Mariner 10 was launched at Cape Canaveral on November 3, 1973, at 5:45 UTC. The launch vehicle was an Atlas-Centaur 34. Its mass was 1108.704 pounds. This mass included 176 pounds of scientific payload and 44 pounds of hydrazine fuel. The scientific payload included a television system, IR radiometer, UV airglow and occultation spectrometers, a radio science and celestial mechanics package, magnetometer, a charged particle telescope and a plasma analyzer.
The rocket engine consisted of 222-N liquid mono propellant hydrazine.
The seventh successful mission of the Mariner series cost $100 million. It gave the first close-range measurements of Venus in 1974. It also used the gravitational field of Venus to assist it in reaching Mercury, also a first.
Mariner 10 photographed about 45% of the surface of the planet Mercury in three flybys. Mercury is the closest planet to the Sun. It was the first artificial satellite to visit Mercury.
In January 1974, Mariner 10 made ultraviolet tests of the comet Kohoutek. It arrived at the planet Venus on February 2, 1974, and found that Venus had a Hadley-type atmosphere. It also found a weak magnetic field and that the ionosphere interacted with the solar wind to cause a bow shock.
Mariner 10 made the three flybys of Mercury on March 29, 1974; September 21, 1974; and March 16, 1975. It found that Mercury does not have an atmosphere, and pictures taken of the surface revealed craters similar to the Moon. The mission ended on March 24, 1975.
During the first flyby of Mercury, Mariner 10 came as close as 434 miles from the planet's surface. A global magnetic field was discovered during this flyby. Several pictures were taken. The second flyby was 29,868 miles above Mercury at the closest. The altitude was much higher and the surface of Mercury had not changed much since the first flyby. The third flyby, however, was much more successful. It came the closest to Mercury of the three flybys at 203 miles above the surface of the planet.
The magnetic field discovered during the first flyby was measured on March 16, 1975. More pictures were taken of the planet's surface. Tests continued for a few days until, on March 24, 1975, the supply of attitude-control gas ran out.
The total cost of all 10 Mariner missions was $554 million. Mariner 10 encountered several problems, including flaking paint, unscheduled computer resets, and problems with the high-gain antenna.