What are the true colors of each planet in our Solar system? I've seen the same planet colored differently in different photos.
Here are the true colors of the planets, with links to some relevant images from NASA spacecraft. (Note that spacecraft photos appearing in the media often have false coloration.)
- Mercury: gray (or slightly brownish). Mercury has practically no atmosphere, so we just see the rocky surface. Note that many images of Mercury (like this one) are grayscale, derived from a single color filter. Mercury's color variations are fairly subtle; the color variations are greatly exaggerated in this false color view.
- Venus: pale yellow. To human eyes, Venus looks kind of boring. We can only see the thick layer of featureless sulfuric acid clouds. Two of the Soviet Venera probes returned images from the surface of Venus. The colors from those Venera images were later used to colorize radar data from NASA's Magellan spacecraft, in order to generate simulated global views of the surface of Venus. You can find more on the colors of Venus here.
- Earth: mostly blue with white clouds. Oceans and light scattered by the atmosphere make Earth prevailingly blue. Depending on the area seen in an individual picture, brown, yellow and green continents can be seen or parts of Earth can be covered by white clouds. Earth is by far the most dynamic planet when seen from space.
- Mars: mostly reddish brown, though with some darker regions, and also white ice caps. The dominant reddish color comes from rusty rocks on the surface, since the clouds are rare and thin.
- Jupiter: orange and white bands. The white bands are colored by ammonia clouds, while the orange comes from ammonium hydrosulfide clouds. None of the four "gas giant" planets (Jupiter, Saturn, Uranus, and Neptune) has a solid surface, so all we see are just clouds in their atmospheres.
- Saturn: pale gold. White ammonia haze covers the whole planet and partially obscures redder clouds below. Clouds in Saturn's winter hemisphere are pale blue. Scientists think that because the rings are blocking the Sun in the winter hemisphere, things are colder there and the ammonia clouds are lower down than normal. This gives the rest of the atmosphere more of a chance to scatter light, just like the Earth's atmosphere does.
- Uranus: pale blue. The color comes from methane clouds. In some photos released after the Voyager 2 flyby (in 1986), Uranus looked green, but that color was artificial.
- Neptune: pale blue. As in the case of Uranus, the color is due to methane. Neptune would appear darker than Uranus due to dimmer illumination (greater distance from the Sun). Some of the images of Neptune from the Voyager 2 flyby (in 1989) show a deep blue color, but the colors in those images were enhanced. The actual colors of Uranus and Neptune are quite similar.
- Pluto (no longer a planet; now classified as a dwarf planet): mostly light brown, with some darker regions. Note that some of the images from NASA's New Horizons space probe (which flew past Pluto and its moons in 2015) have been enhanced to show color contrasts more clearly.
Also, I would like to add that the assignment of colors is somewhat subjective. For example, one person's "blue" might look more like "green" to somebody else. Astronomers rarely care about that, and we use precise spectra when we need to obtain quantitative information about an object's color.
Here are some good sites with more images of the planets (not always in true color!):
- NASA's Astronomy Picture of the Day (APoD): http://apod.nasa.gov/apod/astropix.html
- NASA/JPL Space Images: http://www.jpl.nasa.gov/spaceimages/
- NASA/JPL Photojournal: http://photojournal.jpl.nasa.gov/
And, here are some pages that explain how false color images are useful in astronomy:
This page was last updated by Sean Marshall on February 7, 2016.