Hell Q

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Hell Q

(IAU crater name. The informal name for the patch of bright ejecta seen in this area at Full Moon is Cassini's Bright Spot. The IAU name Hell Q originally referred to this bright patch, rather than to a crater, and the present crater was probably known at that time as Hell H)

Lat: 33.0°S, Long: 4.4°W, Diam: 4 km, Depth: 1 km, Rükl: 65

external image normal_Hell_Q_LO-IV-112H_LTVT.JPG
LO-IV-112H The crater presently known as Hell Q (see Nomenclature) is at the center of this view depicting a relatively small area on the floor of Deslandres. The Lunar Orbiter image has been remapped to a zero-libration (Earth-based) view, which accounts for the elliptical shape of the craters. To the northeast of Hell Q is a small sunlit peak, and beyond that the weathered 8-km diameter crater Walther G. The area between these becomes quite bright around Full Moon, creating a feature that is informally known as Cassini's Bright Spot. An identically scaled Clementine image, taken with a higher Sun angle, shows the area of the bright ejecta more clearly. The effect becomes even more striking when the area is viewed along the direction of the sunlight (for example from Earth at Full Moon). Under those circumstances, the ejecta become brighter still, and the surrounding shadowed topography fades, leaving a bright spot seen against a bland background.


LPOD Photo Gallery Lunar Orbiter Images

  • For wider-angle examples of the appearance of the Hell Q region as seen near Full Moon see the detail from the Full Moon image by Mario Weigand taken at a phase angle of 5.3 degrees, and the same areas as seen in a Yerkes Observatory plate taken at a phase angle of 1.52 degrees. These images span the region from Pitatus in the upper left to Tycho at the bottom. The crater Hell (after which Hell Q is named) is the bright-haloed dark spot to the left of, and slightly above, the bright spot, along the centerline; especially visible in Mario's image. In that image, Hell Q is the relatively dark circle at the lower left edge of the most intense part of the bright patch. The wider extent of the bright area in the Yerkes plate, and its more diffuse appearance, may be mostly a difference in the processing of the photo.
  • The Lunar Reconnaissance Orbiter's (LRO's) extreme close up of crater Hell Q is detectable at LON: -4.45, LAT: -32.99 on the ACT-REACT Quick Map.- DannyCaes Jun 19, 2011


(LAC zone 112A2) LAC map Geologic map


Hell Q is a rather ordinary crater. The main reason for there being any interest in it is that it is fresh, and seems to be the source of a patch of bright ejecta that dust the surrounding area, especially (the result of an oblique impact?) some gentle slopes to its northeast. The patch becomes particularly bright and extensive looking around the time of Full Moon. The early telescopic observer Giovanni Cassini is thought to have mistaken it for a temporary white cloud, hence the informal name.

Description: Elger

(IAU Directions) in his List Of The Principal Ray-Systems, Light-Surrounded Craters, And Light-Spots: Hell. A large ill-defined spot in W. long. 4 deg., S. lat. 33 deg. This is most probably the site of the white cloud seen by Cassini.

Description: Wikipedia


Additional Information

  • Hell Q is placed at 33.01°S / 4.55°W in the new Warped Clementine Basemap, which is supposed to place features at their correct positions according to the ULCN 2005.
  • From the shadows in LO-IV-107H and LO-IV-112H Hell Q appears to be about 1000 m deep (the shadows don't reach fully to the bottom). The smaller crater to its east (the Hell Q of the System of Lunar Craters) appears to be much shallower, probably not much more than about 300 m deep. - JimMosher


