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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

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

ISON, Encke, Mercury, and Home

ISON, Encke, Mercury, and Home

On November 21, 2013, comet C/2012 S1 (ISON) entered the field of view of NASA's STEREO "Ahead" spacecraft's HI-1A camera. It joined Earth, Mercury and comet 2P/Encke!

Filed under pics of Earth by planetary missions, Mercury, comets, Earth, many worlds, animation

In Saturn's Shadow (The Day the Earth Smiled)

In Saturn's Shadow (The Day the Earth Smiled)

On July 19, 2013 Cassini passed into Saturn's shadow and turned toward the Sun, capturing an image of the planet's night side and the weirdly lit semi-transparent rings. Cassini also captured seven of the moons and three planets. This was the third time our home planet was imaged from the outer solar system; the second time it was imaged by Cassini from Saturn's orbit; and the first time ever that inhabitants of Earth were made aware in advance that their photo would be taken from such a great distance.

Filed under Enceladus, Cassini, Tethys, Saturn's small moons, global views, Saturn's moons, many worlds, Saturn, Mimas, Saturn's rings, pretty pictures, best of, Venus, Earth, the Moon, Mars

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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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