Editing Phobos (moon) (section)

== Physical characteristics ==
[[File:Moon_Phobos_Deimos.png|left|thumb|Size comparison between Phobos, Deimos and the [[Moon]] (right)]]
Phobos has dimensions of {{convert|26 × 23 × 18|km}},<ref name="Ernst2023"/> and retains too little mass to be rounded under its own gravity. Phobos does not have an [[atmosphere]] due to its low mass and low gravity.<ref>{{cite web |url=http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mar_Phobos |title=Solar System Exploration: Planets: Mars: Moons: Phobos: Overview |publisher=Solarsystem.nasa.gov |access-date=19 August 2013 |url-status=dead |archive-url=https://web.archive.org/web/20140624191709/https://solarsystem.nasa.gov/planets/profile.cfm?Object=Mar_Phobos |archive-date=24 June 2014 }}</ref> It is one of the least reflective bodies in the Solar System, with an albedo of about 0.071.<ref name="jplssd">{{cite web |url=http://ssd.jpl.nasa.gov/?sat_phys_par |publisher=[[JPL]] (Solar System Dynamics) |title=Planetary Satellite Physical Parameters |date=13 July 2006 |access-date=29 January 2008 }}</ref> Infrared spectra show that it has carbon-rich material found in [[carbonaceous chondrites]], and its composition shows similarities to that of Mars' surface.<ref>{{Cite journal |last1=Citron |first1=R. I. |last2=Genda |first2=H. |last3=Ida |first3=S. |date=2015 |title=Formation of Phobos and Deimos via a giant impact |url= |journal=Icarus |language=en |volume=252 |pages=334–338 |arxiv=1503.05623 |doi=10.1016/j.icarus.2015.02.011|bibcode=2015Icar..252..334C }}</ref> Phobos's density is too low to be solid rock, and it is known to have significant [[porosity]].<ref>{{cite web |title=Porosity of Small Bodies and a {{sic|nolink=y|reason=error in source|Reassesment}} of Ida's Density |url=http://www.aas.org/publications/baas/v31n4/dps99/65.htm |quote=When the error bars are taken into account, only one of these, Phobos, has a porosity below 0.2... |url-status=dead |archive-url=https://web.archive.org/web/20070926224539/http://www.aas.org/publications/baas/v31n4/dps99/65.htm |archive-date=26 September 2007 }}</ref><ref name="Close Inspection for Phobos">{{cite web |title=Close Inspection for Phobos |url=http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=31031 |quote=It is light, with a density less than twice that of water, and orbits just {{Convert|5989|km|sp=us}} above the Martian surface. }}</ref><ref>{{Cite journal |last1=Busch |first1=Michael W. |display-authors=4 |last2=Ostro |first2=Steven J. |last3=Benner |first3=Lance A. M. |last4=Giorgini |first4=Jon D. |last5=Magri |first5=Christopher |last6=Howell |first6=Ellen S. |last7=Nolan |first7=Michael C. |last8=Hine |first8=Alice A. |last9=Campbell |first9=Donald B. |last10=Shapiro |first10=Irwin I. |last11=Chandler |first11=John F. |date=2007 |title=Arecibo Radar Observations of Phobos and Deimos |journal=Icarus |volume=186 |issue=2 |pages=581–584 |doi=10.1016/j.icarus.2006.11.003 |bibcode=2007Icar..186..581B }}</ref> These results led to the suggestion that Phobos might contain a substantial reservoir of ice. Spectral observations indicate that the surface [[regolith]] layer lacks hydration,<ref>{{Cite journal |last1=Murchie |first1=Scott L. |display-authors=4 |last2=Erard |first2=Stephane |last3=Langevin |first3=Yves |last4=Britt |first4=Daniel T. |last5=Bibring |first5=Jean-Pierre |last6=Mustard |first6=John F. |last7=Head |first7=James W. |last8=Pieters |first8=Carle M. |title=Disk-resolved Spectral Reflectance Properties of Phobos from 0.3–3.2 microns: Preliminary Integrated Results from PhobosH 2 |journal=Abstracts of the Lunar and Planetary Science Conference |volume=22 |page=943 |date=1991 |bibcode=1991pggp.rept..249M }}</ref><ref>{{Cite journal |last1=Rivkin |first1=Andrew S. |display-authors=4 |last2=Brown |first2=Robert H. |last3=Trilling |first3=David E. |last4=Bell III |first4=James F. |last5=Plassmann |first5=Joseph (Joe) H. |date=March 2002 |title=Near-Infrared Spectrophotometry of Phobos and Deimos |journal=Icarus |volume=156 |issue=1 |pages=64–75 |bibcode=2002Icar..156...64R |doi=10.1006/icar.2001.6767 }}</ref> but ice below the regolith is not ruled out.<ref>{{cite journal |last1=Fanale |first1=Fraser P. |first2=James R. |last2=Salvail |date=1989 |title=Loss of water from Phobos |journal=Geophys. Res. Lett. |volume=16 |number=4 |pages=287–290 |doi=10.1029/GL016i004p00287 |bibcode=1989GeoRL..16..287F }}</ref><ref>{{cite journal |title=Evolution of the water regime of Phobos |first1=Fraser P. |last1=Fanale |first2=James R. |last2=Salvail |doi = 10.1016/0019-1035(90)90089-R |date=Dec 1990 |journal=Icarus |volume=88 |issue=2 |pages=380–395 |bibcode=1990Icar...88..380F }}</ref> Surface temperatures range from about {{convert|−4|C|F}} on the sunlit side to {{convert|−112|C|F}} on the shadowed side.<ref name="phobos">{{cite web |title=NASA – Phobos |url=http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mar_Phobos |url-status=dead |archive-url=https://web.archive.org/web/20140624191709/https://solarsystem.nasa.gov/planets/profile.cfm?Object=Mar_Phobos |archive-date=24 June 2014 |access-date=4 August 2014 |publisher=Solarsystem.nasa.gov}}</ref>

