## Size of the Planets

by Abby Cessna[/caption]

It is often difficult to grasp just how large the planets actually are. There are a number of ways to measure a planet, including diameter, volume, and surface area.

Mercury is the smallest planet in our Solar System since Pluto was demoted to a dwarf planet. It has a diameter of 4,879 km, and a surface area of 17.48 x 10^{7} km^{2}, which is only about 11% of Earth’s surface area. Mercury’s volume is even smaller in comparison at 6.083 x 10^{10 }km^{3}, which is only 5.4% the volume of Earth.

Venus is similar in size to Earth, which earned it the title of Earth’s twin. Venus has a diameter of 12,100 km and a surface area of 4.6 x 10^{8} km^{2}. These measurements are 95% and 90% of Earth’s diameter and surface area respectively. With a volume of 9.38 x 10^{11} km^{3}, Venus’ volume is 86% of Earth’s.

Earth has a diameter of 12,742 km and a surface area of 5.1 x 10^{8} km^{2}. Its volume of 1.08 x 10^{12 }km^{3} gives the planet the largest volume of any of the terrestrial planets.

Mars is also a small planet, the second smallest in our Solar System. Mars’ diameter is 6,792 km, only about 53% of Earth’s diameter. At only 28% of Earth’s surface area, Mars has a very small surface area of 1.45 x 10^{8 }km^{2}. Mars’ volume of 1.63 x 10^{11} km^{3} is only 15% of Earth’s volume.

All of the gas giants are larger in size than the four inner planets. Jupiter is the largest planet in our Solar System. It has a diameter of 143,000 km, which is more than 11 times the size of Earth’s diameter. The numbers only get larger from there. Jupiter has a surface area of 6.22 x 10^{10} km^{2}. That is 122 times greater than Earth’s surface area. Jupiter’s volume of 1.43 x 10^{15} km^{3} is an incredible number. You can fit 1321 Earths inside Jupiter.

Saturn is the second largest planet in our Solar System. It has a diameter of 120,536 km across the equator, and a surface area of 4.27 x 10^{10} km^{2}. With a volume of 8.27 x 10^{14} km^{3}, Saturn can hold 764 Earths inside.

Uranus has a diameter of 51,118 km and a surface area of 8.1 x 10^{9} km^{2}. Although Uranus is much smaller than Jupiter, it is still large. With a volume of 6.83 x 10^{13} km^{3}, you could fit 63 Earths inside the gas giant.

Neptune is slightly smaller than Uranus, but still very large. The planet has a diameter of 49,500 km. You could fit 57.7 Earths inside Neptune, which has a volume of 6.25 x10^{13} km^{3}. Neptune has a surface area of 7.64 x 10^{9} km^{2}, which is 15 times Earth’s surface area.

the mass of the planets and atmosphere of the planets.

For more information, check out this website to learn all about the planets and this page from NASA to learn about the planets.

Astronomy Cast has an episode on each of the planets including Mercury.

Earth, Jupiter, Mars, Mercury, Neptune, Saturn, size of the planets, Uranus, Venus

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