Mariner 4: Arrived at Mars on July 14, 1965 and passed within 9,920 kilometers of the planet's surface. It returned 22 close-up photos showing a cratered surface. The thin atmosphere was confirmed to be composed of carbon dioxide in the range of 5-10 millibars. A small, intrinsic, magnetic field was detected. Mariner 4 is now in a solar orbit.

Mariner 6: Arrived at Mars on February 24, 1969, and passed within 3,437 kilometers of the planet's equatorial region. Mariner 6 took measurements of the surface and atmospheric temperature, surface molecular composition, and pressure of the atmosphere. In addition, over 200 pictures were taken. Mariner 6 is now in a solar orbit.

Mariner 7: Arrived at Mars on August 5, 1969, and passed within 3,551 kilometers of the planet's south pole region. Mariner 7 also took measurements of the surface and atmospheric temperature, surface molecular composition, and pressure of the atmosphere. In addition, over 200 pictures were taken. Mariner 7 is now in a solar orbit.