58 Mariner (venus, mars, & mercury flybys and orbiters) (US planetary missions)
Description
This article is from the Space FAQ, by Jon Leech leech@cs.unc.edu and Mark Bradford tla@surly.org with numerous contributions by others.
58 Mariner (venus, mars, & mercury flybys and orbiters) (US planetary missions)
MARINER 1, the first U.S. attempt to send a spacecraft to Venus, failed
minutes after launch in 1962. The guidance instructions from the ground
stopped reaching the rocket due to a problem with its antenna, so the
onboard computer took control. However, there turned out to be a bug in
the guidance software, and the rocket promptly went off course, so the
Range Safety Officer destroyed it. Although the bug is sometimes claimed
to have been an incorrect FORTRAN DO statement, it was actually a
transcription error in which the bar (indicating smoothing) was omitted
from the expression "R-dot-bar sub n" (nth smoothed value of derivative
of radius). This error led the software to treat normal minor variations
of velocity as if they were serious, leading to incorrect compensation.
MARINER 2 became the first successful probe to flyby Venus in December
of 1962, and it returned information which confirmed that Venus is a
very hot (800 degrees Fahrenheit, now revised to 900 degrees F.) world
with a cloud-covered atmosphere composed primarily of carbon dioxide
(sulfuric acid was later confirmed in 1978).
MARINER 3, launched on November 5, 1964, was lost when its protective
shroud failed to eject as the craft was placed into interplanetary
space. Unable to collect the Sun's energy for power from its solar
panels, the probe soon died when its batteries ran out and is now in
solar orbit. It was intended for a Mars flyby with MARINER 4.
MARINER 4, the sister probe to MARINER 3, did reach Mars in 1965 and
took the first close-up images of the Martian surface (22 in all) as it
flew by the planet. The probe found a cratered world with an atmosphere
much thinner than previously thought. Many scientists concluded from
this preliminary scan that Mars was a "dead" world in both the
geological and biological sense.
MARINER 5 was sent to Venus in 1967. It reconfirmed the data on that
planet collected five years earlier by MARINER 2, plus the information
that Venus' atmospheric pressure at its surface is at least 90 times
that of Earth's, or the equivalent of being 3,300 feet under the surface
of an ocean.
MARINER 6 and 7 were sent to Mars in 1969 and expanded upon the work
done by MARINER 4 four years earlier. However, they failed to take away
the concept of Mars as a "dead" planet, first made from the basic
measurements of MARINER 4.
MARINER 8 ended up in the Atlantic Ocean in 1971 when the rocket
launcher autopilot failed.
MARINER 9, the sister probe to MARINER 8, became the first craft to
orbit Mars in 1971. It returned information on the Red Planet that no
other probe had done before, revealing huge volcanoes on the Martian
surface, as well as giant canyon systems, and evidence that water once
flowed across the planet. The probe also took the first detailed closeup
images of Mars' two small moons, Phobos and Deimos.
MARINER 10 used Venus as a gravity assist to Mercury in 1974. The probe
did return the first close-up images of the Venusian atmosphere in
ultraviolet, revealing previously unseen details in the cloud cover,
plus the fact that the entire cloud system circles the planet in four
Earth days. MARINER 10 eventually made three flybys of Mercury from 1974
to 1975 before running out of attitude control gas. The probe revealed
Mercury as a heavily cratered world with a mass much greater than
thought. This would seem to indicate that Mercury has an iron core which
makes up 75 percent of the entire planet.
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