Mariner Exploration Missions

The Mariner series of U.S. spacecraft explored the inner solar system, obtaining information about Mercury, Venus, and Mars. Mariner 2 was the first successful space probe and the first spacecraft to visit a planet. It passed Venus at about 34,758 km on December 14, 1962. Mariner 4 explored Mars at low resolution in 1965 and Mariners 6 & 7 got a higher resolution look in 1969. Mariner 9 mapped entire surface of Mars in 1971 and 1972, sending back 7329 closeup pictures. Mariner 9 arrived into martian orbit on November 13, 1971 in the midst of an enormous dust storm which completely obscured the surface for weeks. When the dust cleared it found such remarkable features as a 24km (15 mile) high volcano named Olympus Mons, three times as high as Mt. Everest. Mariner 10 mapped surface of Mercury in 1974 as a part of a fortuitous slingshot orbit with Venus.

Mariner 2

Mariner 2 was the first successful space probe and the first spacecraft to visit a planet. It collected data for three months, passing Venus at about 34,758 km on December 14, 1962.

Mariner 2 discovered the solar wind, the flux of charged particles escaping the Sun at supersonic speeds.

The onboard magnetometer failed to measure a magnetic field for Venus, which was surprising since Venus must be similar in composition to the Earth. Venus has specific gravity 5.24 compared to the Earth's 5.5, so it must also have an iron core. The rotation period of Venus is 243 days, so it is apparently not fast enough to drive the dynamo effect which is credited with producing the Earth's magnetic field.

Mariner 9

A member of the extended Mariner series, Mariner 9 mapped entire surface of Mars in 1971 and 1972, sending back 7329 closeup pictures. Mariner 9 arrived into martian orbit on November 13, 1971 in the midst of an enormous dust storm which completely obscured the surface for weeks. When the dust cleared it found such remarkable features as a 24km (15 mile) high volcano named Olympus Mons, three times as high as Mt. Everest.

In retrospect, the massive dust storm did a great service for humanity. It was observed that the surface temperature of Mars dropped precipitously during the dust storm. At the time there was great debate about what the detonation of nuclear weapons would do to the Earth, and it was realized that nuclear weapons would put enormous clouds of dust into the atmosphere. The dust storm helped to make clear that a nuclear weapons exchange would drop the Earth's surface temperature in a scenario that came to be called "Nuclear Winter". These considerations undoubtedly helped in the process of nuclear weapons control.

The resolution of Mariner 9's images was about 1 km.

Mariner 10 Slingshots

When Mariner 10 passed by Venus on February 5, 1974 at a distance of 5770 km, it gained energy from the collision in what is called a slingshot maneuver. This was a particularly favorable maneuver, because the project directors discovered that the orbit could be fine tuned to loop around Mercury and back to Venus in twice Mercury's orbital period, so that it could loop back to look at Mercury again every second orbit. So instead of one look at Mercury, the Mariner craft got three flybys before its fuel ran out.