Unlike Deimos, Phobos is heavily cratered,<ref>{{cite web |url=http://www.bbc.co.uk/science/space/solarsystem/mars/phobos.shtml |title=Phobos |work=[[BBC Online]] |archive-url=https://web.archive.org/web/20090422160500/http://www.bbc.co.uk/science/space/solarsystem/mars/phobos.shtml |archive-date=22 April 2009 |date=12 January 2004 |access-date=19 July 2021 |url-status=dead}}</ref> with one of the craters near the equator having a central peak despite the moon's small size.<ref>{{cite magazine |url=https://books.google.com/books?id=Q6tkzO06q4oC&pg=PA158 |title=Viking looks at Phobos in detail |magazine=[[New Scientist]] |volume=72 |issue=1023 |page=158 |publisher=[[Reed Business Information]] |date=21 October 1976 |access-date=19 July 2021 |id={{ISSN|0262-4079}} |via=[[Google Books]]}}</ref> The most prominent of these is the crater [[Stickney (crater)|Stickney]], an impact crater {{Convert|9|km|mi|abbr=on}} in diameter, which takes up a substantial proportion of the moon's surface area. As with the [[Saturn]]ian moon [[Mimas (moon)|Mimas]]'s crater [[Herschel (Mimantean crater)|Herschel]], the impact that created Stickney probably almost shattered Phobos.<ref>{{cite web |title=Stickney Crater-Phobos |url=http://www.solarviews.com/cap/mars/phobos2.htm |quote=One of the most striking features of Phobos, aside from its irregular shape, is its giant crater Stickney. Because Phobos is only {{Convert|28|by|20|km||sp=us}}, it must have been nearly shattered from the force of the impact that caused the giant crater. Grooves that extend across the surface from Stickney appear to be surface fractures caused by the impact. }}</ref>

