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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

Earthrise from Lunar Orbiter 1

Earthrise from Lunar Orbiter 1

On August 23, 1966, Lunar Orbiter 1 took the first photo of Earth as seen from lunar orbit. While a remarkable image at the time, the full resolution of the image was never retrieved from the data stored from the mission. In 2008, this earthrise image was restored by the Lunar Orbiter Image Recovery Project at NASA Ames Research Center. They obtained the original data tapes from the mission (the last surviving set) and restored original FR-900 tape drives to operational condition using both 60s era parts and modern electronics. A 1.2 GB full resolution version of the image is available from NASA here.

Filed under pics of Earth by planetary missions, NASA lunar missions before 2005, pretty pictures, Earth, the Moon, many worlds

Europa Rises

Europa Rises

In this dramatic shot from the New Horizons flyby of Jupiter, it observed Europa, the smallest of the four Galilean moons of Jupiter, rising above the vast limb of Jupiter. This was one of seven observations made by New Horizons for primarily aesthetic rather than scientific reasons.

Filed under Jupiter's moons, New Horizons, pretty pictures, Europa, many worlds, Jupiter

Pluto and its Moons

Pluto and its Moons

Pluto, Charon, Nix, and Hydra, as observed by the Hubble Space Telescope on February 15, 2006.

Filed under trans-neptunian objects, Hubble Space Telescope, pretty pictures, Pluto, Charon, Eris, 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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Space in Images

Pretty pictures and
awe-inspiring science.

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