Montes Rook

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Montes Rook

(formerly Rook Mts)

Lat: 19.3°S, Long: 94.6°W, Diam: 460-655 km(see note), Height: 6 km, Rükl: 50

external image normal_Rook-Cordillera_rings_LO-IV-187M_LTVT.JPG
LO-IV-187M The circles superimposed on this Lunar Orbiter image indicate what are normally taken to be the Montes Rook and Montes Cordillera ranges around Mare Orientale. There is some confusion regarding the IAU's definition of Montes Rook, which may include parts, or all, of the two rings indicated.


LPOD Photo Gallery Lunar Orbiter Images Apollo Images


(LAC zone 108B2) In USGS Digital Atlas mapped on LAC-90 PDF, LAC-73 PDF, LAC-108 PDF, and LAC-91 PDF. For an overview see Farside PDF. See also the older LMP-1 and LMP-2.


Cheek and others (2012) find the Inner Rook to be nearly pure anorthosite. Few such exposures occur elsewhere in the basin.


(IAU Directions) ROOK MOUNTAINS.--On the W. limb, extending from about S. lat. 18 deg. to S. lat. 35 deg. According to Schroter, they attain a height of 25,000 feet.


Montes Rook

Additional Information

  • The position and coordinates given in the title line differ from those in given on the IAU page.
  • The diameters of the "Rook" circles drawn above are 460 and 655 km, as measured on the Lunar Orbiter image. Spudis et al. (1984), give basin ring diameters of 500 and 620 km. Head (1974) gave 480 and 620 km. - JimMosher
  • Depth data from Kurt Fisher database
    • Viscardy, 1985: 6 km


