[X] My Assistant

[Cugel]

For a long time in history Titan has been considered to be the largest of all moons in our solar system. And rightfully so! Unfortunately, somebody got the crazy idea that the atmosphere of Titan does not count, and indeed, the diameter of the rocky/icy body of Titan is roughly 100 km. less in diameter than that of a pitiful piece of debris called Ganymede orbitting 'That Other Planet'.

So, what would be the biggest planet in the solar system if we don't count atmospheres anymore, huh? Probably not that 'That Other Planet'! It's ridiculous.

I think Titan should be back on the #1 spot of Greatest Moons. ASAP.

What do you think?

[Rob Pinnegar]

That's right. Titan was always thought to be a fair bit bigger than Ganymede. I guess that the thickness of the atmosphere was what threw astronomers off -- they thought the orange cloud layer was the surface and didn't realize that the true surface was much deeper down. An understandable mistake, really. Remember there was no Hubble telescope back then.

Even more poorly constrained was Triton's diameter. I distinctly remember that one of the astronomy books in my hometown library ("Solar System" by Ludek Pesek, maybe?) claimed that Triton's diameter could have been as large as 6000 km, making it the largest satellite in the Solar System. It is of course slightly less than half that size in reality. I guess the moon's albedo was drastically underestimated.

Now that I think of it though, it might also have been due to the same limit-of-resolution problem that caused Pluto's diameter to be listed as "3,600 miles" for decades. 3,600 miles is almost exactly 6000 kilometres.