{{multiple image
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| footer            = (''top'') False color image of the impact crater [[Stickney (crater)|Stickney]] imaged by the ''[[Mars Reconnaissance Orbiter]]'' in March 2008; (''bottom'') Labeled Map of Phobos – Moon of Mars (U.S. Geological Survey)
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Many grooves and streaks cover the oddly shaped surface. The grooves are typically less than {{Convert|30|m|sp=us}} deep, {{Convert|100|to|200|m|sp=us}} wide, and up to {{Convert|20|km|sp=us}} in length, and were originally assumed to have been the result of the same impact that created Stickney. Analysis of results from the ''[[Mars Express]]'' spacecraft revealed that the grooves are not radial to Stickney, but are centered on the leading apex of Phobos in its orbit (which is not far from Stickney). Researchers suspected that they had been excavated by material ejected into space by impacts on the surface of Mars. The grooves thus formed as [[crater chain]]s, and all of them fade away as the trailing apex of Phobos is approached. They have been grouped into 12 or more families of varying age, presumably representing at least 12 Martian impact events.<ref name="grooves origin">{{cite web |title=New Evidence on the Origin of Phobos' Parallel Grooves from HRSC Mars Express |last1=Murray |first1=John B. |display-authors=4 |first2=John B. |last2=Murray |first3=Jonathan C. |last3=Iliffe |first4=Jan-Peter A. L. |last4=Muller |first5=Gerhard |last5=Neukum |first6=Stephanie |last6=Werner |first7=Matt |last7=Balme |last8=HRSC Co-Investigator Team |publisher=37th Annual Lunar and Planetary Science Conference, March 2006 |url=http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2195.pdf }}</ref> In November 2018, based on computational probability analysis, astronomers concluded that the many grooves on Phobos were caused by boulders ejected from the asteroid impact that created Stickney crater. These boulders rolled in a predictable pattern on the surface of the moon.<ref name="UT-20181120">{{cite web |last=Gough |first=Evan |title=Strange Grooves on Phobos Were Caused by Boulders Rolling Around on its Surface |url=https://www.universetoday.com/140593/strange-grooves-on-phobos-were-caused-by-boulders-rolling-around-on-its-surface/ |date=20 November 2018 |work=[[Universe Today]] |access-date=21 November 2018 }}</ref><ref name="PSS-20181116">{{cite journal |last1=Ramsley |first1=Kenneth R. |last2=Head |first2=James W. |title=Origin of Phobos grooves: Testing the Stickney Crater ejecta model |journal=[[Planetary and Space Science]] |volume=165 |pages=137–147 |doi=10.1016/j.pss.2018.11.004 |bibcode=2019P&SS..165..137R |year=2019 |s2cid=86859432 }}</ref>

Faint dust rings produced by Phobos and Deimos have long been predicted but attempts to observe these rings have, to date, failed.<ref>{{Cite journal |doi=10.1016/j.pss.2006.05.009 |last1=Showalter |first1=Mark R. |last2=Hamilton |first2=Douglas P. |last3=Nicholson |first3=Philip D. |title=A Deep Search for Martian Dust Rings and Inner Moons Using the Hubble Space Telescope |journal=Planetary and Space Science |volume=54 |date=2006 |issue=9–10 |pages=844–854 |url=http://www.astro.umd.edu/~hamilton/research/reprints/ShoHamNic06.pdf |bibcode=2006P&SS...54..844S }}</ref> Images from ''[[Mars Global Surveyor]]'' indicate that Phobos is covered with a layer of fine-grained regolith at least 100 meters thick; it is hypothesized to have been created by impacts from other bodies, but it is not known how the material stuck to an object with almost no gravity.<ref>{{cite web |last=Britt |first=Robert Roy |title=Forgotten Moons: Phobos and Deimos Eat Mars' Dust |url=http://www.space.com/scienceastronomy/forgotten_moons_010313-3.html |publisher=space.com |date=13 March 2001 |access-date=12 May 2010 }}</ref>

The unique [[Kaidun meteorite]] that fell on a [[Soviet Union|Soviet]] military base in [[Yemen]] in 1980 has been hypothesized to be a piece of Phobos, but this could not be verified because little is known about the exact composition of Phobos.<ref>{{Cite journal |last=Ivanov |first=Andrei V. |bibcode=2004SoSyR..38...97I |title=Is the Kaidun Meteorite a Sample from Phobos? |date=March 2004 |journal=Solar System Research |volume=38 |issue=2 |pages=97–107 |doi=10.1023/B:SOLS.0000022821.22821.84 |s2cid=123669722 }}</ref><ref>{{Cite journal |last1=Ivanov |first1=Andrei |first2=Michael |last2=Zolensky |title=The Kaidun Meteorite: Where Did It Come From? |url=http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1236.pdf |journal=Lunar and Planetary Science |date=2003 |volume=34 |quote=The currently available data on the lithologic composition of the Kaidun meteorite– primarily the composition of the main portion of the meteorite, corresponding to CR2 carbonaceous chondrites and the presence of clasts of deeply differentiated rock&nbsp;– provide weighty support for considering the meteorite’s parent body to be a carbonaceous chondrite satellite of a large differentiated planet. The only possible candidates in the modern Solar System are Phobos and Deimos, the moons of Mars. }}</ref>

