Planetary Society logo
  • “Exploration is in our nature.” - Carl Sagan

Scale comparisons of the solar system's major moons

Emily Lakdawalla

Written by Emily Lakdawalla
July 10, 2013

Here's a presentation slide I've been meaning to put together for a while. It shows the major moons of the eight planets, to scale with each other. Below is a labeled version. You can download one without text here, and if you scroll down I've got a couple of alternative layouts.

Note: it's been pointed out to me that the Callisto image is from Voyager, not Galileo. I'll fix the text on the image eventually. --ESL

The Solar System's Major Moons
The Solar System's Major Moons The Solar System contains 18 or 19 natural satellites of planets that are large enough for self-gravity to make them round. (Why the uncertain number? Neptune’s moon Proteus is on the edge.) They are shown here to scale with each other. Two of them are larger than Mercury; seven are larger than Pluto and Eris. If they were not orbiting planets, many of these worlds would be called “planets,” and scientists who study them are called “planetary scientists.”Image: NASA / JPL-Caltech / Montage by Emily Lakdawalla. The Moon: Gari Arrillaga. Processing by Ted Stryk, Gordan Ugarkovic, Emily Lakdawalla, and Jason Perry.

Here are some alternative unlabeled versions:

The Solar System's Major Moons (sorted by location)
The Solar System's Major Moons (sorted by location) Image: Montage by Emily Lakdawalla. The Moon: Gari Arrillaga. Other moons data: NASA/JPL. Processing by Ted Stryk, Gordan Ugarkovic, Emily Lakdawalla, and Jason Perry.
The Solar System's Major Moons (scattered)
The Solar System's Major Moons (scattered) Image: Montage by Emily Lakdawalla. The Moon: Gari Arrillaga. Other moons data: NASA/JPL. Processing by Ted Stryk, Gordan Ugarkovic, Emily Lakdawalla, and Jason Perry.

For the next one, I used a different Iapetus image, because it's adjacent to the Uranian moons Oberon and Ariel for which we don't have good lower-phase (fuller) global views; putting in the higher-phase one I used above made it look too big. Ganymede looks a little small for the same reason, and also because Titan's atmosphere makes it look bigger than it actually is.

The Solar System's Major Moons (ordered by size)
The Solar System's Major Moons (ordered by size) Image: Montage by Emily Lakdawalla. The Moon: Gari Arrillaga. Other moons data: NASA/JPL. Processing by Ted Stryk, Gordan Ugarkovic, Emily Lakdawalla, and Jason Perry.

Take a Stand for Our Future in Space

Take action for space exploration! Give today to have your gift matched up to $75,000.

Donate