Mechanical model of the solar system.

Mechanical model of the solar system.

Mechanical model of the solar system.

Mechanical model of the solar system.

Mechanical model of the solar system viewed from below.

Mechanical model of the solar system viewed from above, with a nebula in the background.

Mechanical model of the solar system viewed from above, with a nebula in the background.

Illustration of a quasar, viewed from an icy, rocky celestial body. Quasars (quasistellar objects, originally known as quasistellar radio sources), are very distant starlike bodies that have extremely high energy outputs.

Illustration showing comet Shoemaker Levy 9 with string of pearls. In 1994, July 16-22, pieces of the comet impacted Jupiter's southern hemisphere.

Illustration showing close binary star system.

Star on rim of total eclipse.

Digital Image of Earth and Moon in Space

Satellite and Earth

Computer Illustration

Optical image of Mars with an illustration showing it's core, mantle and crust. Current studies say its core consists primarily of iron with about 14-17% sulfur, and is about 1480 km in radius. The core is surrounded by a silicate mantle that formed many of the tectonic and volcanic features on the planet, but now appears to be inactive. The average thickness of the planet's crust is about 50 km, while the maximum thickness is about 125 km. In comparison, Earth's crust, averages 40 km, and is only one third as thick as the crust of Mars.

Optical image of Mars with an illustration showing it's core, mantle and crust. Current studies say its core consists primarily of iron with about 14-17% sulfur, and is about 1480 km in radius. The core is surrounded by a silicate mantle that formed many of the tectonic and volcanic features on the planet, but now appears to be inactive. The average thickness of the planet's crust is about 50 km, while the maximum thickness is about 125 km. In comparison, Earth's crust, averages 40 km, and is only one third as thick as the crust of Mars.

Illustration showing the core, mantle and crust of Jupiter; the fifth planet from the sun and the largest in the solar system. Jupiter has a rocky core and is surrounded by a dense metallic hydrogen layer, which extends outward to about 78 percent of the radius of the planet.

Illustration showing the core, mantle and crust of Jupiter; the fifth planet from the sun and the largest in the solar system. Jupiter has a rocky core and is surrounded by a dense metallic hydrogen layer, which extends outward to about 78 percent of the radius of the planet.

Illustration showing the core, mantle and crust of Mercury. Geologists estimate that Mercury's core occupies about 42% of its volume; in comparison, for Earth this proportion is 17%. Recent research suggests that Mercury has a molten core with a mantle of silicates, 500-700 km thick, surrounding it. Mercury's crust is believed to be 100-300 km thick based on data gathered from earth based observation, and the mariner 10 mission.

Illustration showing the core, mantle and crust of Mercury. Geologists estimate that Mercury's core occupies about 42% of its volume; in comparison, for Earth this proportion is 17%. Recent research suggests that Mercury has a molten core with a mantle of silicates, 500-700 km thick, surrounding it. Mercury's crust is believed to be 100-300 km thick based on data gathered from earth based observation, and the mariner 10 mission.