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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

Earth and Moon from Juno

Earth and Moon from Juno

This image of Earth (on the left) and the moon (on the right) was taken by JunoCam on the Juno spacecraft, three weeks after its August 5 launch. On August 26, 2011, the spacecraft was already almost 10 million kilometers away from the Earth-Moon system.

Filed under pics of Earth by planetary missions, pretty pictures, Earth, the Moon, many worlds, Juno

Super high-resolution global view of Dione, plus rings

Super high-resolution global view of Dione, plus rings

This super high-resolution view of Dione is a mosaic of 14 footprints, images taken through infrared, green, and ultraviolet filters processed to approximate the color that the human eye would see. In the background, Saturn's ring system is foreshortened to a thin double yellow line.

Filed under Dione, pretty pictures, Cassini, amateur image processing, Saturn's moons, many worlds

ISON approaches the Sun as seen from STEREO-A (Nov 21-26, 2013)

ISON approaches the Sun as seen from STEREO-A (Nov 21-26, 2013)

This animation is composed of 208 images captured over a period of five days from November 21 to November 26 as comet ISON approached the Sun. Also in the frame are Mercury, Earth, and comet Encke.

Filed under pretty pictures, Mercury, comets, the Sun, Earth, many worlds, animation

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Section Highlights

Planetary Facts

Mass, diameter, density, gravity, orbital characteristics, presented both in metric units and measured relative to Earth.

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Asteroids and Comets Visited by Spacecraft

A comparison of all the asteroids and comets ever visited by spacecraft, up to date as of November 10 (when Deep Impact flew past Hartley 2). Vesta is not included.

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Every Round Object in the Solar System, to Scale

A correctly scaled, reasonably correctly colored view of the largest bodies in the solar system.

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Space in Images

Pretty pictures and
awe-inspiring science.

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