Explore / The solar system

Meet the planets.

Four rocky worlds. Two gas giants. Two ice giants. Travel outward from the Sun and find out what makes each one different.

01Rocky planet

1 from the Sun

Mercury

The smallest planet takes the shortest trip around the Sun.

Its rocky surface is covered in craters. With almost no atmosphere to hold heat, the difference between day and night is extreme. A short year does not mean a short day: Mercury rotates very slowly.

Mean diameter: 4,879 km
Average Sun distance: 58 million km
One year: 88 Earth days

01Connect the science to play

These games use imaginary planets and playful mechanics. Use them as a conversation starter, then compare the real measurements.

Compare Mercury ✦NASA facts ✦

02Rocky planet

2 from the Sun

Venus

Earth’s near-size neighbor is wrapped in a thick atmosphere.

Venus is hotter than Mercury despite being farther from the Sun. Its dense atmosphere traps heat. It also spins in the opposite direction to most planets, and one rotation takes longer than its year.

Mean diameter: 12,104 km
Average Sun distance: 108 million km
One year: 224.7 Earth days

01Connect the science to play

These games use imaginary planets and playful mechanics. Use them as a conversation starter, then compare the real measurements.

Compare Venus ✦NASA facts ✦

03Rocky planet

3 from the Sun

Earth

Our ocean-covered home is the starting point for every comparison.

Earth has liquid water on its surface and an atmosphere that supports life. Its single natural moon is a familiar companion. Comparing other worlds with Earth helps turn very large numbers into something easier to picture.

Mean diameter: 12,742 km
Average Sun distance: 150 million km
One year: 365.3 Earth days

01Connect the science to play

These games use imaginary planets and playful mechanics. Use them as a conversation starter, then compare the real measurements.

Compare Earth ✦NASA facts ✦

04Rocky planet

4 from the Sun

Mars

A rusty desert world with a day surprisingly close to ours.

Iron minerals give Mars its red appearance. It has polar ice, enormous volcanoes, and a thin atmosphere. Its rotation is similar to Earth’s, but a full orbit takes almost twice as long.

Mean diameter: 6,779 km
Average Sun distance: 228 million km
One year: 687 Earth days

01Connect the science to play

These games use imaginary planets and playful mechanics. Use them as a conversation starter, then compare the real measurements.

Compare Mars ✦NASA facts ✦

05Gas giant

5 from the Sun

Jupiter

The largest planet is a fast-spinning world of clouds and storms.

Jupiter has no solid surface like Earth’s. Bands of clouds circle the planet, and its Great Red Spot is a long-lived storm. Even with its huge size, Jupiter completes a rotation in roughly ten hours.

Mean diameter: 139,822 km
Average Sun distance: 778 million km
One year: 4,332.8 Earth days

01Connect the science to play

These games use imaginary planets and playful mechanics. Use them as a conversation starter, then compare the real measurements.

Compare Jupiter ✦NASA facts ✦

06Gas giant

6 from the Sun

Saturn

A gas giant surrounded by a spectacular system of icy rings.

Saturn’s rings are made of many pieces of ice and rock, rather than one solid band. The planet is the second largest in the solar system. Our size comparison measures the planet itself and excludes its rings.

Mean diameter: 116,464 km
Average Sun distance: 1,400 million km
One year: 10,755.7 Earth days

01Connect the science to play

These games use imaginary planets and playful mechanics. Use them as a conversation starter, then compare the real measurements.

Compare Saturn ✦NASA facts ✦

07Ice giant

7 from the Sun

Uranus

A pale ice giant that rolls through its orbit on its side.

Uranus has an extreme axial tilt, making its seasons very different from Earth’s. Methane in its atmosphere contributes to its blue-green appearance. It belongs to the ice giants, a different planetary family from Jupiter and Saturn.

Mean diameter: 50,724 km
Average Sun distance: 2,900 million km
One year: 30,687.2 Earth days

01Connect the science to play

These games use imaginary planets and playful mechanics. Use them as a conversation starter, then compare the real measurements.

Compare Uranus ✦NASA facts ✦

08Ice giant

8 from the Sun

Neptune

The most distant planet takes about 165 Earth years to orbit the Sun.

Neptune is a cold, windy ice giant. Sunlight takes about four hours to reach it. Its long orbital period is a reminder that the outer solar system runs on a very different timescale from our own.

Mean diameter: 49,244 km
Average Sun distance: 4,500 million km
One year: 60,190 Earth days

01Connect the science to play

These games use imaginary planets and playful mechanics. Use them as a conversation starter, then compare the real measurements.

Compare Neptune ✦NASA facts ✦

A few things to keep in mind

01Why isn’t Pluto one of the eight?

Pluto is classified as a dwarf planet. Our guide focuses on the eight planets, while NASA’s dwarf planet guide explains the other worlds in that family.

02Can a day be longer than a year?

Yes, if by “day” you mean one complete rotation. Venus takes longer to spin once relative to the stars than it takes to orbit the Sun. A sunrise-to-sunrise solar day is a different measurement.

Sources & measurement notes

Mean radii and orbital periods: NASA/JPL planetary physical parameters. Diameter is twice mean radius. Average Sun distances and rotation durations are rounded from NASA’s planet guides. Distances vary along each orbit; these values are not live positions or distances from Earth.

Explore each source: Mercury · Venus · Earth · Mars · Jupiter · Saturn · Uranus · Neptune.

Compiled September 10, 2026. Illustrations are stylized, not telescope images. This site is independent and is not affiliated with NASA.