The Inner Planets: Mercury, Venus, and Mars

The Inner Planets: Mercury, Venus, and Mars — page 1
ince ancient times humans have gazed in wonder at the vast blanket of stars covering the night sky Records going back 5 000 years show that ancient Sumerian astronomers recognized that some stars moved differently than other celestial bod ies Three special objects they tracked are the three closest planets to Earth Mercury Venus and Mars These objects still fascinate today This book will take you on a journey to learn about our neighbors in the solar system The first stop on our tour will be tiny Mercury At less than two fifths Earth s size it is the smallest of the eight planets Because it is the closest planet to the Sun it can complete an orbit around the Sun in only 88 Earth days But it takes almost 59 Earth days to complete one rotation about its axis Mercury has almost no atmosphere leaving its dry and rocky surface little protection from crater blasts by asteroids Mercury is the densest planet in the solar system Our second stop is Venus the solar sys tem s third smallest planet and the one most similar in size to Earth Venus's atmosphere is remarkably massive Made mostly of thick heat trapping layers of carbon dioxide the heavy atmosphere makes it the hottest planet