USGS

Introduction to the Io source data

Io has now been visited by five spacecraft:

Mission

Closest encounter date(s)

Type of encounter

Significant Io discoveries

Closest approach (km)

Best image resolution

Pioneer 10

3 December 1973

flyby

  • ionosphere
  • mass discovered to be 23% greater than thought
  • no images

    no images

    Pioneer 11

    2 December 1974

    flyby

    young surface

    756,000

    357 km

    Voyager 1

    5 March 1979

    flyby

    active volanism on Io

    21,000

    1 km

    Voyager 2

    9 July 1979

    flyby

    changes on surface since Voyager 1 encounter

    1,130,000

    20 km

    Galileo

    7 December 1995 to

    31 December 1999

    Jupiter orbiter

    iron core

    245,000

    2.5 km

    The global geology map of Io is based on data from the Voyager 1 and Voyager 2 missions. See introductions in map texts for additional mapping source data information.


    To other data introductions: Mercury Venus Moon Mars Jovian Satellites: | Io | Europa | Ganymede | Callisto
    To index maps: Mercury Venus Moon Mars Jovian satellites: | Io | Europa | Ganymede | Callisto
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