Gertrude Is Largest Known Crater on Largest Uranian Moon Titania

Summary: Gertrude is the largest known crater on largest Uranian moon Titania, which was discovered by Uranus discoverer William Herschel on Jan. 11, 1787.

Gertrude (center left, between 270 and 300 degrees east), the largest known crater on largest Uranian moon Titania, lies in the Titania’s Uranus-facing southern hemisphere; U.S. Geological Survey, The Southern Hemispheres of Umbriel, Titania, and Oberon; prepared for the Voyager Imaging Science Team in Cooperation With the Jet Propulsion Laboratory, California Institute of Technology and The National Aeronautics and Space Administration, 1988; mosaic made with Voyager 2 images 1523U2-001 and 1137U2-001: U.S. Geological Survey, via IAU Gazetteer of Planetary Nomenclature

Gertrude is the largest known crater on largest Uranian moon Titania, which was discovered by German-British astronomer William Herschel (Nov. 15, 1738-Aug. 25, 1822) on Jan. 11, 1787, five years nine months 29 days after his discovery of Titania’s primary body, Uranus.

Gertrude is centered at minus 15.8 degrees south latitude and 287.1 degrees east longitude, according to the International Astronomical Union’s Gazetteer of Planetary Nomenclature. Gertrude’s northernmost and southernmost latitudes extend to minus 14.1 degrees south and minus 17.6 degrees south, respectively. The impact crater’s easternmost and westernmost longitudes reach 297.1 degrees east and 277.1 degrees east, respectively. Gertrude’s diameter spans 326 kilometers.

Gertrude’s diameter approximates one-fifth of Titania’s diameter. As the largest Uranian satellite, Titania has an approximate diameter of 1,578 kilometers, according to planetary geologist Jeffrey M. Moore and his four planetary scientist co-authors, Paul M. Schenk, Lindsey S. Bruesch, Erik Asphaug and William B. McKinnon, in their article, “Large Impact Features on Middle-Sized Icy Satellites,” in the October 2004 issue of Icarus. Titania’s radius is calculated at 788.9 kilometers, according to “Uranian Satellite Fact Sheet” by Goddard Space Flight Center (GSFC) planetary scientist David Richard Williams on the NASA Space Science Data Coordinated Archive (NSSDCA) website.

Moore and his four co-authors describe Gertrude as a “raised rim, circular feature” (page 436). The authors’ colorized digital elevation models (DEMs) of map-projected Voyager 2 image (Flight Data Subsystem FDS 26843.13) reveal Gertrude’s typical impact rim, which rises approximately 2 kilometers above the crater’s floor. In their July 4, 1986, article in Science, astronomer Bradford A. Smith and 39 co-authors (including astrophysicist and cosmologist Carl Sagan and astrogeology pioneer Eugene Shoemaker) proposed the formation of Titania’s few large impacts from bombardment by impactors or orbital debris or both.

An annular (ring-shaped) dome is centrally located on the crater’s floor. The dome has a diameter of approximately 150 kilometers and reaches an elevation of 2 to 3 kilometers. The authors note that the dome is superimposed by only a few craters.

The compatible elevations of Gertrude’s rim and central dome are also comparable with the elevations of the crater’s environs. Moore’s team finds that Gertrude’s low topographic relief and paucity of impact ejecta-created landforms suggest the crater’s post-impact modification, for example, through coverage by emplaced materials.

Gertrude lies in Titania’s Uranus-facing southern hemisphere. Two smaller craters, Lucetta and Mopsa flank Gertrude.

Lying to Gertrude’s west, Lucetta is centered at minus 14.7 degrees south latitude, 277.1 degrees east longitude. The small crater obtains northernmost and southernmost latitudes at minus 14.4 degrees south and minus 15 degrees south, respectively. It marks its easternmost and westernmost longitudes at 279.6 degrees east and 274.6 degrees east, respectively. Lucetta’s diameter measures 58 kilometers.

Lying to Gertrude’s east, Mopsa is centered at minus 11.9 degrees south latitude, 302.2 degrees east longitude. Mopsa registers northernmost and southernmost latitudes at minus 11.4 degrees south and minus 12.4 degrees south, respectively. Its easternmost and westernmost longitudes occur at 305.9 degrees east and 298.5 degress east, respectively. Mopsa has a diameter of 101 kilometers.

Characters in plays by Elizabeth playwright William Shakespeare (bapt. April 26, 1564-April 23, 1616) inspired the names of Titanian craters Gertrude, Lucetta and Mopsa. Gertrude recalls the protagonist’s mother in “The Tragedy of Hamlet, Prince of Denmark.” Lucetta’s namesake is a waiting woman in “Two Gentlemen of Verona.” Mopsa is named after a shepherdess in “The Winter’s Tale.” The IAU approved the craters’ name in 1988, during the organization’s XXth (20) General Assembly, held Tuesday, Aug. 2, to Thursday, Aug. 11, in Baltimore, Maryland.

The takeaways for Gertrude as the largest known crater on largest Uranian moon Titania are that Gertrude's diameter of 326 kilometers equates to approximately one-fifth of Titania's diameter and that the large Titanian impact crater's namesake is the protagonist's mother in Elizabethan playwright William Shakespeare's The Tragedy of Hamlet, Prince of Denmark.

