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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

"The Day the Earth Smiled"

In this rare image taken on July 19, 2013, the wide-angle camera on NASA's Cassini spacecraft has captured Saturn's rings and our planet Earth and its Moon in the same frame.

Filed under pics of Earth by planetary missions, Cassini, pretty pictures, Earth, the Moon, Saturn, many worlds, Saturn's rings

Saturn from the south, with bonus Tethys

Saturn from the south, with bonus Tethys

Cassini viewed Saturn from a position well south of the ring plane on August 19, 2012. Just at the top edge of the image is a little icy moon, Tethys. Pandora is also in the frame but is too small and dim to be visible in this version of the image.

Filed under pretty pictures, Tethys, Cassini, amateur image processing, global views, Saturn's moons, many worlds, Saturn, Saturn's rings

Saturn looming over Titan

Saturn looming over Titan

Cassini spotted Titan beyond Saturn's limb on July 2, 2012. The south polar vortex that formed after winter arrived at Titan's south pole is visible. The atmosphere in Saturn's winter (southern) hemisphere is also taking on a methane-blue tinge.

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

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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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