Compare the Planets
Comparing the physical characteristics of the worlds in our solar system (and beyond)
The worlds of our solar system come in all shapes, sizes, and colors. Red-eyed Jupiter, ringed Saturn, and frigid Uranus and Neptune are giant gassy globes containing nearly all of the matter in the solar system. These Jovian planets, or gas giants, are huge worlds of air, clouds, and fluid that may have no solid surfaces no matter how deep you go. Everything else in the solar system is just rock, ice, and dust. The largest rockballs are known as the terrestrial planets: Mercury, Venus, Earth, and Mars, with our Moon usually considered part of the club, and now Vesta is applying for membership. Earth is the biggest of all the rocky worlds.
But the planets are not the only worlds of the solar system. All but two of the planets are orbited by moons, each of them a world unto itself. The largest moons are bigger than the smallest planets, and 16 or 17 would qualify as dwarf planets if they orbited the Sun. There are more than 100 Kuiper belt dwarf planets, but only one among the asteroids, Ceres.
Six solid worlds -- Venus, Earth, Mars, Titan, Triton, and Pluto -- have atmospheres dense enough to produce weather. Eris likely does, when it is near its perihelion. We have witnessed active geology on four worlds -- Earth, Io, Enceladus, and Triton -- and we suspect it on Venus, Europa, and Titan. Comparing the same processes across many worlds helps us to understand how each planet's unique composition and history influence its present state, and will help us predict what to expect on Earth in the future.
Pretty Pictures with Many Worlds
Lunar Reconnaissance Orbiter used both narrow- and wide-angle cameras to capture this view of a colorful Earth beyond the lunar limb on October 12, 2015. The Moon's surface is a grayscale narrow-angle camera photo; Earth has been colorized with wide-angle camera data. Read more about how this photo was created at the Lunar Reconnaissance Orbiter Camera website. Download a full-resolution PNG version here (53 MB).
Hayabusa2 used its optical navigation telephoto camera (ONC-T) to capture this view of Earth and the Moon together on November 26, 2015 at 03:46 UT, or 12:46 Japan time. The image is made of three distinct images captured through red, green, and blue filters, and has been processed to align the different-filter images with each other. North is to the left; Asia and Australia are visible on the lit face of Earth. Hayabusa2 was on the way in to its December 3, 2015 flyby of Earth.
Space rarely makes a strong showing in national elections, despite the major state of transition NASA finds itself in today.
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