Secondary crater

from Wikipedia, the free encyclopedia

A secondary crater is a crater in the astronomical nomenclature of the moon , the name of which consists of the name of a nearby, usually larger and more prominent crater and an appended Latin capital letter, for example Ptolemaeus B located near the crater Ptolemaeus . The larger crater is also the main crater (English parent feature called).

Moon crater Aristarchus and the surrounding area with its nine secondary craters


The form of designation was introduced by Wilhelm Beer and Johann Heinrich Mädler in their Mappa selenographica in order to name smaller, previously unnamed surface structures, whereby only the letter appeared on the card for reasons of space. The assignment resulted from the fact that the letter was positioned on the edge of the crater closest to the main crater , a system that later gave rise to some inaccuracy and confusion.

This ambiguity was clarified by Blagg et al. Cleared out in 1935, which, on behalf of Commission 16 of the International Astronomical Union (IAU), harmonized and standardized the nomenclature that had existed up to that point and named numerous other craters with letters, in which case double letters were also used. In addition, surveys were named using Greek letters. This process was continued in the System of Lunar Craters of the Lunar and Planetary Laboratory at the University of Arizona , with all craters on the earth-facing side over 3.5 km in diameter named.

In 1973 the IAU decided that names with letters should be gradually replaced by names after deceased persons in the future. This renaming process made very slow progress and the work of the then Task Group for Lunar Nomenclature (TGLN) was widely criticized by selenographers for the inconsistencies and ambiguities it created. Nevertheless, until 2006 only renamed craters with the additional indication of the letter were cited in the official IAU sources. Since then, the approximately 7,000 secondary crater names have also been considered official and appear in the IAU's Gazetteer of Planetary Nomenclature , for example .

Since the official nomenclature of the moon did not make adequate progress after 1973, the work was continued by NASA , especially since numerous craters of scientific interest on the back of the moon had not yet been named. In this effort, interested groups and people outside NASA were also included in the Lunar Photography and Cartography Committee (LPACC). The work led to the 1982 published NASA-RPC-1097 by Andersson and Whitaker. In it, secondary crater names were given for numerous craters on the back of the moon, using the following system: The main crater is the center of a 24-hour clock with 12 o'clock in the north, where the hours correspond to the Latin letters with the exception of I and O. Secondary craters are then named according to the hour field in which they are located. In addition, all designations with double letters have been dropped. In the IAU nomenclature, however, some designations with double letters have been retained.

special cases

For historical reasons, in some rare cases the main structures are not impact craters , but other structures, mainly mountains or mountain ranges:

At the Gerard crater there are the nested secondary craters Gerard Q Inner and Gerard Q Outer .


  • Ewen A. Whitaker: Mapping and naming the moon. A History of Lunar Cartography and Nomenclature. Cambridge University Press, Cambridge et al. 1999, ISBN 0-521-62248-4 , pp. 171 ff.
  • Leif E. Andersson , Ewen A. Whitaker: NASA catalog of lunar nomenclature (= NASA reference publication. 1097). National Aeronautics and Space Administration - Scientific and Technical Information Branch, Washington DC 1982.
  • Mary Adela Blagg , Karl Müller : Named lunar formations. 2 volumes (volume 1: catalog; volume 2: maps). P. Lund - Humphries & Co, London 1935.

Web links

Individual evidence

  1. ^ Wilhelm Beer, Johann Heinrich Mädler: Mappa selenographica totam Lunae hemisphaeram visibilem complectens observationibus propriis secundum projectionem orthographicam quartuor sectionibus constructa et delineata. Schropp, Berlin 1834.
  2. ^ Wilhelm Beer, Johann Heinrich Mädler: The moon according to its cosmic and individual circumstances or general comparative selenography. With special reference to the Mappa Selenographica edited by the authors. Schropp, Berlin 1837.
  3. ^ DWG Arthur, Alice P. Agnieray, Ruth A. Horvath, CA Wood, CR Chapman: The System of Lunar Craters, Quadrant I. In: Communications of the Lunar and Planetary Laboratory. Vol. 2, No. 30, 1963, ZDB -ID 1025348-8 , pp. 71-78, digital version (PDF; 9.32 MB) .
  4. ^ "Craters previously designated by Roman capital letters will progressively be assigned new and distinctive names." Resolution on Lunar Nomenclature, point 5 in: George Contopoulos, Arnost Jappel (ed.): International Astronomical Union. Proceedings of the Fifteenth General Assembly, Sydney 1973 and extraordinary General Assembly, Poland 1973 (= Transactions of the International Astronomical Union. Vol. 15 B). Reidel, Dordrecht 1974, ISBN 90-277-0451-1 , pp. 110-112, online .
  5. Whitaker: mapping and naming the moon. 1999, pp. 179-184.
  6. Whitaker: mapping and naming the moon. 1999, p. 184 f.
  7. In this respect, the more neutral English term satellite feature is more appropriate.