Ganymede is a moon of Jupiter and the largest moon in the Solar System. Completing an orbit in roughly seven days, it is the seventh moon and third Galilean moon from Jupiter. Ganymede participates in a 1:2:4 orbital resonance with the moons Europa and Io, respectively. It is larger in diameter than the planet Mercury but has only about half its mass. It has the highest mass of all planetary satellites with 2.01 times the mass of the Earth's moon. It is composed primarily of silicate rock and water ice, and a saltwater ocean is believed to exist nearly 200 km below Ganymede's surface. Ganymede is the only satellite in the Solar System known to possess a magnetosphere, likely created through convection within the liquid iron core. The satellite has a thin oxygen atmosphere that includes O, O2, and possibly O3. Ganymede's discovery is credited to Galileo Galilei, who observed it in 1610. The satellite's name was soon suggested by astronomer Simon Marius, for the mythological Ganymede, cupbearer of the Greek gods and Zeus's beloved.

Read the rest of this article: http://en.wikipedia.org/wiki/Ganymede_%28moon%29

_______________________________ Today's selected anniversaries:

532:

The Nika riots began in Constantinople, resulting in nearly half the city being burned or destroyed and tens of thousands of people being killed. http://en.wikipedia.org/wiki/Nika_riots

1842:

When he reached the safety of a garrison in Jalalabad, Afghanistan, William Brydon, an assistant surgeon in the British Army during the First Anglo-Afghan War, became the sole European survivor of a party of over 4,500 military personnel and over 10,000 civilian camp followers retreating from Kabul, excluding a few prisoners released later. http://en.wikipedia.org/wiki/William_Brydon

1898:

The Paris newspaper L'Aurore published "J'accuse...!", an open letter by French writer Émile Zola to French President Félix Faure exposing the Dreyfus affair. http://en.wikipedia.org/wiki/J%27accuse_%28letter%29

1968:

American singer Johnny Cash recorded his landmark album At Folsom Prison live at the Folsom State Prison in Folsom, California. http://en.wikipedia.org/wiki/At_Folsom_Prison

1991:

The January Events: Soviet troops attacked Lithuanian independence supporters at the TV Tower in Vilnius, killing 14 people. http://en.wikipedia.org/wiki/January_Events

_____________________________ Wiktionary's word of the day:

go the extra mile (v): (idiomatic) To make an extra effort; to do a particularly good job http://en.wiktionary.org/wiki/go_the_extra_mile

___________________________ Wikiquote quote of the day:

All religions speak about death during this life on earth. Death must come before rebirth. But what must die? False confidence in one’s own knowledge, self-love and egoism. Our egoism must be broken. --G. I. Gurdjieff http://en.wikiquote.org/wiki/G._I._Gurdjieff