Solid Bodies in the Solar System – a great map

Steph P. Bianchini January 3, 2015 11 Comments

That xkcd is an amazing website, you already know (and if you don’t, go and have a look at it now! You won’t regret it). But you often find out that some of its graphics are conceptually powerful – like this one putting together all the solid bodies of the Solar System in a old-style map.

(Credit: XKCD)

Our planet is, not surprisingly, the biggest one – we’re talking about rocky ones, remember: so no gas or ice giants will show up in this list – with Venus, the smaller twin of Earth, a close second. Ganymede, the biggest moon of Jupiter with its 3,280 miles of diameter, is bigger than Mercury and almost the size of Mars. Our Moon, while smaller than others, still presents a respectable size, especially when compared in size to the Earth (this has made scientists come out with a series of hypotheses regarding its formation). Other moons are equally impressive for other reasons, like the beautiful Titan (another big chunk in the map) or the strange Miranda (see this article for some pretty images and other info about them).

(Credit: NASA/JPL )

In the lower part of the map there’s a sort of “residual” region, which put together all the rest of solid stuff in the System, like smaller moons, comets and so on. And some of the smaller moons can be really small: not only big moons can have their own moonlet (and smash them too, like Iapetus that might have used its own to create its mountains) but also small bodies themselves like asteroids can have them. An example? The 20-mile wide asteroid Ida, orbited by its one-mile wide moon, Dactyl – so minuscule that only the Galileo spacecraft, flying at a close 6,500 miles from it, was able to discover in 1993.

(Credit: Iceagenow.com)

Some other statistics might be interesting as well. The Sun accounts alone for 99% of the mass in our Solar System. Of the remaining bodies, Jupiter is by far the biggest one (its radius is 1/10 the one of the Sun) – a giant in its own right, and containing about 1,321 Earth. Apparently, it has swallowed up a smaller rival in the course of its evolution, and this would explain its size.

Just a final note: New Horizons will reach Pluto later this year, and on July 2015 it will be at the closest distance from this tiny, frozen celestial object. I put emphasis on tiny – have a look at the map: Pluto’s diameter is only 1400 miles, about half of the distance between California to Maine. But I won’t suggest you to go there for a drive.