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Ganymede Ganymede
Orbital characteristics
Orbital period 3.58 Terran days

4.929 Ganymedean days

Orbital axis
3,210,985 km
3,229,390 km
3,192,570 km
Physical characteristics
Rotation period
17.43 hours
8.71 hours
Mean diameter 19914 km
Surface area
1,245,900,000 km²
1,029,300,000 km² (83%)
216,600,000 km² (17%)

238 K
277 K
310 K
Atmospheric pressure (at MSL) 1145 mbar
24 (as of 2005)
Countries none recognized (according to UN)

Ganymede is the most massive planet of Jupiter. It supports life, and humans have settled there successfully.

Physical characteristics[]

Ganymede has relatively little iron, and most of it is in the core. Mantle and crust are mainly silicates. The planet supports extensive volcanism and plate tectonics.

Most of the surface is ocean, of which parts are frozen. There are few continents.

The deepest place is 18 940 meters deep and the tallest mountain is 9 480 meters high.


There are four continents on Ganymede:

Lincolnia is the biggest continent. It is about 100 million km². Three of four current settlements lie there.

Gandhia is a long but thin continent near the equator, having a surface area of little over 45 million km².

Tsetungia is a mountainous continent in eastern hemisphere. It has a surface area of little over 25 million km².

Southern continent is fully glaciated. It is about 25 million km² in extent.

Tectonic plates[]

Lincolnia is composed of West Lincolnian Plate and East Lincolnian Plate. West Lincolnian Plate is slowly moving under its eastern companion, creating the Honzu Plateau.

Gandhia is composed of Gandhian Plate. Its northwestern mountains are a result of interactions with the oceanic Meridian Plate.

Tsetungia is composed of the mountains, which are created by the Xiaoping and Zeming plates. The plates are mostly underwater, but they have few bulges, which show up as large islands (notably Nation Island and New Hainan on Xiaoping Plate, Nikolay Island and New Sahalin on Zeming Plate.

Southern Continent is only one plate.

Several plates are fully underwater. Notable example of their interactions is the subduction of Meridian Plate by Xiaoping Plate, which has created Trench of Our Lady of Guadalupe, with depth up to 18,940 meters.


Because of the small size of the continents, there aren't many significant rivers. The UN-made list of rivers uses only temporary designations:

List of longest rivers:

  • E Lincolnia I, 5094 km
  • W Lincolnia I, 4530 km
  • E Lincolnia II, 2933 km
  • W Lincolnia II, 2805 km


  • oxygen: 28.2 %
  • silicon: 27.2 %
  • iron: 24.6 %
  • magnesium: 15.9 %
  • nickel: 1.6 %
  • calcium: 1.8 %
  • aluminium: 1.5 %
  • sulfur: 0.70 %
  • sodium: 0.25 %
  • carbon: 0.2 %
  • boron: 0.1 %
  • titanium: 0.071 %
  • potassium: 0.019  %
  • other elements: 0.53 %


The climate on the planet is cold. Nevertheless, the difference in temperatures of main sea level and tropopause creates hurricanes. The winds are powerful also in other ways, due to fast rotation: The rotational speed on Ganymedean equator is over 3600 km/h, while on Earth it is only under 1700 km/h. It is worth noting, that this speed makes also Coriolis force stronger.

The coldest place is on the Southern Continent, at 89°S 142°W, with average temperatures: summer -63.8°C, winter -66.5°C.

The warmest place is on Lincolnia, at 4°N 121°W, with average temperatures: summer +16.4°C, winter +16.6°C. (This upside down situation results from the monsoon of summer)

The most rainy place is on Tsetungia, at 9°N 89°E, with average annual precipitation of 121 mm.


It is theorized, that around a billion years ago unicellular Terran life came to Ganymede, and multicellular organisms around 300 million years ago. Since then, the Ganymedean biosphere developed without animals, before 1949, when the Soviet Union did animal tests in Ganymede by unmanned spacecraft. Before 2005, the animal life of Ganymede consisted only of cats, dogs, bees, flies and monkeys.

Since the conquest of Venus there was a race to Ganymede. The first to land an unmanned spacecraft there was Soviet Union in 1948 and the first to send a man successfully to Ganymede was USA in 2004. The United States astronauts built a settlement there, migrating to Ganymede, sending samples only by an unmanned shuttle and information by radio.

Now there are four settlements on Ganymede: two American, one Chinese and one Japanese.


Because of Ganymedean relatively high atmospheric pressure, people often prefer being in 800-1200 metres above main sea level. The Earth-like atmospheric pressure is at 930 metres. The most liked place is Honzu Plateau, which lies 1000-2000 meters above MSL, near the equator.

The settlements:

  • Gateway Base, American government-owned, 2°N 103°W, 1296 m MSL (Honzu Plateau)
  • New Sacramento, owned by American civilians, declared independent, 12°N 97°W, 1060 m MSL (Honzu Plateau)
  • 木星京 (Wood Star Capital), PRC state-owned, 3°S 89°E, 1340 m MSL
  • Kawaiikyo (Cute Capital), Japan state-owned, 3°N 100°W, 1202 m MSL (Honzu Plateau)