially melting it in the air. This is an important observation for studies of the surface of Venus, as crater are used to determine relative ages and to approximate absolute ages of surface features.