Uranus’ south pole (bright area on left) in NASA Hubble Space Telescope image obtained in 2006; NASA’s Voyager 2 spacecraft’s images of Uranus, its rings and its satellites, obtained during January 1986 flyby, covered only the Uranian system’s southern hemisphere because of the current closeness of the planet and satellites’ subsolar points to their south poles; NASA, ESA (European Space Agency, L. Sromovsky and P. Fry (University of Wisconsin), H. Hammel (Space Science Institute) and K. Rages (SETI Institute): NASA Hubble Space Telescope (NASA Hubble), CC BY 2.0 Generic, via Flickr

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Gertrude (center left, between 270 and 300 degrees east), the largest known crater on largest Uranian moon Titania, lies in the Titania’s Uranus-facing southern hemisphere; U.S. Geological Survey, “Pictorial Map of Titania Ut 10M -90/0 AN,” The Southern Hemispheres of Umbriel, Titania, and Oberon; prepared for the Voyager Imaging Science Team in Cooperation With the Jet Propulsion Laboratory, California Institute of Technology and The National Aeronautics and Space Administration, 1988; mosaic made with Voyager 2 images 1523U2-001 and 1137U2-001: U.S. Geological Survey, via IAU Gazetteer of Planetary Nomenclature @ https://planetarynames.wr.usgs.gov/images/umbriel_titania_oberon_I-1920_300dpi.pdf

Uranus’ south pole (bright area on left) in NASA Hubble Space Telescope image obtained in 2006; NASA’s Voyager 2 spacecraft’s images of Uranus, its rings and its satellites, obtained during January 1986 flyby, covered only the Uranian system’s southern hemisphere because of the current closeness of the planet and satellites’ subsolar points to their south poles; NASA, ESA (European Space Agency, L. Sromovsky and P. Fry (University of Wisconsin), H. Hammel (Space Science Institute) and K. Rages (SETI Institute): NASA Hubble Space Telescope (NASA Hubble), CC BY 2.0 Generic, via Flickr @ https://www.flickr.com/photos/nasahubble/46455057294/;
Public Domain, via Windows to the Universe @ https://www.windows2universe.org/uranus/uranus_polar_regions.html

For further information:

Buratti, Bonnie J.; and Joel A. Mosher. “Comparative Global Albedo and Color Maps of the Uranian Satellites.” Icarus, vol. 90, no. 1 (March 1991): 1-13.
Available via ScienceDirect @ https://www.sciencedirect.com/science/article/abs/pii/001910359190064Z?via%3Dihub

Davies, Merton E.; Tim R. Colvin; Frank Y. Katayama; and Peter C. Thomas. “The Control Networks of the Satellites of Uranus.” Icarus, vol. 71, issue 1 (July 1987): 137-147.
Available via ScienceDirect @ https://www.sciencedirect.com/science/article/abs/pii/0019103587901680

International Astronomical Union (IAU) / U.S. Geological Survey (USGS) Gazetteer of Planetary Nomenclature. “Gertrude.” USGS Astrogeology Science Center > Gazetteer of Planetary Nomenclature > Nomenclature > Uranus.
Available @ https://planetarynames.wr.usgs.gov/Feature/2150

International Astronomical Union (IAU) / U.S. Geological Survey (USGS) Gazetteer of Planetary Nomenclature. “Lucetta.” USGS Astrogeology Science Center > Gazetteer of Planetary Nomenclature > Nomenclature > Uranus.
Available @ https://planetarynames.wr.usgs.gov/Feature/3501

International Astronomical Union (IAU) / U.S. Geological Survey (USGS) Gazetteer of Planetary Nomenclature. “Mopsa.” USGS Astrogeology Science Center > Gazetteer of Planetary Nomenclature > Nomenclature > Uranus.
Available @ https://planetarynames.wr.usgs.gov/Feature/4028

International Astronomical Union (IAU) / U.S. Geological Survey (USGS) Gazetteer of Planetary Nomenclature. “Target: Titania.” USGS Astrogeology Science Center > Gazetteer of Planetary Nomenclature > Nomenclature > Uranus.
Available @ https://planetarynames.wr.usgs.gov/Page/TITANIA/target

Johnson, Torrence V.; Robert H. Brown; and James B. Pollack. “Uranus Satellites: Densities and Composition.” JGR (Journal of Geophysical Research) Space Physics, vol. 92, issue A13 (Dec. 30, 1987): 14884-14894.
Available via Wiley Online @ https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JA092iA13p14884

Johnson, Torrence V.; Robert Hamilton Brown; and Laurence A. Soderblom. “The Moons of Uranus.” Scientific American, vol. 256, no. 4 (April 1987): 48-61.
Available via JSTOR @ https://www.jstor.org/stable/24979362

Lavoie, Sue; Lisa Gaddis; and Rafael Alanis, webmaster. “c2684313.ibg.” NASA Jet Propulsion Laboratory PDS Imaging Node > Data.
Available @ https://pds-imaging.jpl.nasa.gov/data/vg2-u-iss-2-edr-v1.0/vg_0003/browse/titania/c2684313.ibg

Levy, David H. Skywatching. Revised and updated. San Francisco CA: Fog City Press, 1994.

Marriner, Derdriu. “William Herschel Discovered First Two Uranian Moons on Jan. 11, 1787.” Earth and Space News. Wednesday, Jan. 12, 2011.
Available @ https://earth-and-space-news.blogspot.com/2011/01/william-herschel-discovered-first-two.html

McNally, D. (Derek), ed. XXth General Assembly Transactions of the IAU Vol. XX B Proceedings of the 20th General Assembly Baltimore, MD, August 2-11, 1988. Alphen aan den Rijn, Netherlands: Kluwer Academic Publishers, Jan. 1, 1990.
Available @ https://www.iau.org/publications/iau/transactions_b/

Moore, Jeffrey M.; Paul M. Schenk; Lindsey S. Bruesch; Erick Asphaug; and William B. McKinnon. “Large Impact Features on Middle-Sized Icy Satellites.” Icarus, vol. 171, no. 2 (October 2004): 421-443.
Available @ http://planets.oma.be/ISY/pdf/article_Icy.pdf

Moore, Patrick, Sir. Philip’s Atlas of the Universe. