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| trans_band = | trans_frequency = | trans_bandwidth = | trans_capacity = | trans_coverage = | trans_TWTA = | trans_EIRP = | trans_HPBW = Flagship Program>Flagship| previous_mission = None| next_mission = Viking 2| insignia = | insignia_caption = | insignia_alt = | insignia_size = }}Viking 1 was the first of two spacecraft, along with Viking 2, each consisting of an orbiter and a lander, sent to Mars as part of NASA'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 {{age in days|1976|07|20|1982|11|13|format=commas}} days (over 6{{frac|1|4}} years) or {{age in sols|1976|07|20|1982|11|13|format=commas}} Martian solar days, the longest Mars surface mission until the record was broken by the Opportunity rover on May 19, 2010.WEB,weblink Mars Exploration Rover, mars.nasa.gov, mars.nasa.gov,

Mission

Following launch using a Titan/Centaur launch vehicle on August 20, 1975, and an 11-month cruise to Mars,WEB,weblink 20 August 1975, Launch of Viking 1, Loff, Sarah, August 20, 2015, NASA, July 18, 2019, 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,BOOK,weblink Encyclopedia of Space and Astronomy, Angelo, Joseph A., May 14, 2014, Infobase Publishing, 9781438110189, 641, en, 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.BOOK,weblink Magnificent Mars, Croswell, Ken, October 21, 2003, Simon and Schuster, 9780743226011, 23, en, The landing was delayed until a safer site was found, and took place instead on July 20, the seventh anniversary of the Apollo 11 Moon landing.BOOK,weblink The International Atlas of Mars Exploration: Volume 1, 1953 to 2003: The First Five Decades, Stooke, Philip J., September 24, 2012, Cambridge University Press, 9781139560252, en, The lander separated from the orbiter at 08:51 UTC and landed at Chryse Planitia at 11:53:06 UTC.{{NSSDC|id=1975-075A|access-date=July 18, 2019|title=Viking 1 Orbiter}} It was the first attempt by the United States at landing on Mars.WEB,weblink Chronology of Mars Exploration, history.nasa.gov, August 16, 2019,

Orbiter

The instruments of the orbiter consisted of two vidicon cameras for imaging, an infrared spectrometer for water vapor mapping, and infrared radiometers for thermal mapping.JOURNAL, Soffen, G.A., Snyder, C.W., August 1976, The First Viking Mission to Mars, Science, New Series, 193, 4255, 759–766, 1976Sci...193..759S, 10.1126/science.193.4255.759, 1742875, 17747776,

Lander

(File:Viking Aeroshell - GPN-2000-001903.jpg|left|thumb|Viking aeroshell)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 {{convert|5|km/s|abbr=off|sp=us}}. The aeroshell's retrorockets fired to begin the lander de-orbit maneuver. After a few hours at about {{convert|300|km|abbr=off|sp=us}} 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 {{convert|6|km|abbr=on}} altitude, traveling at about {{convert|250|m/s|abbr=off|sp=us}}, 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 {{convert|60|m/s|abbr=off|sp=us}}. At {{convert|1.5|km|abbr=on}} altitude, retrorockets on the lander itself were ignited and, 40 seconds later at about {{convert|2.4|m/s|abbr=on}}, the lander arrived on Mars with a relatively light jolt. The legs had honeycomb aluminum shock absorbers to soften the landing.(File:Documentary clip of Viking 1 landing (JPL-19760720-VIKINGf-0002-AVC2002151).webm|thumb|Documentary clip recounting the Viking 1 landing with animation and video footage of the control centre)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 Â°C (1.8 Â°F), and that it would move no more than {{convert|1|mm|sigfig=1|abbr=off|sp=us}} of surface material. Since most of Viking's experiments focused on the surface material a more straightforward design would not have served.WEB, Viking 1 Lander Mission Profile,weblink University of Texas, November 10, 2022, The Viking 1 lander touched down in western Chryse Planitia ("Golden Plain") at {{Coord|22.697|N|312.05|E|globe:Mars}} at a reference altitude of {{convert|−2.69|km|sp=us}} relative to a reference ellipsoid with an equatorial radius of {{convert|3,397|km|sp=us}} and a flatness of 0.0105 (22.480° N, 47.967° W planetographic) at 11:53:06 UTC (16:13 local Mars time). Approximately {{convert|22|kg}} 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.JOURNAL, Mutch, T.A., etal, August 1976, The Surface of Mars: The View from the Viking 1 Lander, Science, New Series, 193, 4255, 791–801, 1976Sci...193..791M, 10.1126/science.193.4255.791, 1742881, 17747782, 42661323, 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.WEB,weblink Viking Mission to Mars JPL, The data capacity of the relay link was about 10 times higher than the direct link.{{Wide image|Mars Viking 12a001.png|800px|First "clear" image ever transmitted from the surface of Mars – shows rocks near the Viking 1 Lander (20 July 1976). The haze on the left is possibly dust that had recently been kicked up by the landing rockets. Because of the "slow scan" facsimile nature of the cameras, the dust settled by mid-image.}}The lander had two facsimile cameras; three analyses for metabolism, growth or photosynthesis; a gas chromatograph-mass spectrometer; 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.(File:PSP 001521 2025 RED VL-1 lander.png|thumb|Photo of the Viking 1 Mars lander taken by the Mars Reconnaissance Orbiter in 2006)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.WEB, NASA – NSSDCA – Spacecraft – Details,weblink nssdc.gsfc.nasa.gov, March 5, 2021, The lander operated for 2,245 sols (about 2,306 Earth days or 6 years) until November 11, 1982 (sol {{age in sols|1975|07|20|1982|11|11|format=commas}}), 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.REPORT, D. J. Mudgway, NASA Jet Propulsion Laboratory, 1983, Telecommunications and Data Acquisition Systems Support for the Viking 1975 Mission to Mars,weblink June 22, 2009, In 2006, the Viking 1 lander was imaged on the Martian surface by the Mars Reconnaissance Orbiter.REPORT, NASA, 2006, NASA Mars Orbiter Photographs Spirit and Vikings on the Ground,weblink July 20, 2011,

