It is a near twin of Earth in size, mass, and density. Venus's diameter is about 7,521 miles (12,104 kilometers), compared with some 7,926 miles (12,756 kilometers) for Earth.Its mass is approximately 80 percent of Earth's, and its density is about 95 percent of Earth's.The surface gravity of the two planets is also of similar.Venus...enus's diameter is about 7,521 miles (12,104 kilometers), compared with some 7,926 miles (12,756 kilometers) for Earth. Its mass is approximately 80 percent of Earth's, and its density is about 95 percent of Earth's. The surface gravity of the two planets is also of similar. Venus...