  • Named for Lawrence Rook (1622-1666), a British astronomer.
  • The name was introduced by Johann Schröter, who used it to designate two peaks seen on the Moon's (in modern terminology) western limb in Plate LXIII of his book. With his typical meticulousness, Schröter explains on page 370 that the observation was made at 7 o'clock in the morning on August 27, 1788, four days before the New Moon, at which time the Moon was 32' 45" in diameter. The first peak could be located, he says, by extending a line from Gassendi through Zupus to the limb, along which line the distance from Zupus to the limb was 3' 40". The second peak, he says was seen 1' 20" south of the first. Unfortunately modern simulations based on altimeter-measured topography predict no obvious peaks on the limb at these locations on August 27, 1788, although all the other information provided sounds consistent with the observation having been made on that date (note, however, that the stated time implies an observation after sunrise). Possibly the spacecraft altimeters have thus far failed to sample them. - JimMosher
  • The name Rook Mts was part of the original 1935 IAU nomenclature of Blagg and Müller.
  • The understanding of the Rook Mts by early 20th century observers trying to follow the IAU nomenclature did not necessarily correspond to the present understanding of the term. For example, Wilkins and Moore place the Cordillera Mts well to the south, beyond Eichstadt on the far side of their Mare Orientale. They place the Rook Mts still farther south, beyond Vallis Bouvard and Inghirami, and at a similarly extreme longitude. These may correspond possibly to some of the more distant parts of what we would now call Montes Cordillera. The peaks on the nearside of Mare Orientale are not named. The Army Map Service's early LTM series (attempting to illustrate the Blagg and Müller nomenclature) placed these features in the a similar way, but not so far south (see LTM-2 and Shaded Topo 2). The Cordillera Mts are placed to the west of their Mare Veris (whereas on modern maps they are to the east), at the latitude of Crüger. The Rook Mts are on the extreme limb at the latitude of Eichstadt (where Wilkins and Moore placed the Cordilleras).
  • The name was deleted by Kuiper in Table III of his Photographic Lunar Atlas as being "limb mountains not readily indentifiable." His modification of Blagg and Müller was approved by the IAU in 1961.
  • At the recommendation of Arthur et al., the name was reinstated and Latinized to Montes Rook in 1964 (IAU Transactions XIIB). This was apparently as a result of the feature having been reidentified in preparing the Rectified Lunar Atlas. Since the name is not mentioned in any subsequent IAU Transactions, the identification (labeling) in the Rectified Lunar Atlas would appear to be the current IAU meaning of the term. Unfortunately, none of the-Moon Wiki editors seem to have access to that work.
  • Most lunar maps of this era, made after the availablity of space images such as that shown above, seem to have understood Montes Rook to be the outer of the two rings shown above (the 655-km diameter one), outside what is now called Lacus Veris and the crater Shuleykin, and with the craters Lallemand, Nicholson and Pettit on its crest. For example, on p. 129 of their The Moon as Viewed by Lunar Orbiter (1970) Kosofsky and El-Baz (who is believed to be the author of the lunar section of the original printed IAU Planetary Gazetteer), refer to "The Cordillera Mountain scarp, which is the outermost ring of the Orientale basin...and the Rook Mountains (the middle one of the basin's three rings)" [emphasis added]. See also, the labeling of the photographs and maps in NASA SP-241 (1971) and Rükl's Maps of lunar hemispheres 1972.
  • Although Kosofsky and El-Baz obviously recognized the 460-km ring, they did not think it was included in the IAU name Montes Rook. However, there is considerable evidence that the IAU intended to extend the original Earth-based name to include both the complete rings (all around the basin) and both the 460 and 655-km rings. Baum and Whitaker (p. 134) quote a May 8, 1969 memo written by then IAU Lunar Nomenclature Working Group chairman stating that "We recommend that ... Montes Rook be ... defined as a circle lying between Lacus Pacificus on the interior and Annulus Concordiae on the outer" (where Lacus Pacificus was a proposed name for the mare inside the 460-km ring and Annulus Concordiae was a proposed name for the region outside the 655-km ring, but inside the Cordillera ring). And a July 15, 1969 memo saying "We have agreed that ... we define Montes Rook as applying to the circular mountains bordering Mare Orientale. We recognize that this border is not entirely complete, but it is clearly part of the same basic system and therefore deserves the same name." However, none of this ever seems to have been brought up for a vote by the IAU General Assembly. So it does not seem that the definition in the Rectified Lunar Atlas (whatever that may be) has ever been superseded. Perhaps this explains the odd position and diameter quoted in the current IAU Planetary Gazetteer.
  • Beginning in about 1974, lunar geologists, feeling a need to have a name for the inner feature, began calling the 460-km ring the Inner Rook Ring (a non-IAU-defined term), distinguishing what had perhaps been the Earth-based Montes Rook as the Outer Rook Ring (Head, 1974). Discrepancies of this sort, between the terminology commonly used by geologists and that defined by the IAU, are not uncommon (see, for example, Apennine Front).
  • Later geologists have added still more rings, including the step at 320 km, which now makes the original(?) Montes Rook the "third" ring in the basin (Spudis et al., 1984). This innermost ring (or step) does not seem to have a name.
  • It should perhaps be noted that on most photos, the geologist's Outer Rook ring is clearest on the east side of the basin, and the Inner Rook ring is clearest in the west (largely in shadow in the example shown above).
  • In the new (but so far unofficial) USGS Digital Atlas, Montes Rook is identified partially with the 655-km ring and partially with the 480-km ring illustrated above. See, for example, the farside PDF and the details in LAC-90 and LAC-108. The southern and eastern sides of Montes Rook are identified with the 655-km ring, but the western and northern sides are identified with the 480 km ring. This interpretation seems to be based on NASA's LMP-1 and LMP-2, which also identifies the northern part of Montes Rook with the 480 km inner ring. Like the USGS Digital Atlas, this DMA-prepared LMP map series was intended to illustrate the IAU nomenclature, but it is not an official IAU document. Hence it is not known if the IAU name Montes Rook is intended to encompass both the 480 and 655 km rings, just the one illustrated here (the 655 km one), or portions of both.
  • The most recent description of the Orientale Basin nomenclature would seem to be that of Baum and Whitaker (2007), who say in the footnotes (p. 135):

  • The mare is defined by three concentric ring structures; the outer, the Montes Cordilleras ([sic]), has a diameter of 930km; the inner rings are the Outer and the Inner Montes Rook, which have diameters of 620 and 490km respectively.

  • (see the Montes Cordillera page): If the offical IAU nomenclature has Rook Mountains as the 655 ring only, then the IAU is about 40 years behind science in recognizing that there are two Rook rings. The best understanding of the nature and position of the Inner and Outer Rook Mountains comes from the geologists (USGS, Univ of AZ and Brown Univ) who studied and mapped them in detail. - tychocrater Oct 30, 2007
  • I think the best way to understand this is that both rings constitute the Rooks Mountains, which are subdivided by geologists into an Inner Rook ring and an Outer Rook ring. There is no reason for the Inner and Outer names to be official IAU name. There is no issue here to be resolved. - tychocrater
  • Called "Montes ROCK" on Rand McNally's greenish colored Moon map (a typographical error!). - DannyCaes May 3, 2008

LPOD Articles

(see Mare Orientale for a collection of LPOD articles depicting and discussing Montes Rook and the Inner and Outer Rook Rings)
An Overlooked Gem


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