The Complete Book of Spaceflight: From Apollo 1 to Zero Gravity

An early series of NASA interplanetary probes
developed and operated by JPL (Jet Propulsion
Laboratory). The Mariners became the first probes to
return significant data on the surface and atmospheric
conditions of Venus, Mars, and Mercury. (See table,
“The Mariner Series,” on page 259.)
Mariner 1
The first American attempt to send a probe to Venus.
Guidance instructions from the ground stopped
reaching the rocket due to a problem with its antenna,
so the onboard computer took control. However, a
bug in the guidance software caused the rocket to veer
off course, and it was destroyed by the range safety
officer.
Mariner 2
Backup for Mariner 1, and the first probe to fly successfully
by another planet. The data it sent back confirmed
that Venus has a slow retrograde (backward)
spin, a very high surface temperature, and a thick
atmosphere made up mostly of carbon dioxide.
Mariner 2 passed Venus at a distance of 34,773 km on
December 14, 1962. The last transmission from the
probe was received on January 3, 1963; it remains in
solar orbit. 218
Mariner 3
A failed Mars probe. Its launch fairing failed to separate,
preventing a planned Mars flyby.
Mariner 4
A sister probe to Mariner 3 and the first spacecraft to
photograph Mars at close range; it came within 9,846
km of the Martian surface on July 14, 1965. The 21
pictures it sent back showed a cratered terrain and an
atmosphere much thinner than previously thought.
Based on its findings, scientists concluded that Mars
was probably a dead world, both geologically and biologically.
Later missions, however, showed that the
ancient region imaged by Mariner 4 was not typical
of the planet as a whole. In 1967, Mariner 4 returned
Mariner
to the vicinity of Earth, and engineers were able to use
the aging craft for a series of operational and telemetry
tests to improve their knowledge of techniques
needed for future interplanetary missions.
Mariner 5
A Venus flyby probe that came within 3,990 km of the
planet’s surface. Originally a backup for Mariner 4,
Mariner 5 was refurbished and sent to Venus instead.
Its main task was to find out more about Venus’s
atmosphere by using radio waves and measuring the
brightness of the atmosphere in ultraviolet light. It
also collected data on radiation and magnetic fields in
interplanetary space.
Mariner 6
A Mars probe that returned 75 images of the Martian
surface and flew by at a distance of 3,431 km. Disaster
almost struck while it was still on the ground. Ten days
before the scheduled launch, a faulty switch opened
the main valves on the Atlas booster, releasing the
pressure that supported the Atlas structure and causing
the rocket to crumple. Two ground crewman who,
Mariner 4 One of the first close-up (yet grainy) pictures
of Mars, sent back by Mariner 4. NASA/JPL
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