882 Encyclopedia of the Solar System
In what follows, we concentrate upon successes, but
those must be seen as just the most visible parts of a re-
markable, decades-long striving toward a possible breakout
of humanity beyond the bounds of Earth.
In addition to the Web page listed for each mission below,
a site with a brief story of every publicly acknowledged
Mars mission is given at http://www.planetary.org/learn/missions/
marsmissions.html.
Mariner 4
Mars launch opportunities occur about every 26 months.
In both the USA and the USSR, the October 1960 win-
dow was the favored first chance. The Soviets did launch,
with two upper stage vehicle failures. During the 1962 win-
dow, the Soviets tried three launches, one of which sent
Mars 1toward the planet. That spacecraft failed en route.
In 1964, NASA launched twoAtlas-Agenaswith one suc-
cess.Mariner 4flew by Mars and returned 22 images of
the cratered southern highlands, leading to the impression
of a Moon-like Mars, proved false by later missions. (See
http://www.jpl.nasa.gov/missions/past/mariner3-4.html.))
Mariner 6 and 7
Two Mars flyby missions,Mariner 6 and 7, launched by
Atlas-Centaursin 1969, demonstrated the rapid advance
of deep-space data acquisition technology. Their imaging
was greatly improved over that ofMariner 4in both qual-
ity and quantity, and in addition infrared spectrometry
gave some first indications of Martian surface compositions.
They still covered mainly southern, including polar, ancient
landforms, omitting the vast volcanoes and canyons dis-
covered byMariner 9. (See http://www.jpl.nasa.gov/missions/past/
mariner6-7.)
Mars 2 and 3
During the 1971 Mars window, the USSR and USA each
launched two missions. The SovietMars 2and 3 orbiter/
landers both arrived successfully into orbit at the planet;
Mars 2returned some orbital science data but its lander
crashed.Mars 3, in addition to its orbital operations, deliv-
ered its lander with a small tethered mobile platform. But
the transmissions from the lander ceased only 20 seconds af-
ter touchdown. (See http://www.earthandspace.org/mars23.htm.))
Mariner 9
TheAtlas-CentaurcarryingMariner 8failed butMariner
9 became the most rewarding Mars mission up to its time,
waiting out a global dust storm in orbit and then sending im-
agery of most of the Martian surface until its mission ended
in 1972, revealing enormous volcanoes, canyons, appar-
ent river channel networks, sapping collapse features and
clouds, plus imagery of the two small moons, Phobos and
Deimos. (See http://www.jpl.nasa.gov/missions/past/mariner8-9.)Mars 4, 5, 6, and 7
At the 1973 opportunity, the Soviets made an all out ef-
fort to upstage the AmericanVikingmissions planned for- They launched four large spacecraft, all of which ar-
rived in the vicinity of Mars but each of which ultimately
failed for a different reason.Mars 4failed to brake into orbit
but did return some flyby data;Mars 5entered orbit, sent
some images and failed after 22 days;Mars 6released a lan-
der that failed during descent;Mars 7’s lander missed the
planet. (See athena.cornell.edu/marsfacts/pastmissions
70s.html.)
Viking 1 and 2
In 1975 two large NASA orbiter/landers,Viking 1and 2 ,
were launched by powerfulTitan-Centaurs. Arriving in
June and July 1976, they entered orbit and began sur-
veying for landing sites. TheViking 1lander set down in
Chryse Planitia on 20 July and theViking 2lander de-
scended to Utopia Planitia on 3 September on the opposite
side of Mars. While the orbiters began imaging the whole
planet and making spectrometric remote sensing observa-
tions, during descent the landers measured atmospheric
composition. Then the landers began to operate a suite of in-
struments for imaging their surroundings and determining
meteorological, geological and biological properties. At
first, microbial activity was suspected, but eventually most
scientists concluded that no life did or could exist in the
soil samples. (See http://www.jpl.nasa.gov/missions/pastmissions.
cfm.)Phobos 1 and 2
After a long pause in Martian exploration, in 1988 two
large and complex Soviet spacecraft,Phobos 1and 2 , were
launched byProtonvehicles toward the vicinity of Mars.
Phobos 1was lost en route due to a human error in ground
control.Phobos 2arrived and began phasing orbits for a
rendezvous with the little moon, where it was to make
close-up observations and deposit two small landing pack-
ages, one of them a hopping rover. Imagery and some other
data of Phobos and Mars were obtained, but the spacecraft
failed before the landings could occur. (See http://www.iki.rssi.ru/
IPL/phobos.html.)Mars Pathfinder and Mars Global Surveyor
The 1996 launch window saw the revival of detailed Amer-
ican exploration of Mars. NASA’sPathfinderdelivered a
lander and a small rover, named Sojourner, which explored
nearby surroundings in the Ares Vallis outwash plain. The
Global Surveyorspacecraft entered an eccentric orbit and