=== Shklovsky's "Hollow Phobos" hypothesis ===
In the late 1950s and 1960s, the unusual orbital characteristics of Phobos led to speculations that it might be hollow.<ref>{{cite web |date=12 July 2017 |title=A Convenient Truth - One Universe at a Time |url=https://archive.briankoberlein.com/2017/07/12/a-convenient-truth/index.html |access-date=14 July 2020}}</ref> Around 1958, Russian astrophysicist [[Iosif Samuilovich Shklovsky]], studying the [[Secular phenomena|secular]] [[acceleration]] of Phobos's orbital motion, suggested a "thin sheet metal" structure for Phobos, a suggestion which led to speculations that Phobos was of artificial origin.<ref name="Shklovsky">Shklovsky, Iosif Samuilovich; ''The Universe, Life, and Mind'', Academy of Sciences USSR, Moscow, 1962</ref> Shklovsky based his analysis on estimates of the upper Martian atmosphere's density, and deduced that for the weak braking effect to be able to account for the secular acceleration, Phobos had to be very light—one calculation yielded a hollow iron sphere {{Convert|16|km|sp=us}} across but less than {{convert|6|cm}} thick.<ref name="Shklovsky" /><ref>{{Cite journal |last=Öpik |first=Ernst Julius |author-link=Ernst Julius Öpik |date=September 1964 |title=Is Phobos Artificial? |journal=Irish Astronomical Journal |volume=6 |pages=281–283 |bibcode=1964IrAJ....6..281.}}</ref> In a February 1960 letter to the journal ''Astronautics'',<ref name="Singer">[[Fred Singer|Singer, S. Fred]]; ''Astronautics'', February 1960</ref> [[Fred Singer]], then science advisor to U.S. President [[Dwight D. Eisenhower]], said of Shklovsky's theory:
<blockquote>If the satellite is indeed spiraling inward as deduced from astronomical observation, then there is little alternative to the hypothesis that it is hollow and therefore Martian made. The big 'if' lies in the astronomical observations; they may well be in error. Since they are based on several independent sets of measurements taken decades apart by different observers with different instruments, systematic errors may have influenced them.<ref name="Singer" /></blockquote>

Subsequently, the systematic data errors that Singer predicted were found to exist, the claim was called into doubt,<ref name="Öpik1963">{{Cite journal |last=Öpik |first=Ernst Julius |date=March 1963 |title=News and Comments: Phobos, Nature of Acceleration |journal=Irish Astronomical Journal |volume=6 |page=40 |bibcode=1963IrAJ....6R..40.}}</ref> and accurate measurements of the orbit available by 1969 showed that the discrepancy did not exist.<ref>{{Citation |last=Singer |first=S. Fred |title=On the Origin of the Martian Satellites Phobos and Deimos |date=1967 |journal=The Moon and the Planets |pages=317 |bibcode=1967mopl.conf..317S}}</ref> Singer's critique was justified when earlier studies were discovered to have used an overestimated value of {{convert|5|cm}} per year for the rate of altitude loss, which was later revised to {{convert|1.8|cm}} per year.<ref>Singer, S. Fred; "More on the Moons of Mars", ''Astronautics'', February 1960. [[American Astronautical Society]], page 16</ref> The secular acceleration is now attributed to tidal effects, which create drag on the moon and therefore cause it to spiral inward.<ref name="JGR-Planets">{{cite news |last1=Efroimsky |first1=Michael |last2=Lainey |first2=Valéry |date=29 December 2007 |title=Physics of bodily tides in terrestrial planets and the appropriate scales of dynamical evolution |work=Journal of Geophysical Research—Planets|volume=112|page=E12003 |doi=10.1029/2007JE002908}}</ref>

