Callisto Moon
Image showing Callisto's highly cratered surface, the lighter areas are ice.
  • Callisto is the second largest moon orbiting Jupiter and the third largest moon in the solar system.
  • It has a diameter of 2,985 miles (4,800 km), which is only 1% smaller than the planet Mercury.
  • Callisto is the 8th moon in distance from Jupiter and takes 17 days to make one complete orbit of the planet.
  • It orbits Jupiter at an average distance of 1,168,000 miles (1,880,000 km).
  • Due to its orbit being further away from Jupiter it is not under the same tidal heating influences as Io, Europa or Ganymede.
  • Despite the lack of internal heat generated by Jupiter's gravity it is still possible that Callisto could have a salty subsurface ocean.
  • Callisto orbits beyond Jupiter's main radiation belt making it one of more safer environments in the outer solar system to locate a future manned base.
  • Callisto is the most cratered object in the solar system and has the oldest landscape.
  • Callisto has the lowest density of any of the "Galilean Moons".
  • The moon was discovered in January 1610 by the Italian astronomer Galileo Galilei.

surface of callisto
Close up image of Callisto's surface taken by the NASA spacecraft Galileo.
Callisto's Surface
Callisto is rather bland in appearance compared to the other "Galilean Moons" with a landscape dominated almost entirely by craters. Its icy surface is around 4 billion years old with no significant geological changes in that time.
Callisto's Atmosphere
Callisto has an extremely thin atmosphere although unlike Europa and Ganymede it is composed primarily of carbon dioxide instead of oxygen. It is now known that all four of the Galilean Moons have some form of atmosphere.
Callisto's Temperature
The highest daytime temperature on Callisto is around -108C (-162 F). At night temperatures can reach an even more chilly -193C (-315 F).

Life on Callisto
Microbial life may exist in the ocean underneath Callisto's surface although the conditions may be less favorable than on Europa or Ganymede.
Origin of Name
Callisto is named after a nymph from Greek mythology who became a lover of Zeus.

Missions to Callisto
JUICE (JUpiter ICy moon Explorer)
juice probe Launch: 2022
Arrival: 2030
Agency: ESA (European Space Agency)
Summary: The JUICE probe will study the Jovian system, focusing on the icy moons of Europa, Callisto and Ganymede, investigating any potential habitable environments.
New Horizons
new horizons Launch: January 2006
Arrival: January 2007
Agency: NASA
Summary: Made a successful flyby of Callisto on its way to Pluto sending back new images of the moon.
galileo Launch: October 1989
Arrival: December 1995
Agency: NASA
Summary: Galileo made several flybys of Callisto sending back close up images of the moon. They revealed the strange icy peaks that populate Callisto's surface.
Voyager 1 and 2
Voyager 2 Launch: August-September 1977
Arrival: April-August 1979
Agency: NASA
Summary: Voyager 1 and 2 made successful flybys of Callisto providing an array of new data. It gave precise measurements of its temperature, shape and mass as well sending back high resolution images.
Pioneer 10 and 11
Pioneer 10 Launch: March 1972 - April 1973
Arrival: December 1973 - December 1974
Agency: NASA
Summary: Pioneer 10 and 11 made successful flybys of Callisto but provided little new information.

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