The planets of our solar system are a colorful bunch. This doesn’t just include Earth, whose colors come from its clouds, its seas and its landforms. The colors of the other planets come from the gases in the clouds of their upper atmospheres or their surfaces.
Mercury is the closest planet to the sun, and if Pluto was still a planet it would be the second smallest. It’s a dun, brown-colored planet full of craters, much like earth’s moon. It has a mean surface temperature during the day of 407 degrees F. On the side that faces away from the sun the temperature is 346 degrees below zero F. Venus is about the same size as earth and glows so brightly when it’s full -- it has phases, like the moon -- that it’s called the morning or evening star. But close up its color looks muddy due to the entire planet being shrouded in clouds. The atmosphere is 100 miles thick and the mean temperature is 866.9 degrees F. The heat and pressure, which is 100 times that of earth, is so intense that landforms on Venus change regularly.
Mars is called the red planet because of the amount of iron oxide on its surface. It’s smaller than earth and it’s atmosphere is thinner, so unlike Venus, the colors of its surface can be seen.The white at the North Pole is water ice, and the white at the South Pole is carbon dioxide ice. Jupiter is the largest planet in the solar system. It’s a gas giant and the bands of brick-red, tan, whites, creams and yellows that we see are its atmosphere. The lower clouds are composed of water vapor and ice crystals and the upper clouds are thought to be made of ammonium hydrosulfide. The Great Red Spot is a cloud that’s three times the size of the earth and is on top of what to humans is a permanent storm on the planet. There are smaller red spots and white spots, all the result of an atmospheric turbulence.
Saturn is also a gas giant, not as colorful as Jupiter, with its beige cream bands around the planet and its spectacular complex of self colored rings. Saturn's upper clouds consist of ammonia and are less turbulent than Jupiter’s because it’s smaller and its gravity is weaker. It’s possible that there's much turbulence beneath the cloud cover. Uranus rotates on its side, and like Jupiter and Saturn is a gas giant. Its beautiful blue-green color is probably due to a concentration of methane in its upper atmosphere. Other elements on Uranus are hydrogen and helium, acetylene and other hydrocarbons.
Neptune is also a gas giant and is also blue green because of a haze of methane crystals in its upper atmosphere. Though it’s about as big as Uranus, it radiates more heat than it absorbs. Its gravity and mass are higher than that of Uranus.
- "A Field Guide to the Stars and Planets"; Donald H. Menzel, et. al.; 1983
- "The Atlas of the Solar System"; Bill Yenne; 1987