It was supposed of old that our Earthly moon, as its Latin name implies, might make men lunatics. Thus Othello's feeble excuse for killing Desdemona:
It is the very error of the moon;
She comes more near the Earth than she was wont
And drives men mad.
By this reckoning, Mercury and Venus are the sanest places in the solar system: neither planet has any moon at all. Martians, on the other hand, might be twice as mad as we are, since their planet has two moons, but their eccentricity might be tempered by the fact that Deimos and Phobos are only tiny things, each no bigger than an Aran island. Pluto is difficult to assess in this respect. It has only one moon, like Earth, but this one moon is comparable in size to the planet itself.
Charon would loom in the Plutan sky about six times larger than our Moon appears from Earth - which surely cannot be good for anybody's mental health. With the larger planets, the situation is even more complex, because it is difficult to say, at any given time, how many moons each planet has. Until comparatively recently, for example, Uranus had 15 moons. Titania and Oberon were noticed as early as 1787; then Ariel and Umbriel appeared in 1851; and Miranda almost a century later in 1948.
The other 10 - Ophelia, Cordelia, Juliet, Belinda, Portia, Rosalind, Puck, Bianca, Cressida and Desdemona - were all children of the space age. Then the discovery of Caliban, Sycorax , Prospero, Setebos and Stephano brought Uranus's total to 20, and the 21st, incongruously referred to as 1986U10, is so new that it has not yet received a name.
With these developments, Uranus had overtaken Saturn which was thought to have only 18 moons: Atlas, Prometheus, Pandora, Epimetheus, Janus, Mimas, Enceladus, Tethys, Telesto, Calypso, Dione, Helene, Rhea, Hyperion, Titan, Iapetus, Phoebe and Pan. But then just last October astronomers discovered four more Saturnian moons, bringing its total to 22, surpassing Uranus to put it in the lead again.
Saturn's lead, however, may not last too long. Jupiter at the last count had 16 named moons and a 17th discovered in 2000 provisionally called S/1999J1. But rumour has it that there are another 11 moons swirling around the planet just waiting for their labels.
So what is the sum of this celestial lunacy? If we reckon Neptune to have a constant eight moons, then the full inventory of known and suspected entities in our solar system comes to one star, nine planets and 83 moons.