Sucks to be a moon

Interesting stuff that I’ve learned today: Mercury (4880Km in diameter) is smaller than Saturn’s moon Titan (5120-5150Km), and Jupiter’s Ganymede (5262Km). Yet, Mercury’s a planet, while the others are not. Of course, Mercury’s not orbiting a BA planet.

Mercury, Titan and Ganymede

Entire truth be told, Titan and Ganymede altogether weigh less than Mercury, for their densities are about half of the latter’s - Titan’s mass is about 1.3452 * 10^23 Kg, Ganymede’s mass is about 1.4819 * 10^23 Kg, while Mercury’s is somewhere around 3.302 * 10^23 Kg. Numbers are from Wikipedia and some other sources, but they’re pretty close to reality.

Here’s a nice image from kokogiak.com which portrays the known bodies of the solar system relative to their (again) known sizes: