''Viking 1'' was the first of two

spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, ...

, along with '' Viking 2'', each consisting of an orbiter and a lander, sent to

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...

as part of

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...

's Viking program. The lander touched down on Mars on July 20, 1976, the first successful Mars lander in history. ''Viking 1'' operated on Mars for days (over 6 years) or Martian solar days, the longest Mars surface mission until the record was broken by the ''Opportunity'' rover on May 19, 2010.

Mission

Following launch using a

Titan Titan most often refers to: * Titan (moon), the largest moon of Saturn * Titans, a race of deities in Greek mythology Titan or Titans may also refer to: Arts and entertainment Fictional entities Fictional locations * Titan in fiction, fictiona ...

/ Centaur launch vehicle on August 20, 1975, and an 11-month cruise to Mars, the orbiter began returning global images of Mars about five days before orbit insertion. The ''Viking 1'' Orbiter was inserted into Mars orbit on June 19, 1976, and trimmed to a 1,513 x 33,000 km, 24.66 h site certification orbit on June 21. Landing on Mars was planned for July 4, 1976, the United States Bicentennial, but imaging of the primary landing site showed it was too rough for a safe landing. The landing was delayed until a safer site was found, and took place instead on July 20, the seventh anniversary of the

Apollo 11 Apollo 11 (July 16–24, 1969) was the American spaceflight that first landed humans on the Moon. Commander Neil Armstrong and lunar module pilot Buzz Aldrin landed the Apollo Lunar Module ''Eagle'' on July 20, 1969, at 20:17 UTC, ...

Moon landing. The lander separated from the orbiter at 08:51 UTC and landed at Chryse Planitia at 11:53:06 UTC. It was the first attempt by the United States at landing on Mars.

Orbiter

The instruments of the orbiter consisted of two

vidicon Video camera tubes were devices based on the cathode ray tube that were used in television cameras to capture television images, prior to the introduction of charge-coupled device (CCD) image sensors in the 1980s. Several different types of tubes ...

cameras for imaging (VIS), an infrared spectrometer for water vapor mapping (MAWD) and infrared radiometers for thermal mapping (IRTM). The orbiter primary mission ended at the beginning of

solar conjunction Solar conjunction generally occurs when a planet or other Solar System object is on the opposite side of the Sun from the Earth. From an Earth reference, the Sun will pass between the Earth and the object. Communication with any spacecraft in sol ...

on November 5, 1976. The extended mission commenced on December 14, 1976, after solar conjunction. Operations included close approaches to Phobos in February 1977. The periapsis was reduced to 300 km on March 11, 1977. Minor orbit adjustments were done occasionally over the course of the mission, primarily to change the walk rate — the rate at which the areocentric longitude changed with each orbit, and the periapsis was raised to 357 km on July 20, 1979. On August 7, 1980, ''Viking 1'' Orbiter was running low on attitude control gas and its orbit was raised from 357 × 33943 km to 320 × 56,000 km to prevent impact with Mars and possible contamination until the year 2019. Operations were terminated on August 17, 1980, after 1,485 orbits. A 2009 analysis concluded that, while the possibility that ''Viking 1'' had impacted Mars could not be ruled out, it was most likely still in orbit. More than 57,000 images were sent back to Earth.

