Mariner 4 (together with Mariner 3 known as Mariner-Mars 1964) was the fourth in a series of spacecraft, launched on November 28, 1964, intended for planetary exploration in a flyby mode and performed the first successful flyby of the planet Mars, returning the first pictures of the Martian surface. It captured the first images of another planet ever returned from deep space; their depiction of a cratered, seemingly dead world largely changed the view of the scientific community on life on Mars. Mariner 4 was designed to conduct closeup scientific observations of Mars and to transmit these observations to Earth. Other mission objectives were to perform field and particle measurements in interplanetary space in the vicinity of Mars and to provide experience in and knowledge of the engineering capabilities for interplanetary flights of long duration. On December 21, 1967 communications with Mariner 4 were terminated.

The Mariner 4 spacecraft consisted of an octagonal magnesium frame, 1270 mm across a diagonal and 457 mm high. Four solar panels were attached to the top of the frame with an end-to-end span of 6.88 meters, including solar pressure vanes which extended from the ends. A 1,168 mm diameter high-gain parabolic antenna was mounted at the top of the frame as well. An omnidirectional low-gain antenna was mounted on a seven foot, four inch (2235 mm) tall mast next to the high-gain antenna. The overall height of the spacecraft was 2.89 meters. The octagonal frame housed the electronic equipment, cabling, midcourse propulsion system, and attitude control gas supplies and regulators.

A sailor, mariner, or seaman is a person who navigates water-borne vessels or assists in their operation, maintenance, or service. The term can apply to professional mariners, military personnel, and recreational sailors as well as a plethora of other uses. Etymologically, the name preserves the memory of the time when ships were commonly powered by sails, but it applies to the personnel of all vessels, whatever their mode of locomotion.

Professioners have left the industry and led noteworthy lives in the naval services or on the shore. For example, Traian Băsescu started his career as a third mate in 1976 and is now the President of Romania. Arthur Phillip joined the Merchant Navy in 1751 and 37 years later founded Sydney, Australia. Merchant mariner Douglass North went from seaman to navigator to winning the 1993 Nobel Prize in Economics.

Seafarers hold a variety of professions and ranks, each of which carries unique responsibilities which are integral to the successful operation of an ocean-going vessel. A ship's crew can generally be divided into four main categories: the deck department, the engineering department, the steward's department, and other.