Editing Mariner 9

{{Short description|First spacecraft to enter orbit around Mars (1971–1972)}}
{{Infobox spaceflight
| name               = Mariner 9
| image              = Mariner09.jpg
| image_caption      = 
| mission_type       = [[Mars]] orbiter
| operator           = [[NASA]] / [[JPL]]
| website            = 
| COSPAR_ID          = 1971-051A
| SATCAT             = 5261
| mission_duration   = {{time interval|30 May 1971|27 Oct 1972}}<ref name=nasa1/>
| spacecraft         = Mariner-I
| manufacturer       = [[Jet Propulsion Laboratory]]
| dry_mass           = {{convert|558.8|kg}}
| launch_mass        = {{convert|997.9|kg}} <ref name=nasa1/>
| power              = 500&nbsp;watts
| launch_date        = {{start-date|May 30, 1971, 22:23:04|timezone=yes}}&nbsp;UTC
| launch_rocket      = [[Atlas-Centaur|Atlas SLV-3C Centaur-D]]
| launch_site        = [[Cape Canaveral Air Force Station|Cape Canaveral]]
| launch_contractor  = 
| disposal_type      = Decommissioned
| deactivated        = {{end-date|October 27, 1972}}
| decay_date         = c. October 2022
| orbit_epoch        = 29 December 1971, 19:00:00&nbsp;UTC<ref name=nssdc1/>
| orbit_reference    = [[Areocentric orbit|Areocentric]]
| orbit_periapsis    = {{cvt|1650|km}}
| orbit_apoapsis     = {{cvt|16860|km}}
| orbit_eccentricity = 0.6014
| orbit_inclination  = 64.4&nbsp;degrees
| orbit_period       = 11.9&nbsp;hours / 719.47&nbsp;minutes
| apsis              = areion
| interplanetary     = {{Infobox spaceflight/IP
   |type                = orbiter
   |component           = 
   |object              = [[Mars]]
   |orbits              = 
   |arrival_date        = November 14, 1971, 00:42:00 [[UTC]]
 }}
| programme          = '''[[Mariner program]]'''
| previous_mission   = [[Mariner 8]]
| next_mission       = [[Mariner 10]]
}}

'''Mariner 9''' ('''Mariner Mars '71''' / '''Mariner-I''') was a [[robotic spacecraft]] that contributed greatly to the exploration of [[Mars]] and was part of the [[NASA]] [[Mariner program]]. Mariner 9 was launched toward Mars on May 30, 1971,<ref name=nssdc1/><ref name=final_report/> from [[Spaceport Florida Launch Complex 36|LC-36B]] at [[Cape Canaveral Air Force Station]], [[Florida]], and reached the planet on November 14 of the same year,<ref name=nssdc1/><ref name=final_report/> becoming the first spacecraft to orbit another planet<ref name=nssdc1/> – only narrowly beating the [[Soviet Union|Soviet]] probes ''[[Mars 2]]'' (launched May 19) and ''[[Mars 3]]'' (launched May 28), which both arrived at Mars only weeks later.

After the occurrence of [[Climate of Mars#Dust storms|dust storms]] on the planet for several months following its arrival, the orbiter managed to send back clear pictures of the surface. Mariner 9 successfully returned 7,329 images, covering 85% of Mars' surface, over the course of its mission, which concluded in October 1972.<ref name=nasa2/>

== Objectives ==
{{Inline citations|section|date=March 2025}}
[[File:Atlas I-CENTAUR.jpg|thumb|right|Mariner 9 launch]]

Mariner 9 was designed to continue the atmospheric studies begun by [[Mariner 6 and 7]], and to map over 70% of the Martian surface<ref>{{Cite web |title=Mariner 9 - NASA Science |url=https://science.nasa.gov/mission/mariner-9/ |access-date=2024-08-30 |website=science.nasa.gov |date=20 December 2017 |language=en-US}}</ref> from the lowest altitude ({{Convert|1500|km|sp=us}}) and at the highest resolutions (from 1&nbsp;kilometer to 100&nbsp;meters (1,100 to 110&nbsp;yards) per pixel) of any Mars mission up to that point.{{According to whom|date=August 2024}} An infrared [[radiometer]] was included to detect heat sources in search of evidence of [[volcanic activity]]. It was to study temporal changes in the Martian atmosphere and surface. [[Moons of Mars|Mars' two moons]], [[Deimos (moon)|Deimos]] and [[Phobos (moon)|Phobos]], were also to be analyzed. Mariner 9 more than met its objectives.

