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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 not-planets

The not-planets

The solar system contains dozens of objects that are large enough for self-gravity to make them round, and yet are not considered planets. They include the major moons of the planets, one asteroid, and many worlds in the Kuiper belt. The ones that we have visited with spacecraft are shown here to scale with each other. A couple of items on here are not quite round, illustrating the transition to smaller, lumpier objects.

Filed under Enceladus, Dione, Tethys, Titan, Rhea, Iapetus, Dawn, Saturn's moons, Mimas, Jupiter's moons, Io, Pluto, Europa, scale comparisons, Ganymede, amateur image processing, Charon, Callisto, the Moon, asteroid 4 Vesta, New Horizons, Cassini, Galileo, asteroid 1 Ceres, pretty pictures, Triton, Neptune's moons, Uranus' moons

Pluto and Charon in color: LORRI + MVIC, July 8 & June 25, 2015

Pluto and Charon in color: LORRI + MVIC, July 8 & June 25, 2015

A LORRI image from July 8 has been colorized with much lower-resolution MVIC data taken June 25 to make this color view. Pluto and Charon were 6 million kilometers away at the time. Most of the bright features around Pluto's edge are a result of image processing, but the bright sliver below the dark "whale," which is also visible in unprocessed images, is real.

Filed under trans-neptunian objects, New Horizons, pretty pictures, Pluto, Charon, global views, dwarf planets beyond Neptune, many worlds

Pluto and Charon in color: LORRI + MVIC, June 21, 2015

Pluto and Charon in color: LORRI + MVIC, June 21, 2015

A lower-resolution MVIC color image from May was used to colorize a higher-resolution LORRI image to make this view of Pluto and Charon in color.

Filed under trans-neptunian objects, New Horizons, pretty pictures, Pluto, amateur image processing, Charon, dwarf planets beyond Neptune, many worlds

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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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