Mariner 10

Spacecraft· NASAinactive

Mariner 10 — the first spacecraft to visit Mercury (three flybys, 1974–1975) and the first to use a gravity assist (at Venus).

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Key facts

Distance from Sun

0.317 AU

Status

Completed

Launched

1973

Mission & specifications

Mission

Operator: NASA
Launched: November 3, 1973
Status: Completed

Trajectory

Distance from the Sun: 0.317 AU
Distance from Earth: 1.29 AU
Distance from Mercury: 6,616 km

Mission

Mariner 10 was a mission of firsts. Launched on 3 November 1973, it became the first spacecraft to visit the planet Mercury and the first to use the gravity of one planet to reach another. To get to Mercury — a difficult target, deep in the Sun's gravity well — it first flew past Venus in February 1974, letting the planet's gravity bend and slow its path in a manoeuvre, now routine, that had never been tried before. The trajectory looped Mariner 10 past Mercury not once but three times, in March and September 1974 and March 1975, as spacecraft and planet returned to the same meeting point. It photographed nearly half of Mercury's surface, revealing a heavily cratered, Moon-like world dominated by the huge Caloris impact basin. Its most surprising discovery was that Mercury, despite being small and slow-rotating, has a global magnetic field — implying a large iron core and a partly molten interior. The same battered hemisphere faced the spacecraft at each encounter, so half of Mercury stayed unseen. After exhausting the gas it used to point itself, Mariner 10 was switched off on 24 March 1975. It remained our only close look at Mercury until MESSENGER arrived more than thirty years later.

1973Launch toward Venus and MercuryLaunch
Sets out on the first mission to use one planet's gravity to reach another.
1974Venus gravity assistFlyby
The first gravity-assist flyby, bending the trajectory inward toward Mercury.
1974First Mercury flybyFlyby
First spacecraft at Mercury; images a cratered, Moon-like world and the huge Caloris basin.
1974Mercury's magnetic field foundMilestone
Detects an unexpected global magnetic field, implying a large iron core.
1975Third and closest Mercury flybyFlyby
A final pass returns the highest-resolution images of the same sunlit hemisphere.
1975Out of attitude gasMission end
With its pointing gas exhausted, Mariner 10 is switched off — our last look at Mercury for 33 years.

Images

Mercury: Beethoven Quadrangle, H-7 — NASA/JPL · NASA Image Library

Mercury Southern Hemisphere — NASA/JPL · NASA Image Library

MESSENGER First Look at Mercury Previously Unseen Side — NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington · NASA Image Library

Incoming Hemisphere - Enhanced Color — NASA/JPL/Northwestern University · NASA Image Library

Mercury: Photomosaic of the Shakespeare Quadrangle Northern Half H-3 — NASA/JPL · NASA Image Library

High Resolution View of Mercury — NASA/JPL · NASA Image Library

Hilly and Lineated Terrain — NASA/JPL/Northwestern University · NASA Image Library

Large Mercurian Crater — NASA/JPL/Northwestern University · NASA Image Library

Images from open archives · credit shown per image