The density of Phobos has now been directly measured by spacecraft to be {{convert|1.887| g/cm3||abbr=on}}.<ref name="dlr2008">{{cite web |date=16 October 2008 |title=Mars Express closes in on the origin of Mars' larger moon |url=http://www.dlr.de/mars/en/desktopdefault.aspx/tabid-207/422_read-13776/ |access-date=16 October 2008 |publisher=[[German Aerospace Center|DLR]] |archive-date=4 June 2011 |archive-url=https://web.archive.org/web/20110604233019/http://www.dlr.de/mars/en/desktopdefault.aspx/tabid-207/422_read-13776/ |url-status=dead }}</ref> Current observations are consistent with Phobos being a [[rubble pile]].<ref name="dlr2008" /> Images obtained by the [[Viking probes|''Viking'' probes]] in the 1970s showed a natural object, not an artificial one. Nevertheless, mapping by the ''Mars Express'' probe and subsequent volume calculations do suggest the presence of voids and indicate that it is not a solid chunk of rock but a porous body.<ref>Clark, Stuart; "Cheap Flights to Phobos" in ''New Scientist'' magazine, 30 January 2010</ref> The porosity of Phobos was calculated to be 30% ± 5%, or a quarter to a third being empty.<ref name="Andert" />

=== Named geological features ===

Geological features on Phobos are named after [[astronomer]]s who studied Phobos and people and places from [[Jonathan Swift]]'s ''[[Gulliver's Travels]]''.<ref>[http://planetarynames.wr.usgs.gov/append6.html Gazetteer of Planetary Nomenclature] [[USGS]] Astrogeology Research Program, Categories</ref>
{{clear right}}

