Mariner 7

Mariner 7

Spacecraft· NASA / JPLcompleted

Mariner 7 — Mariner 6's identical twin (Mars flyby 5 August 1969). Days before arrival its signal briefly vanished — most likely a venting battery that nudged its course — before controllers recovered it. It returned 126 images, the most of any Mars mission to that point, including a full-disk view revealing the bright spot later known as the giant volcano Olympus Mons.

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Key facts

Distance from Sun
1.51 AU
Status
Completed
Launched
1969

Mission & specifications

Mission

Operator
NASA / JPL
Launched
March 27, 1969
Status
Completed

Trajectory

Distance from the Sun
1.51 AU
Distance from Earth
1.89 AU
Distance from Mars
1,815,068 km

Mission

Mariner 7 was Mariner 6's identical twin, and it very nearly did not survive to reach Mars. Launched on 27 March 1969, it was closing on the planet when, days before the encounter, its signal abruptly vanished — most likely because its silver-zinc battery vented or ruptured, nudging the spacecraft off course. Controllers scrambled, switched it to a backup antenna, recovered contact, and re-computed its aim in time. On 5 August 1969 it flew past Mars at about 3,430 kilometres and returned 126 images — more than any Mars mission before it — including close views of the south polar cap and the smooth Hellas basin, a glimpse of the tiny moon Phobos, and a famous full-disc portrait in which a single bright spot stood out. That spot, then catalogued as Nix Olympica, would later be recognised as Olympus Mons, the largest volcano in the solar system — a hint, hidden in the data, of how much the twin flybys had still left to discover.

  1. 1969The identical twinLaunch

    Mariner 6's twin launches on an Atlas-Centaur toward Mars.

  2. 1969Anomaly and recoveryMilestone

    Its signal vanishes days before arrival — likely a venting battery that shifts its course — before controllers recover it.

  3. 1969Mars flybyFlyby

    Returns 126 images — the most yet — including a full disc showing Nix Olympica, later known as Olympus Mons.

  4. 1971Tracking endsMission end

    Ends its days in heliocentric orbit; tracking continued into 1970–71 (exact end uncertain).

Images

Mars on approach, imaged by Mariner 7 in August 1969 — the bright spot is Nix Olympica, now known as the volcano Olympus Mons
NASA / JPL (public domain) · Wikimedia Commons

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