March 26, 2026
The 8 Planets in Order: A Complete Guide
"My Very Educated Mother Just Served Us Nachos." That mnemonic has helped millions of students remember the planetary order since Pluto was reclassified in 2006. But memorizing the sequence is just the beginning. Each of the eight planets is a radically different world — from Mercury's 430-degree surface to Neptune's supersonic winds. Here's what NASA's data actually tells us about each one.
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Mercury: The Swift, Scarred Messenger
The closest planet to the Sun orbits at just 0.387 AU (57.9 million km) and completes one orbit every 88 Earth days. Mercury is tiny — its diameter of 4,879 km makes it only slightly larger than Earth's Moon (3,475 km). With virtually no atmosphere (surface pressure of about 10¹&sup5; times less than Earth's), temperatures swing wildly: up to 430°C on the sunlit side and down to -180°C at night.
NASA's MESSENGER spacecraft orbited Mercury from 2011 to 2015 and revealed water ice hiding in permanently shadowed craters near the poles — one of the most surprising discoveries in planetary science. Despite baking temperatures elsewhere, these craters haven't seen sunlight in billions of years.
Venus: Earth's Evil Twin
Venus is nearly identical to Earth in size (diameter 12,104 km vs. Earth's 12,756 km) and mass (81.5% of Earth's). But the similarities end there. A runaway greenhouse effect has turned Venus into the hottest planet in the solar system, with surface temperatures averaging 464°C — hot enough to melt lead. The atmosphere is 96.5% carbon dioxide at a crushing surface pressure of 9,200 kPa, equivalent to being 900 meters underwater on Earth.
Venus rotates backwards (retrograde) and so slowly that a single Venusian day lasts 243 Earth days — longer than its year of 225 days. The Soviet Venera program landed multiple probes on the surface in the 1970s and 80s; none survived longer than 127 minutes in the extreme heat and pressure.
Earth: The Goldilocks Planet
The third planet from the Sun sits at 1.0 AU, squarely in the habitable zone where liquid water can exist on the surface. Earth's mass of 5.972 × 10²&sup4; kg gives it enough gravity to hold a nitrogen-oxygen atmosphere, while its magnetic field — generated by a molten iron outer core — shields the surface from solar radiation. Of the eight planets, Earth is the densest at 5,514 kg/m³.
Earth is the only planet confirmed to support life, though that distinction may change as we explore ocean worlds like Europa and Enceladus. About 71% of Earth's surface is covered by water — a feature visible from space that gives our planet its distinctive blue appearance and its nickname, the Blue Marble.
Mars: The Red Planet
Mars orbits at 1.524 AU and is about half Earth's diameter (6,792 km). Its thin carbon dioxide atmosphere (surface pressure 0.636 kPa) can't retain heat, so temperatures range from -140°C at the poles to a relatively mild 20°C at the equator in summer. The red color comes from iron oxide (rust) in the surface soil.
Mars hosts the solar system's tallest volcano, Olympus Mons (21.9 km high, nearly 2.5 times the height of Everest), and its deepest canyon system, Valles Marineris (up to 7 km deep and 4,000 km long). Evidence from NASA's rovers and orbiters strongly suggests Mars once had flowing surface water, making it the primary target in the search for past microbial life.
Jupiter: King of the Planets
Jupiter is staggeringly large. Its equatorial diameter of 142,984 km means more than 1,300 Earths could fit inside it. Its mass — 1.898 × 10²&sup7; kg — is 2.5 times the mass of all other planets combined. Jupiter is a gas giant with no solid surface; its atmosphere of hydrogen and helium transitions gradually into a liquid interior under immense pressure.
The Great Red Spot, a storm larger than Earth, has been raging for at least 350 years. Jupiter's rapid rotation (9 hours 56 minutes per day) drives fierce winds and creates the banded cloud patterns visible through even modest telescopes. Jupiter has at least 95 known moons, including the four Galilean moons — Io, Europa, Ganymede, and Callisto — each a world unto itself.
Saturn: The Ringed Wonder
Saturn's magnificent ring system spans 282,000 km from edge to edge but averages only about 10 meters thick — a proportional thickness comparable to a sheet of paper stretched across a football field. The rings are composed primarily of water ice particles ranging from grains of sand to house-sized chunks. Saturn itself has a diameter of 120,536 km and is the least dense planet at 687 kg/m³ — less dense than water.
Saturn's moon Titan is the second-largest moon in the solar system and the only moon with a substantial atmosphere. Another moon, Enceladus, shoots geysers of water vapor from a subsurface ocean through cracks in its icy crust — making it one of the most promising places to search for extraterrestrial life.
Uranus and Neptune: The Ice Giants
Uranus and Neptune are classified as ice giants — distinct from the gas giants Jupiter and Saturn. Uranus, at 19.19 AU, has the coldest atmosphere of any planet (-224°C) and rotates on its side with an axial tilt of 97.8 degrees, likely the result of a massive ancient collision. Its diameter of 51,118 km and pale blue-green color (from methane in the atmosphere) give it a featureless appearance in most images.
Neptune, the outermost planet at 30.07 AU, is the windiest world in the solar system. Wind speeds on Neptune reach 2,100 km/h — faster than the speed of sound on Earth. Its vivid blue color comes from methane absorbing red light. Neptune has only been visited once, by Voyager 2 in 1989, which revealed a dynamic atmosphere and a large dark storm system. With a diameter of 49,528 km, Neptune is slightly smaller than Uranus but denser and more massive.
Try It Yourself
Can you put all eight planets in the correct order — by distance, size, mass, or temperature? In Planet Lineup, you'll sort the planets by different properties and discover that the order changes depending on what you're measuring.
Play Planet Lineup →Sources
- NASA Planetary Fact Sheet. "Planetary Physical Parameters." nssdc.gsfc.nasa.gov.
- NASA Jet Propulsion Laboratory. "Solar System Exploration: Planets." solarsystem.nasa.gov.
- International Astronomical Union. "IAU Resolution B5: Definition of a Planet." iau.org (2006).