Lander

The lander and its aeroshell separated from the orbiter on July 20 at 08:51 UTC. At the time of separation, the lander was orbiting at about . The aeroshell's retrorockets fired to begin the lander de-orbit maneuver. After a few hours at about altitude, the lander was reoriented for atmospheric entry. The aeroshell with its ablative heat shield slowed the craft as it plunged through the atmosphere. During this time, entry science experiments were performed by using a retarding potential analyzer, a mass spectrometer, as well as pressure, temperature, and density sensors. At altitude, traveling at about , the 16 m diameter lander parachutes deployed. Seven seconds later the aeroshell was jettisoned, and 8 seconds after that the three lander legs were extended. In 45 seconds the parachute had slowed the lander to . At altitude, retrorockets on the lander itself were ignited and, 40 seconds later at about , the lander arrived on Mars with a relatively light jolt. The legs had honeycomb aluminum shock absorbers to soften the landing. The landing rockets used an 18-nozzle design to spread the hydrogen and nitrogen exhaust over a large area. NASA calculated that this approach would mean that the surface would not be heated by more than one 1 °C (1.8 °F), and that it would move no more than of surface material. Since most of Viking's experiments focused on the surface material a more straightforward design would not have served. The ''Viking 1'' lander touched down in western Chryse Planitia ("Golden Plain") at at a reference altitude of relative to a reference ellipsoid with an equatorial radius of and a flatness of 0.0105 (22.480° N, 47.967° W planetographic) at 11:53:06 UTC (16:13 local Mars time). Approximately of propellants were left at landing. Transmission of the first surface image began 25 seconds after landing and took about four minutes (see below). During these minutes the lander activated itself. It erected a high-gain antenna pointed toward Earth for direct communication and deployed a meteorology boom mounted with sensors. In the next seven minutes the second picture of the 300° panoramic scene (displayed below) was taken. On the day after the landing the first colour picture of the surface of Mars (displayed below) was taken. The seismometer failed to uncage, and a sampler arm locking pin was stuck and took five days to shake out. Otherwise, all experiments functioned normally. The lander had two means of returning data to Earth: a relay link up to the orbiter and back, and by using a direct link to Earth. The orbiter could transmit to Earth (S-band) at 2,000 to 16,000 bit/s (depending on distance between Mars and Earth), and the lander could transmit to the orbiter at 16,000 bit/s. The data capacity of the relay link was about 10 times higher than the direct link. The lander had two facsimile cameras; three analyses for metabolism, growth or photosynthesis; a gas chromatograph-mass spectrometer (GCMS); an x-ray fluorescence spectrometer; pressure, temperature and wind velocity sensors; a three-axis seismometer; a magnet on a sampler observed by the cameras; and various engineering sensors. The ''Viking 1'' lander was named the Thomas Mutch Memorial Station in January 1981 in honour of Thomas A. Mutch, the leader of the Viking imaging team. The lander operated for 2245

sol Sol or SOL may refer to: Astronomy * The Sun Currency * SOL Project, a currency project in France * French sol, or sou * Argentine sol * Bolivian sol, the currency of Bolivia from 1827 to 1864 * Peruvian sol, introduced in 1991 * Peruvian sol ...

s (about 2306 Earth days or 6 years) until November 11, 1982, (sol ), when a faulty command sent by ground control resulted in loss of contact. The command was intended to uplink new battery charging software to improve the lander's deteriorating battery capacity, but it inadvertently overwrote data used by the antenna pointing software. Attempts to contact the lander during the next four months, based on the presumed antenna position, were unsuccessful. In 2006 the ''Viking 1'' lander was imaged on the Martian surface by the '' Mars Reconnaissance Orbiter''.

Mission results

Search for life

''Viking 1'' carried a biology experiment whose purpose was to look for evidence of life. The ''Viking'' lander biological experiments weighed 15.5 kg (34 lbs) and consisted of three subsystems: the pyrolytic release experiment (PR), the labeled release experiment (LR), and the gas exchange experiment (GEX). In addition, independent of the biology experiments, Viking carried a gas chromatograph-mass spectrometer (GCMS) that could measure the composition and abundance of organic compounds in the Martian soil. The results were surprising and interesting: the GCMS gave a negative result; the PR gave a negative result, the GEX gave a negative result, and the LR gave a positive result. Viking scientist Patricia Straat stated in 2009, "Our (LR) experiment was a definite positive response for life, but a lot of people have claimed that it was a false positive for a variety of reasons." Most scientists now believe that the data were due to inorganic chemical reactions of the soil; however, this view may be changing after the recent discovery of near-surface ice near the ''Viking'' landing zone. Some scientists still believe the results were due to living reactions. No organic chemicals were found in the soil. However, dry areas of