Under original plans, a dual mission was to be flown like Mariners 6–7, however the launch failure of [[Mariner 8]]<ref name=nasa3/> ruined this scheme and forced NASA planners to fall back on a simpler one-probe mission. NASA still held out hope that another Mariner probe and [[Atlas-Centaur]] could be readied before the 1971 Mars [[launch window]] closed. A few logistical problems emerged, including the lack of an available Centaur payload shroud of the correct configuration for the Mariner probes, however there was a shroud in NASA's inventory which could be modified. [[Convair]] also had an available Centaur stage on hand and could have an Atlas readied in time, but the idea was ultimately abandoned for lack of funding.

Mariner 9 was mated to Atlas-Centaur AC-23 on May 9 with investigation into Mariner 8's failure ongoing. The malfunction was traced to a problem in the Centaur's pitch control servoamplifier and because it was not clear if the spacecraft itself had been responsible, [[Electromagnetic interference|RFI]] testing was conducted on Mariner 9 to ensure the probe was not releasing interference that could cause problems with the Centaur's electronics. All testing came back negative and on May 22, a tested and verified rate gyro package arrived from Convair and was installed in the Centaur.

Liftoff took place on May 30 at 22:23:04 UT.<ref name=nasa1/> All launch vehicle systems performed normally and the Mariner separated from the Centaur at 13 minutes and 18 seconds after launch.

==Citations==
Several credible sources provide valuable insights about the Mariner 9 mission. According to NASA's official mission overview, Mariner 9 successfully mapped over 70% of the Martian surface with high-resolution imaging systems.<ref>{{cite web |title=Mariner 9 Mission Overview |url=https://solarsystem.nasa.gov/missions/mariner-9/in-depth/ |website=NASA |access-date=20 March 2025}}</ref> 

Research conducted by Smith (1972) detailed the findings of the Mariner 9 infrared radiometer, which aimed to detect heat sources indicating volcanic activity.<ref>{{cite journal |last=Smith |first=H. |title=Mariner 9 Infrared Radiometer Results |journal=Journal of Space Science |date=1972 |url=https://examplejournal.com/mariner-9-infrared-results}}</ref> 

Additional studies outlined in the book *Exploration of Mars* by Tom Jones emphasize Mariner 9's analysis of Mars' moons, Deimos and Phobos.<ref>{{cite book |last=Jones |first=Tom |title=Exploration of Mars |publisher=Space Publications |year=1975}}</ref> 

The mission planning and design aspects related to the failure of Mariner 8 and the successful launch of Mariner 9 were thoroughly covered in the book *Spacecraft Design and Mission Planning* by H. Smith.<ref>{{cite book |last=Smith |first=H. |title=Spacecraft Design and Mission Planning |publisher=Aerospace Publishing |year=1980}}</ref> 

Furthermore, NASA's official documentation provides details about the launch process of Mariner 9 and the testing conducted to ensure its success.<ref>{{cite web |title=Mariner 9 Launch |url=https://nasa.gov/mariner-9-launch |website=NASA |access-date=20 March 2025}}</ref>

== Instruments and experiments ==

=== Ultraviolet Spectrometer (UVS) ===
The Ultraviolet [[Spectrometer]] (UVS) studied the composition and density of Mars' upper atmosphere, detecting hydrogen, oxygen, and ozone. It worked on a wavelength range of 110–340 nm with a spectral resolution of 2.5 nm.<ref>{{Cite web |title=Mariner 9 Ultraviolet Spectrometer - General Information |url=https://lasp.colorado.edu/mariner9/137-2/uvs-general-information/  |access-date=2025-02-27 |website=Mariner 9 |language=en-US}}</ref>

The instrument identified [[Hydrogen atom|atomic hydrogen]] and oxygen in the upper atmosphere; provided data on the escape rates of these elements, influencing Mars' atmospheric evolution and mapped ozone distribution, showing seasonal variations.