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 that could measure the composition and abundance of organic compounds in the Martian soil.WEB,weblinkweblink" title="web.archive.org/web/20141020034248weblink">weblink dead, Life on Mars, October 20, 2014, www.msss.com, The results were surprising and interesting: the spectrometer gave a negative result; the PR gave a negative result, the GEX gave a negative result, and the LR gave a positive result.Viking Data May Hide New Evidence For Life. Barry E. DiGregorio, July 16, 2000. 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."Viking 2 Likely Came Close to Finding H2O. {{webarchive |url=https://web.archive.org/web/20090930025048weblink |date=September 30, 2009 }} Irene Klotz, Discovery News, September 28, 2009. 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.JOURNAL, Stuurman, C.M., Osinski, G.R., Holt, J.W., Levy, J.S., Brothers, T.C., Kerrigan, M., Campbell, B.A., SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars, Geophysical Research Letters, September 28, 2016, 43, 18, 9484–9491, 10.1002/2016gl070138, 2016GeoRL..43.9484S, free, Some scientists still believe the results were due to living reactions. No organic chemicals were found in the soil. However, dry areas of Antarctica do not have detectable organic compounds either, but they have organisms living in the rocks.Friedmann, E. 1982. Endolithic Microorganisms in the Antarctic Cold Desert. Science: 215. 1045–1052. 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.Hartmann, W. 2003. A Traveler's Guide to Mars. Workman Publishing. NY NY. The Phoenix Lander discovered the chemical perchlorate in the Martian soil. Perchlorate is a strong oxidant so it may have destroyed any organic matter on the surface.Alien Rumors Quelled as NASA Announces Phoenix Perchlorate Discovery. {{webarchive |url=https://web.archive.org/web/20100904132551weblink |date=September 4, 2010 }} A.J.S. Rayl, August 6, 2008. If it is widespread on Mars, carbon-based life would be difficult at the soil surface.

First panorama by Viking 1 lander

{{Wide image|Mars_Viking_12a002.png|1500px|First panoramic view by Viking 1 from the surface of Mars. Captured on 20 July 1976.}}

Viking 1 image gallery

File:Titan 3E-Centaur launches with Viking 1.jpg|Launch of the Viking 1 probe (20 August 1975)File:NASM-A19790215000-NASM2016-02690.jpg|Proof test article of the Viking Mars LanderFile:Mars Viking 12a001.png|First image by the Viking 1 lander from the surface of Mars, showing lander's footpadFile:Mars Viking 12a240.png|Viking 1 lander image of a Martian sunset over Chryse PlanitiaFile:Mars Viking 11d128.png|Trenches dug by soil sampler deviceFile: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: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

File:Cassini-science-br.jpg|thumb|right|150px|High-precision test of general relativity by the Cassini space probe (artist's impression)]]Gravitational time dilation is a phenomenon predicted by the theory of general relativity 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 delays of the signals matched the predictions of general relativity.JOURNAL, 6, Reasenberg, R. D., Shapiro, I. I., MacNeil, P. E., Goldstein, R. B., Breidenthal, J. C., Brenkle, J. P., Cain, D. L., Kaufman, T. M., Komarek, T. A., Zygielbaum, A. I., December 1979, Viking relativity experiment – Verification of signal retardation by solar gravity, Astrophysical Journal Letters, 234, L219–L221, 1979ApJ...234L.219R, 10.1086/183144, free,

Orbiter shots

File:Olympus Mons alt.jpg | Olympus MonsFile:PIA17940-MartianMorningClouds-VikingOrbiter1-1976-20140212.jpg|Morning Clouds on Mars (taken in 1976)File:Streamlined Islands in Maja Valles.jpg|Streamlined islands in Lunae Palus quadrangleFile:Viking Teardrop Islands.jpg|Tear-drop shaped islands at Oxia Palus quadrangleFile:Chryse Planitia Scour Patterns.jpg|Scour patterns located in Lunae Palus quadrangleFile:Detail of Maja Valles Flow.jpg|Lunae Palus quadrangle was eroded by large amounts of liquid water.File:Phobos-viking1.jpg|Phobos, a mosaic of images taken in 1978File:Cobres crater Viking 1 mosaic.png|Mosaic of eight images showing Cobres crater

Lander location

{{Features and artificial objects on Mars}}

See also

• Exploration of Mars
• List of missions to Mars
• List of Mars orbiters
• Timeline of artificial satellites and space probes

Notes

{{notelist}}

References

{{Reflist|30em}}

External links

{{commons category|Viking 1}}

• weblink" title="web.archive.org/web/20061002000557weblink">Viking 1 Mission Profile by NASA's Solar System Exploration
• Image – Viking 1 Approaches Mars
• 45 years ago: Viking 1 Touches Down on Mars

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