The Space & Beyond Blog
Our solar system’s planets
A guide to our solar system’s eight planets
The planets of our solar system are fascinating worlds, divided into two categories: terrestrial and jovian. The terrestrial planets are small, rocky worlds and include Mercury, Venus, Earth and Mars. The jovian planets are gas giants and consist of Jupiter, Saturn, Uranus and Neptune. The order of the planets in our solar system, starting closest to the sun and working outward is: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Here is a short guide to our solar system’s planets and fun facts about them!
The innermost planet is the smallest in the solar system – it’s just a little larger than Earth’s Moon! It has such a high density that more than half of it must be made out of iron and nickel. The planet’s surface shows lots of craters, most dating from the age of heavy bombardment that characterized the solar system about 4 billion years ago. On Mercury, you would either freeze or roast; the highest surface temperature is 870° F, while the lowest temperature is -300° F.
Of all the planets, Venus most resembles Earth. The two have nearly the same size and density; however, Venus’ surface bakes at a temperature of 800° Fahrenheit. Its massive atmosphere of carbon dioxide traps solar radiation and creates a runaway greenhouse effect. Venus is the brightest object in the sky after the Sun and Moon, and is covered with craters, mountains, volcanos and lava plains.
Our home planet is about 93 million miles from the Sun. It goes around the Sun in 365 and ¼ days; every four years, the extra quarters add up to one whole day and we add a day to the end of February, creating a leap year. From space, Earth looks like the blue water world it is. About 70 percent of Earth’s surface is covered with water, and 97 percent of that water is in the salty oceans. The highest point on Earth’s surface is Mount Everest on the border of Nepal and China, at 29,035 feet.
Mars has long fascinated humans, largely because its surface can be seen clearly from Earth. Spacecraft and rover missions have revealed a nuanced world, where craters share space with massive (albeit extinct) volcanoes, giant canyons and dry channels. There’s little doubt that liquid water once existed on the martian surface, and many wonder if life might have followed! Rust in the soil creates the Red Planet’s signature color. The lowest surface temperature on Mars is -190° F, while the hottest temperature is 90° F.
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Jupiter is the largest planet in our solar system, with a diameter of 89,000 miles. Eleven Earths would fit side by side across the face of it! It takes Jupiter 12 Earth years to go around the Sun once, but only takes 10 hours to spin on its axis one time. Jupiter’s atmosphere is mostly made of hydrogen and helium, and the colorful cloud bands we see are actually cloud layers. The Great Red Spot on Jupiter is a gigantic storm that’s been around for almost 400 years. The average temperature at the top of Jupiter’s clouds is -244° F.
Saturn is the second-largest planet in the solar system, with a diameter of 74,900 kilometers. It does not have a solid surface and the atmosphere is mostly made of hydrogen and helium, like Jupiter. Saturn also has beautiful bands like Jupiter, but they are hidden by haze and smog. The average temperature on Saturn is -300° F. Saturn’s ring system is the largest of all the planets and are made of ice and rock particles – some as big as a minivan!
Uranus is the third-largest planet in the solar system. About four Earths would fit side-by-side across its face. Uranus has an average temperature of -350° F and does not have a solid surface. The planet goes around the Sun once every 84 Earth years.
Neptune is slightly smaller than Uranus and orbits at a distance of 2.8 billion miles, 30 times farther than Earth. Like other gas-giant planets, Neptune’s “surface” is the top of its deep atmosphere. This contains hydrogen, helium and methane, giving the planet its blue color. Six narrow rings encircle Neptune. Because some places have more particles than others, Neptune’s rings form arcs around the planet. The average temperature is -370° F.