==== {{anchor|Craters on Phobos}} Craters on Phobos ====
Some craters have been named, and are listed in the following map and table.<ref>[http://planetarynames.wr.usgs.gov/jsp/FeatureTypes2.jsp?system=Mars&body=Phobos&systemID=4&bodyID=22&sort=AName&show=Fname&show=Lat&show=Long&show=Diam&show=Stat&show=Orig Gazetteer of Planetary Nomenclature] [[USGS]] Astrogeology Research Program, Craters</ref>
{{PhobosCraterNames}}
{| class="wikitable" 
! [[impact crater|Crater]] !! width=90pt| Coordinates !! [[Diameter]]<br>(km) !! Approval<br>Year !! class="unsortable" | [[Eponym]] !! Ref 
|-id="Clustril"
| Clustril || {{Coord|60|N|91|W|globe:phobos_type:landmark|name=Clustril}} || align=right | 3.4 || align=center | 2006 || Character in [[Lilliput and Blefuscu|Lilliput]] who informed [[Flimnap, the Lilliputian Premier|Flimnap]] that his wife had visited Gulliver privately in Jonathan Swift's novel ''[[Gulliver's Travels]]'' || {{WGPSN|14257}}
|-id="D'Arrest"
| D'Arrest || {{Coord|39|S|179|W|globe:phobos_type:landmark|name=D'Arrest}} || align=right | 2.1 || align=center | 1973 || [[Heinrich Louis d'Arrest]]; German/Danish astronomer (1822–1875) || {{WGPSN|1696}}
|-id="Drunlo"
| Drunlo || {{Coord|36.5|N|92|W|globe:phobos_type:landmark|name=Drunlo}} || align=right | 4.2 || align=center | 2006 || Character in Lilliput who informed Flimnap that his wife had visited Gulliver privately in ''Gulliver's Travels'' || {{WGPSN|14258}}
|-id="Flimnap"
| Flimnap || {{Coord|60|N|10|E|globe:phobos_type:landmark|name=Flimnap}} || align=right | 1.5 || align=center | 2006 || Treasurer of Lilliput in ''Gulliver's Travels'' || {{WGPSN|14259}}
|-id="Grildrig"
| Grildrig || {{Coord|81|N|165|E|globe:phobos_type:landmark|name=Grildrig}} || align=right | 2.6 || align=center | 2006 || Name given to Gulliver by the farmer's daughter [[Glumdalclitch]] in the giants' country [[Brobdingnag]] in ''Gulliver's Travels'' || {{WGPSN|14260}}
|-id="Gulliver"
| Gulliver || {{Coord|62|N|163|W|globe:phobos_type:landmark|name=Gulliver}} || align=right | 5.5 || align=center | 2006 || [[Lemuel Gulliver]]; surgeon captain and voyager in ''Gulliver's Travels'' || {{WGPSN|14261}}
|-id="Hall"
| Hall || {{Coord|80|S|150|E|globe:phobos_type:landmark|name=Hall}} || align=right | 5.4 || align=center | 1973 || [[Asaph Hall]]; American astronomer discoverer of Phobos and Deimos (1829–1907) || {{WGPSN|2328}}
|-id="Limtoc"
| [[Limtoc]] || {{Coord|11|S|54|W|globe:phobos_type:landmark|name=Limtoc}} || align=right | 2 || align=center | 2006 || General in Lilliput who prepared articles of impeachment against Gulliver in ''Gulliver's Travels'' || {{WGPSN|14262}}
|-id="Öpik"
| Öpik || {{Coord|7|S|63|E|globe:phobos_type:landmark|name=Öpik}} || align=right | 2 || align=center | 2011 || [[Ernst J. Öpik]], Estonian astronomer (1893–1985) || {{WGPSN|14865}}
|-id="Reldresal"
| Reldresal || {{Coord|41|N|39|W|globe:phobos_type:landmark|name=Reldresal}} || align=right | 2.9 || align=center | 2006 || Secretary for Private Affairs in Lilliput; Gulliver's friend in ''Gulliver's Travels'' || {{WGPSN|14263}}
|-id="Roche"
| Roche || {{Coord|53|N|177|E|globe:phobos_type:landmark|name=Roche}} || align=right | 2.3 || align=center | 1973 || [[Édouard Roche]]; French astronomer (1820–1883) || {{WGPSN|5167}}
|-id="Sharpless"
| Sharpless || {{Coord|27.5|S|154|W|globe:phobos_type:landmark|name=Sharpless}} || align=right | 1.8 || align=center | 1973 || [[Bevan Sharpless]]; American astronomer (1904–1950) || {{WGPSN|5474}}
|-id="Shklovsky"
| Shklovsky || {{Coord|24|N|112|E|globe:phobos_type:landmark|name=Shklovsky}} || align=right | 2 || align=center | 2011 || [[Iosif Shklovsky]], Soviet astronomer (1916–1985) || {{WGPSN|14866}}
|-id="Skyresh"
| Skyresh || {{Coord|52.5|N|40|E|globe:phobos_type:landmark|name=Skyresh}} || align=right | 1.5 || align=center | 2006 || Skyresh Bolgolam; High Admiral of the Lilliput council who opposed Gulliver's plea for freedom and accused him of being a traitor in ''Gulliver's Travels'' || {{WGPSN|14264}}
|-id="Stickney"
| [[Stickney (crater)|Stickney]] || {{Coord|1|N|49|W|globe:phobos_type:landmark|name=Stickney}} || align=right | 9 || align=center | 1973 || [[Angeline Stickney]] (1830–1892); wife of American astronomer Asaph Hall (above) || {{WGPSN|5707}}
|-id="Todd"
| Todd || {{Coord|9|S|153|W|globe:phobos_type:landmark|name=Todd}} || align=right | 2.6 || align=center | 1973 || [[David Peck Todd]]; American astronomer (1855–1939) || {{WGPSN|6042}}
|-id="Wendell"
| Wendell || {{Coord|1|S|132|W|globe:phobos_type:landmark|name=Wendell}} || align=right | 1.7 || align=center | 1973 || [[Oliver Wendell]]; American astronomer (1845–1912) || {{WGPSN|6518}}
|}{{clear}}

==== Other named features ====
There is one named [[Planetary geology#Regio (astronomy)|regio]], ''Laputa Regio'', and one named [[planitia]], ''Lagado Planitia''; both are named after places in ''Gulliver's Travels'' (the fictional [[Gulliver's Travels#Part III: A Voyage to Laputa, Balnibarbi, Luggnagg, Glubbdubdrib and Japan|Laputa]], a flying island, and [[Lagado]], imaginary capital of the fictional nation [[Balnibarbi]]).<ref>[http://planetarynames.wr.usgs.gov/Page/PHOBOS/target Gazetteer of Planetary Nomenclature] [[USGS]] Astrogeology Research Program, Phobos</ref> The only named ridge on Phobos is ''Kepler Dorsum'', named after the astronomer [[Johannes Kepler]].<ref>{{cite journal |title=Working Group for Planetary System Nomenclature (Groupe de Travail Pour la Nomenclature du Systeme Planetaire) |journal=Transactions of the International Astronomical Union |date=1988 |volume=20 |issue=2 |page=372 |doi=10.1017/S0251107X0002767X|doi-access=free }}</ref>