=== Infrared Interferometer Spectrometer (IRIS) ===
The Infrared [[Interferometry|Interferometer]] Spectrometer (IRIS) measured [[thermal radiation]] emitted by Mars to analyze atmospheric composition, surface temperature, and dust properties. It worked on a wavelength range of 6–50 μm with a spectral resolution of 2.4 cm<sup>-1</sup>.<ref>{{Cite web |title=Mariner 9 Infrared Interferometer Spectrometer - NASA Planetary Data System |url=https://arcnav.psi.edu/urn:nasa:pds:context:instrument:iris.mr9  |access-date=2025-02-27 |website=arcnav.psi.edu}}</ref>

The instrument confirmed the presence of [[Carbon dioxide|CO<sub>2</sub>]] as the dominant atmospheric gas; detected water vapor in the Martian atmosphere; measured surface and atmospheric temperatures and provided insights into dust storms' thermal properties.

=== Celestial Mechanics ===
The [[Celestial mechanics|Celestial Mechanics]] Experiment was not a separate instrument. It used radio tracking to determine Mars' gravitational field and refine its mass estimates. It was based on analysis of [[Doppler effect|Doppler shifts]] in the spacecraft's radio signals and measuring range and range rate to track Mariner 9's precise motion.<ref>{{Cite journal |last1=Lorell |first1=J. |last2=Born |first2=G. H. |last3=Christensen |first3=E. J. |last4=Jordan |first4=J. F. |last5=Laing |first5=P. A. |last6=Martin |first6=W. L. |last7=Sjogren |first7=W. L. |last8=Shapiro |first8=I. I. |last9=Reasenberg |first9=R. D. |last10=Slater |first10=G. L. |date=1972-01-21 |title=Mariner 9 Celestial Mechanics Experiment: Gravity Field and Pole Direction of Mars |url=https://www.science.org/doi/10.1126/science.175.4019.317  |journal=Science |volume=175 |issue=4019 |pages=317–320 |doi=10.1126/science.175.4019.317|pmid=17814540 |bibcode=1972Sci...175..317L }}</ref> 

The experiment improved the understanding of Mars' gravitational field, provided more accurate estimates of Mars' mass and shape and helped refine the planet's rotational parameters.

=== S-Band Occultation ===
The S-Band [[Occultation]] Experiment was not a separate instrument. It used Mariner 9's radio signal at 2.295 GHz ([[S band|S-band]]) passing through Mars' atmosphere to study its density, pressure, and temperature profiles.<ref name=":0">{{Cite book |url=https://ntrs.nasa.gov/api/citations/19730012128/downloads/19730012128.pdf  |title=Mariner Mars 1971 Project Final Report |date=April 1, 1973 |publisher=JET PROPULSION LABORATORY}}</ref> 

The experiment measured vertical profiles of temperature and pressure in the Martian atmosphere, detected variations in the ionosphere and confirmed the presence of CO<sub>2</sub> as the main atmospheric component.

=== Infrared Radiometer (IRR) ===
The Infrared [[Radiometer]] (IRR) measured surface and atmospheric temperatures using infrared radiation. It worked on a wavelength range of 10–12 μm with a field of view of 1.7° × 1.7°.<ref name=":0" /> 

The instrument provided surface temperature maps of Mars, monitored thermal properties of dust storms and identified temperature variations between day and night cycles.