  • Hell Q is named after the nearby crater (Hell).
  • The nomenclature history of this region is very confused. Mary Blagg, in her Collated List of 1913 found a crater labeled Hell d by all three of her authorities (Mädler, Schmidt and Neison) in the vicinity of the present Hell Q. Instead of renaming this Hell D Blagg and Müller (1935) chose the name Hell H (a name Neison had used for a "fine wide valley" that he placed slightly to the east of Hell d and described as extending "from Lexell towards Hell Gamma." Still further to the east, Neison (p. 372) assigned the name Hell Q to the "great bright spot seen at low illumination to be a level plain surrounded by low hills and valleys." Since none of Blagg's other authorities assigned a name to the bright patch, the name Hell Q as used in Blagg and Müller presumably refers to Neison's patch, probably corresponding most nearly to the bright peak in the image at the top of this page. Although apparently not named by Mädler, the bright patch must have been described in his book, for Neison recounts the story (from Mädler), that "near here appeared the celebrated white cloud of Cassini, which soon after disappeared, and in its place he saw a new formation," most likely one of the neighboring craters. Neison (or is it Mädler?) speculates that when Cassini viewed the same area at a lower sun angle he most likely saw Hell or Hell B at the position where he remembered seeing the white cloud.
  • In the System of Lunar Craters, and on LAC 112, the name Hell H was moved to a different crater that was probably unnamed in Blagg and Müller. At the same time, names were assigned to three of the craters to the west of the bright patch (the former Hell Q), with the name Hell Q being re-assigned to the 3.4 km crater below the bright peak (to the right of center in the image at the top of this page). The more prominent 4-km crater in the center (which actually appears to be the source of the bright patch) was labeled Hell QA and the slightly smaller crater at 7 o'clock from that was labeled Hell QB. Also, the prominent crater along the upper centerline (to the left of the newly named Hell H) was given the name Hell HA.
  • NASA SP-241, which contains a long series of annotated Lunar Orbiter images, but is not an IAU-approved publication, identifies Hell Q in two different ways. On page 173 (based on LO-IV-107-H3) follows the lettering of LAC 112 (that is, Hell Q is identified as the relatively inconspicuous crater below the bright peak, and the more prominent one to its left is unlabeled). On page 183 (based on LO-IV-112-H3) Hell Q is identified as the more prominent of these two craters, and the less inconspicuous crater below the bright peak is unlabeled. In both versions, Hell QA (upper, at 8 o'clock) and QB (lower, at 7 o'clock) are identified as the two craters to the west of the most prominent one. This agrees with the System of Lunar Craters and LAC 112 with regard to the lower crater, but differs as to the upper one (the upper crater on the west is unlabeled in these earlier works, and Hell QA is used instead for the more prominent crater).
  • In NASA RP-1097 (which since 2006 has been the basis of the lettered craters in the official on-line IAU Planetary Gazetteer), the names Hell QA, QB and HA were all dropped, and the coordinates given for Hell Q are those of the crater formerly known in the System of Lunar Craters as Hell QA.
  • In summary, Hell Q seems to have had three distinct meanings in the IAU Nomenclature. From 1935 to ~1963 it was an albedo feature corresponding to the entire bright patch as described by Neison (per Blagg and Müller). From ~1963 to 2006 it meant instead the small crater immediately to the south of the small bright peak (per the System of Lunar Craters and LAC 112). Since 2006 (per the replacement of the lettered crater list in the System of Lunar Craters with that in NASA RP-1097) it has meant the more prominent crater to the southwest of the small bright peak. The present crater seems also to have had three distinct designations: first Hell H (a name now used for a completely unrelated crater), then Hell QA, and finally Hell Q.
  • In his 1999 book, Ewen Whitaker notes (p. 208) that the "very bright nimbus at Deslandres QA" was labeled Mons Tabor by Hevelius. Since there is no Deslandres QA (?) this is presumably a reference to one of the variants of Hell QA.
  • In the current IAU nomenclature, in addition to Hell Q and Walther G, the image shown at the top of this page includes three other IAU-named craters: 4-km Hell P (a little above the center of the left edge), 5-km Hell K (the largest of the three craters in the lower left), and 5-km Hell H (along the top edge, on the right -- the crater with the strongly raised east rim).

LPOD Articles

Cassini and Q

LROC Articles

Anaglyph of Hell Q crater