Often in the news or in magazines, we see beautiful pictures of bright, colorful planets. These photos are either taken through special filters or touched up afterwords. This is done in order to bring out greater details of the 8 planets.
Mercury is difficult to get a good picture of for a number of reasons. The planet’s proximity to the Sun makes it nearly impossible to get clear pictures of from the Earth, so the only decent photographs have come from spacecrafts, such as NASA’s Mariner 10. The surface of Mercury is very similar to the surface of our Moon; it is a grey planet covered with craters. The color of the surface comes from the iron and other heavy compounds that comprise the rocky surface of the planet. Because Mercury has almost no atmosphere, photographs capture its rocky surface.
Venus appears to be a yellowish color, which is caused by sulfuric acid in the thick atmosphere of the planet. The actually surface of the planet, when not seen through the yellow atmosphere, is an iron-grey color, similar to the surface of Mercury and the Moon.
The Earth, as seen from space, is an orb of blue with patches of white, green, and brown. Seventy percent of the Earth’s surface is water, which is where the blue come from. Earth has a thick atmosphere that protects the planet from harmful radiation and from space looks like white clouds. Depending on cloud coverage, Earth’s terrain and green foliage can also be seen from space.
Mars is famous for its reddish color, which caused the Ancient Romans to name the planet after their god of war. The red color results from rust in the rocks on the surface, which are visible because there is almost no cloud coverage on Mars.
Jupiter is composed of various gases including hydrogen and helium. Like Venus, Jupiter has sulfur in its environment, which gives it a dirty yellowish hue. There are also spots of other colors on the planet as a result of the violent storms that occur there. The Great Red Spot is the most famous storm on the planet.
Saturn is a gas planet with bands of orange and white. Ammonia forms the clouds of white, while ammonia hydrosulfide creates the orange clouds. In photographs, this planet is often colored more vibrantly with yellows and reds.
Uranus is light blue-green because there is a large amount of methane gas in the planet. Methane gas absorbs the color red, which means that it bounces back colors from the blue-green side of the spectrum. The colors that bounce back are recorded in photographs and make Uranus blue-green. Some touched-up photos of Uranus, taken by Voyager 2 in 1986, showed the planet as a bright green orb, but that is not the case.
Neptune is also blue because there is a significant amount of methane in the planet. Neptune is a slightly darker blue than Uranus because it is farther from the Sun. Even though they may not be the same vibrant orbs found in magazines, the planets are still stunning objects.
Astronomy Cast has episodes on all of the planets, so start with Mercury and listen to all of them.