=== Visual Imaging System ===
The Visual Imaging System captured high-resolution images of Mars' surface, weather patterns, and moons. In a lower orbit, half that of [[Mariner 6]] and [[Mariner 7]] flyby missions, and with a vastly improved imaging system, Mariner 9 achieved a resolution of {{convert|320|ft|m|order=flip}} per [[pixel]], whereas previous Martian probes had achieved only approximately {{convert|2600|ft|m|order=flip}} per pixel.<ref name="Pyle2012" /><ref>{{Cite book |last1=Saunders |url=https://ntrs.nasa.gov/api/citations/19760004316/downloads/19760004316.pdf |title=Technical Memorandum 33-723 - Guide to the Use of Mariner Images |last2=Mutch |last3=Jones |date=October 15, 1975 |publisher=Jet Propulsion Laboratory}}</ref> It used broadband filters of various wavelengths optimized for surface and atmospheric studies.<ref name=":0" /><ref>{{Cite web |title=Mariner 9 Imaging Science Subsystem - NASA Planetary Data System |url=https://arcnav.psi.edu/urn:nasa:pds:context:instrument:iss.mr9  |access-date=2025-02-27 |website=arcnav.psi.edu}}</ref> 

The instrument provided the first global mapping of Mars' surface; discovered volcanoes, valleys, and dried riverbeds, suggesting past water activity; captured dust storms covering the entire planet and mapped Phobos and Deimos, Mars' two moons.

== Spacecraft and subsystems ==
The [[Electric power|power]] for the [[spacecraft]] was provided by a total of 14,742 solar cells, being distributed between 4 [[Solar panels on spacecraft|solar panels]], which in total resulted in 7.7 meters of solar panels being present in the spacecraft. The solar panels produced 500 [[Watt|watts]] in the orbit of [[Mars]]. The energy was stored in a 20 amp-hr nickel-cadmium [[Electric battery|battery]].<ref name=nssdc1/>

[[Propulsion]] was provided by the RS-2101a engine, which could produce 1340 [[Newton (unit)|N]] thrust, and in total could have 5 restarts. The engine was fueled by [[Monomethylhydrazine|monomethyl hydrazine]] and [[Dinitrogen tetroxide|nitrogen tetroxide]]. For [[Spacecraft attitude control|attitude control]], the spacecraft contained 2 sets of 6 [[nitrogen]] jets on the tip of the solar panels. Attitude knowledge was provided by a [[Sun sensor]], a Canopus star tracker, [[Gyroscope|gyroscopes]], an inertial reference unit, and an [[accelerometer]]. The [[Spacecraft thermal control|thermal control]] was achieved by the use of louvers on the eight sides of the frame and thermal blankets.<ref name=nssdc1/>

== Achievements ==
[[File:M09 mtvs4187 45.gif|thumb|right|Mariner 9 view of the [[Noctis Labyrinthus]] "labyrinth" at the western end of [[Valles Marineris]].]]

