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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

Saturn and Titan

Saturn and Titan

Cassini captured this stunning view of Saturn and Titan from nearly behind the pair on August 11, 2013.

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

Four moons and a ring

Four moons and a ring

On September 17, 2011 at about 1200 UTC, Cassini pointed at the mid-sized moon Dione and watched as it transited Titan while the rings and two small moons passed by. Pan is a tiny object orbiting within the A ring's Encke gap, while Pandora is the outer shepherd satellite of the F ring.

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

Pioneer 10 departs Jupiter (and Io)

Pioneer 10 departs Jupiter (and Io)

This is a parting shot of Jupiter and Io, taken December 5, 1973, by the Pioneer 10 spacecraft, the first to see either world as a crescent.

Filed under Jupiter's moons, Io, pretty pictures, amateur image processing, Pioneer 10 and 11, global views, many worlds, Jupiter

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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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Fly to an Asteroid!

Travel to Bennu on the OSIRIS-REx spacecraft!

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