The inner core, meanwhile, has greater density, at 13, and temperature, at 6,650°C (or 12,000°F). Compared against other planets in the solar system, the Earth contains just the appropriate amounts of gases, elements, and other properties that make human and other organism life possible.

Mercury, the planet closest to the Sun, has lesser mass and volume than the Earth, at a fraction of only 1/18. However, it is as dense as the Earth, although Mercury's surface is made up of more solid mass, specifically rough, porous, dark-colored rocks. Its atmosphere is made up of sodium and potassium, which accounts for the planet's density and very thin atmosphere. It was hypothesized that the core of Mercury is made up of liquid iron compound, as a result of the presence of magnetic field.

Venus, meanwhile, exhibits a unique characteristic for being the brightest and hottest planet in the sky, with the presence of sulfur in the clouds and with a temperature of 460°C. Apart from sulfuric acid in the clouds, the planet's atmosphere is also composed of carbon dioxide. Because of its the large percentage of carbon dioxide, scientists assumed that what little water contained in Venus were evaporated and condensed into its clouds, without precipitation, using up all water resources it has. Thus, life in Venus is not possible because of the lack of oxygen and water in it.

Among the planets, it is Mars that has been found to have potential to support human life because of its numerous similarities with Earth in terms of its properties. The planet has 1/3 of the Earth's surface, which is estimated to be as large only...

It is characterized by its predominantly cold weather, with the presence of ice caps in its surface, and dust storms during times of "summer" and "spring" (when Mars is closes to the Sun). It was also believed that Mars' interior is also composed of the crust, mantle, and core. Though it was not determined whether the composition of each interior layer is similar to Earth's, it is hypothesized to have a core mainly made up of iron and nickel. However, in contrast to the Earth, the Mars did not have plate tectonics, making its surface a solid piece of mass. Its atmosphere is mainly made up of carbon dioxide, nitrogen, and argon, with trace amounts of oxygen, carbon monoxide, and water vapor.
Other planets farther from the Sun and relatively far from the Earth are Jupiter, Saturn, Uranus, Neptune, and Pluto. These planets are known for their gaseous surfaces, as compared to the more solid surfaces of Mercury, Earth, Venus, and Mars. Jupiter is composed of a dense ball of ammonia and ice crystals, while its surface is made up of molten rock and iron. Saturn, with its planetary rings, has both hydrogen gas and liquid (which becomes metallic hydrogen) for its atmosphere and interior, respectively. Uranus has an atmosphere composed of hydrogen, helium, and methane, while its surface interior is made up of frozen water and rock. Neptune, the last of the known Jovian planets, shares similar characteristics as Uranus, composed primarily of hydrogen, helium, methane, frozen water and rock. Pluto, the last known planet in the solar system, is also composed of gaseous components, mainly that of methane, nitrogen, and ethane.