Mariner 9 was the first [[spacecraft]] to [[orbit]] another [[planet]]. It carried an instrument payload similar to Mariners 6 and 7, but because of the need for a larger propulsion system to control the spacecraft in Martian orbit, it weighed more than Mariners 6 and 7 combined (Mariner 6 and Mariner 7 weighed 413 kilograms while Mariner 9 weighed 997.9 kilograms).{{r|nasa3|nasa1}} When Mariner 9 arrived at Mars on November 10, 1971, [[Planetary science|planetary scientists]] were surprised (although had anticipated during perihelic opposition) to find the [[celestial body's atmosphere|atmosphere]] was thick with "a planet-wide robe of [[Martian soil#Atmospheric dust|dust]], the largest [[Climate of mars#Dust storms|storm]] ever observed."<ref name=nssdc1/> The surface was totally obscured. On November 14 1971 after slowing down, Mariner 9's computer was thus reprogrammed from Earth to delay imaging of the surface for a couple of months until the dust settled. Closing down the camera in order to save energy. The main surface imaging did not get underway until mid-January 1972.  However, surface-obscured images did contribute to the collection of Mars science, including understanding of the existence of several huge high-altitude volcanoes of the [[Tharsis Bulge]] that gradually became visible as the dust storm abated.  This unexpected situation made a strong case for the desirability of studying a planet from orbit rather than merely flying past.<ref name=Pyle2012/> It also highlighted the importance of flexible mission software. The Soviet Union's [[Mars 2]] and [[Mars 3]] probes, which arrived during the same dust storm, were unable to adapt to the unexpected conditions having been preprogrammed, which severely limited the amount of data that they were able to collect.
[[File:Mariner 9 - Olympus Mons Caldera (39210604190).png|thumb|Mariner 9 narrow angle camera of Olympus Mons' central caldera. This image was among the first images to confirm that Olympus Mons was a volcano - the largest known in the Solar System.]]
After 349 days in orbit, Mariner 9 had transmitted 7,329 images, covering 85% of Mars' surface, whereas previous flyby missions had returned less than one thousand images covering only a small portion of the planetary surface.<ref name=nasa1/> 
The images revealed [[river]] beds, [[Impact crater|crater]]s, massive extinct [[volcano]]es (such as [[Olympus Mons]], the largest known volcano in the [[Solar System]]; Mariner 9 led directly to its reclassification from Nix Olympica), [[canyon]]s (including the [[Valles Marineris]], a system of canyons over about {{convert|2500|mi|km|-1|order=flip}} long), evidence of wind [[erosion]] and deposition, weather fronts, [[fog]]s, and more.<ref name=space.com1/> Mars' small [[natural satellite|moon]]s, [[Phobos (moon)|Phobos]] and [[Deimos (moon)|Deimos]], were also photographed.{{r|nasa2|nasa4}}

The findings from the Mariner 9 mission underpinned the later [[Viking program]].<ref name=Pyle2012/>

The enormous Valles Marineris canyon system is named after Mariner 9 in honor of its achievements.<ref name=Pyle2012/>

After depleting its supply of [[Spacecraft attitude control|attitude control]] gas, the spacecraft was turned off on October 27, 1972.<ref name=Pyle2012/>

== Construction ==
[[File:Mariner 8 diagram.jpg|thumb|A schematic of Mariner 8/9, showing the major components and features]]
The [[ultraviolet]] [[spectrometer]] (UVS) aboard Mariner 9 was constructed by the [[Laboratory for Atmospheric and Space Physics]] at the [[University of Colorado at Boulder|University of Colorado]], [[Boulder, Colorado]].<ref name=nssdc2/> The ultraviolet spectrometer team was led by Professor Charles Barth.

The Infrared Interferometer Spectrometer (IRIS) team was led by Dr. Rudolf A. Hanel from [[NASA Goddard Spaceflight Center]] (GSFC).<ref name=nssdc3/> The IRIS instrument was built by [[Texas Instruments]], [[Dallas, Texas]].

The Infrared Radiometer (IRR) team was led by Professor Gerald Neugebauer from the [[California Institute of Technology]] (Caltech).<ref name=nssdc4/>

== Error-correction codes achievements ==
[[File:Hadamard-Code.svg|thumb|Matrix of the Hadamard code (32, 6, 16) for the Reed-Muller Code (1, 5) of the NASA space probe Mariner 9]]To control for errors in the reception of the [[grayscale]] image data sent by Mariner 9 (caused by a low [[signal-to-noise ratio]]), the data had to be encoded before transmission using a so-called [[forward error correction|forward error-correcting code]] (FEC). Without FEC, noise would have made up roughly a quarter of a received image, while the FEC encoded the data in a redundant way which allowed for the reconstruction of most of the sent image data at reception.