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...

do not have detectable organic compounds either, but they have organisms living in the rocks. Mars has almost no ozone layer, unlike the Earth, so UV light sterilizes the surface and produces highly reactive chemicals such as peroxides that would oxidize any organic chemicals. The ''Phoenix'' Lander discovered the chemical

perchlorate A perchlorate is a chemical compound containing the perchlorate ion, . The majority of perchlorates are commercially produced salts. They are mainly used as oxidizers for pyrotechnic devices and to control static electricity in food packaging. ...

in the Martian soil. Perchlorate is a strong oxidant so it may have destroyed any organic matter on the surface. If it is widespread on Mars, carbon-based life would be difficult at the soil surface.

First panorama by ''Viking 1'' lander

''Viking 1'' image gallery

File:Titan 3E-Centaur launches with Viking 1.jpg, Launch of the ''Viking 1'' probe (20 August 1975). File:Viking lander model.jpg, Model of ''Viking'' Lander File:Mars Viking 12a001.png, First image by the ''Viking 1'' lander from the surface of Mars, showing lander's footpad. File:Mars Viking 12a240.png, ''Viking 1'' lander image of a Martian sunset over Chryse Planitia. File:Mars Viking 11d128.png, Trenches dug by soil sampler device. File:PIA00563-Viking1-FirstColorImage-19760721.jpg, First colour image taken by the ''Viking 1'' lander (21 July 1976). File:Mars Viking 11h016.png, ''Viking 1'' lander site (11 February 1978). File:PSP 001521 2025 RED VL-1 lander.png, ''Viking 1'' lander taken by Mars Reconnaissance Orbiter (December 2006). File:Mars Viking 11a097.png, Dunes and large boulder. Pole in the centre is an instrument boom. File:12e189(Sol379-7.84).jpg, ''Viking 1'' Lander Camera 2 Sky at sunrise (Low Resolution Colour) Sol 379 07:50

Test of general relativity

Gravitational time dilation is a phenomenon predicted by the theory of

general relativity General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics ...

whereby time passes more slowly in regions of lower gravitational potential. Scientists used the lander to test this hypothesis, by sending radio signals to the lander on Mars, and instructing the lander to send back signals, in cases which sometimes included the signal passing close to the Sun. Scientists found that the observed

Shapiro delay The Shapiro time delay effect, or gravitational time delay effect, is one of the four classic solar-system tests of general relativity. Radar signals passing near a massive object take slightly longer to travel to a target and longer to return t ...

s of the signals matched the predictions of general relativity.

Orbiter shots

File:Olympus Mons alt.jpg , Olympus Mons File:PIA17940-MartianMorningClouds-VikingOrbiter1-1976-20140212.jpg, Morning Clouds on

(taken in 1976) File:Streamlined Islands in Maja Valles.jpg, Streamlined islands in

Lunae Palus quadrangle The Lunae Palus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is also referred to as MC-10 (Mars Chart-10). Lunae Planum and parts o ...

. File:Viking Teardrop Islands.jpg, Tear-drop shaped islands at Oxia Palus quadrangle. File:Chryse Planitia Scour Patterns.jpg, Scour patterns located in

. File:Detail of Maja Valles Flow.jpg,

was eroded by large amounts of liquid water. File:Phobos-viking1.jpg, Phobos, a mosaic of images taken in 1978. File:Cobres crater Viking 1 mosaic.png, Mosaic of 8 images showing Cobres crater

Lander location

Notes

References

External links

''Viking 1'' Mission Profile
b
NASA's Solar System Exploration

45 years ago: ''Viking'' 1 Touches Down on Mars
{{Authority control Missions to Mars Viking program 1975 in spaceflight August 1975 events in the United States Derelict landers (spacecraft) Lunae Palus quadrangle Nuclear-powered robots Spacecraft launched by Titan rockets Soft landings on Mars Spacecraft launched in 1975 1975 in Florida 1976 on Mars