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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

Terra Cognita

Terra Cognita

Pushing back the frontiers of the unknown. On the left: destinations in the Solar System as seen by historic robotic spacecraft and telescopes. On the right: the same worlds as seen by recent missions that have filled in some of the blank spaces on the map. Click the image for the full-size version.

Filed under pretty pictures, many worlds, Mercury, the Moon, Mars, Titan, asteroids, asteroid 1 Ceres, asteroid 4 Vesta, Pluto, Mariner 10, MESSENGER, Soviet lunar missions, Lunar Reconnaissance Orbiter, NASA Mars missions before 1996, Mars Reconnaissance Orbiter, Voyager 1 and 2, Cassini, New Horizons, Dawn

Dunes on Earth and Titan

Dunes on Earth and Titan

Left: Dune interactions with topographic obstacles in Namibia as seen on Google Earth. Right: Cassini radar image of the Belet sand sea on Titan, obtained during T8, 300 m resolution.

Filed under Cassini, pretty pictures, Titan, scale comparisons, Saturn's moons, radar imaging

Earth and Moon from Elektro-L

Earth and Moon from Elektro-L

Earth and its moon as viewed by the Russian weather satellite Elektro-L, which is in a geostationary orbit 36,000 kilometers from Earth.

Filed under Earth observing missions, pretty pictures, amateur image processing, Earth, the Moon, global views, 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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Fly to an Asteroid!

Travel to Bennu on the OSIRIS-REx spacecraft!

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