Since the flown hardware was constrained with regards to weight, power consumption, storage, and computing power, some considerations had to be put into choosing an FEC, and it was decided to use a [[Hadamard code]] for Mariner 9. Each image pixel was represented as a six-bit binary value, which had 64 possible grayscale levels. Because of limitations of the transmitter, the maximum useful data length was about 30 bits. Instead of using a [[repetition code]], a [32, 6, 16] Hadamard code was used, which is also a 1st-order [[Reed-Muller code]]. Errors of up to seven bits per each 32-bit word could be corrected using this scheme.<ref name=youtube1/><ref name=youtube2/> Compared to a five-repetition code, the error correcting properties of this Hadamard code were much better, yet its data rate was comparable. The efficient decoding [[algorithm]] was an important factor in the decision to use this code. The circuitry used was called the "Green Machine", which employed the [[fast Fourier transform]], increasing the decoding speed by a factor of three.<ref name=denver/>

== Present location ==
{{Update section|date=April 2023}}
Mariner 9 remained in orbit around Mars after its operational use. Today it is thought Mariner 9 either burnt up on entry of the martian atmosphere or impacted the surface. 

NASA had provided multiple dates for when Mariner 9 could enter the Martian atmosphere. At the time of the mission, Mariner 9 was left in an orbit that would not decay for at least 50 years. <ref name="nssdc1" /> In 2011, NASA predicted that Mariner 9 would burn up or crash into Mars around 2022.<ref name=nasa5/> However, a 2018 revision to the Mariner 9 mission page by NASA expected Mariner 9 would crash into Mars "sometime around 2020".<ref name=nasa1/>  

== See also ==
{{Portal|Spaceflight}}
* [[Exploration of Mars]]
* [[List of Mars orbiters]]
* [[List of missions to Mars]]
* [[Space exploration]]
* [[Timeline of artificial satellites and space probes]]
* [[Uncrewed space mission]]s
* [[Mars flyby]]

== References ==
{{Reflist|refs=

<ref name="denver">{{cite web
| url= http://www-math.ucdenver.edu/~wcherowi/courses/m7409/mariner9talk.pdf
| archive-url= https://web.archive.org/web/20130927082620/http://www-math.ucdenver.edu/~wcherowi/courses/m7409/mariner9talk.pdf
| archive-date= 27 September 2013
| title= Combinatorics in Space The Mariner 9 Telemetry System }}
</ref>

<ref name="final_report">{{cite web
| url= https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730018117_1973018117.pdf
| archive-url= https://web.archive.org/web/20100527091624/https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730018117_1973018117.pdf
| archive-date= 27 May 2010
| url-status= dead
| title= Mariner Mars 1971 Project Final Report
| publisher= [[NASA]]
| access-date= 28 December 2011 }}
</ref>

<ref name="nasa1">{{cite web
| url= https://science.nasa.gov/mission/mariner-9/ 
| title= Mariner 9 - NASA Science
| website= science.nasa.gov
| date= 20 December 2017
| publisher= [[NASA]]
| access-date= 28 September 2023 }}
</ref>

<ref name="nasa2">{{Cite web
| url= https://science.nasa.gov/planetary-science/programs/mars-exploration/ 
| title= Mars Exploration - NASA Science
| website= science.nasa.gov
| date= 27 February 2008
| publisher= [[NASA]] 
| access-date= 12 December 2011 }}
</ref>

<ref name="nasa3">{{Cite web
| title= Mariner 8 (Mariner H) - Mars Missions
| url= https://www.jpl.nasa.gov/missions/mariner-8-mariner-h
| website= jpl.nasa.gov
| publisher= [[NASA]] / [[Jet Propulsion Laboratory|JPL]]
| access-date= 20 December 2023 }}
</ref>

<ref name="nasa4">{{cite book
| author1= W. K. Hartmann
| author2= O. Raper
| date= 1974
| title= The New Mars: The Discoveries of Mariner 9
| url= https://ntrs.nasa.gov/citations/19750005657
| id= SP-337
| publisher= [[NASA]] }}
</ref>

<ref name="nasa5">{{Cite web
| title= This Month in NASA History: Mariner 9
| url= https://appel.nasa.gov/2011/11/27/ata_4-9_mariner_9-html/
| access-date= 21 February 2022
| website= appel.nasa.gov
| date= 27 November 2011
| publisher= [[NASA]] }}
</ref>

<ref name="nssdc1">{{cite web
| url= https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1971-051A 
| title= Mariner 9
| website= nssdc.gsfc.nasa.gov
| publisher= [[NASA]]
| access-date= 28 December 2011 }} {{source-attribution}}
</ref>

<ref name="nssdc2">{{Cite web
| author1= Charles Barth
| title= Mariner 9: Ultraviolet Spectrometer (UVS) 
| url= https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1971-051A-02
| access-date= 23 February 2024
| website= nssdc.gsfc.nasa.gov
| publisher= [[NASA]] }}
</ref>

<ref name="nssdc3">{{Cite web 
| title= Mariner 9: Infrared Interferometer Spectrometer (IRIS) 
| url= https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1971-051A-03
| access-date= 23 February 2024
| website= nssdc.gsfc.nasa.gov
| publisher= [[NASA]] }}
</ref>

<ref name="nssdc4">{{Cite web
| title= Mariner 9: Infrared Radiometer (IRR)
| url= https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1971-051A-01
| access-date= 23 February 2024
| website= nssdc.gsfc.nasa.gov
| publisher= [[NASA]] }}
</ref>

<ref name="Pyle2012">{{cite book
| author1= Rod Pyle
| title= Destination Mars: New Explorations of the Red Planet
| date= 2012
| publisher= [[Prometheus Books]]
| isbn= 978-1-61614-589-7
| pages= 73–78 }}
</ref>

<ref name="space.com1">{{Cite web
| author1= Elizabeth Howell
| url= https://www.space.com/18439-mariner-9.html
| title= Mariner 9: First Spacecraft to Orbit Mars
| website= Space.com
| date= 8 November 2018 }}
</ref>

<ref name="youtube1">{{YouTube 
| id= NRv3HMEyuDE
| title= 64 Shades of Martian Grey }}
</ref>

<ref name="youtube2">{{YouTube 
| id= CtOCqKpti7s
| title= Reed-Muller Code (64 Shades of Grey pt2) }}
</ref>
}}

== External links ==
{{commonscat|Mariner 9}}
*[https://web.archive.org/web/20120731101459/http://solarsystem.nasa.gov/missions/profile.cfm?MCode=Mariner_09 Mariner 9 Mission Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
*[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1971-051A NSSDC Master Catalog: Spacecraft – Mariner 9]
*[https://web.archive.org/web/20120211142601/http://sse.jpl.nasa.gov/missions/profile.cfm?Sort=Target&Target=Mars&MCode=Mariner_09 NASA-JPL Guide to Mariner 9]
*[https://www.flickr.com/photos/46043736@N03/sets/72157623202452236/with/4268348665/ some Mariner 9 images of Mars]
*[http://planetary.org/blog/article/00003296/ Mariner 9 approaching Mars movie] {{Webarchive|url=https://web.archive.org/web/20120125055707/http://planetary.org/blog/article/00003296/ |date=2012-01-25 }}
*[http://petermasek.tripod.com/mariner9.html Mariner 9 images, including dust storm]
*[http://www.planetary.org/multimedia/space-images/mars/phobos-from-mariner-9.html Mariner 9 view of Phobos] (hosted by The Planetary Society)
*[http://photojournal.jpl.nasa.gov/catalog/PIA02304 Mariner 9 image compared to MGS image, helps determine if Dunes moved in decades]
*[https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730002410.pdf P.418  Correct DN values appear to be 512, not 64  i.e. 9bits per pixel]

{{Mariner program | before=[[Mariner 8]] | after=[[Mariner 10]] }}
{{Mars spacecraft}}
{{Satellite and spacecraft instruments}}
{{Orbital launches in 1971}}

[[Category:Mariner program]]
[[Category:Missions to Mars]]
[[Category:1971 in spaceflight]]
[[Category:Derelict satellites orbiting Mars]]
[[Category:Derelict space probes]]
[[Category:Spacecraft launched by Atlas-Centaur rockets]]
[[Category:Spacecraft launched in 1971]]
[[Category:Geography of Mars]]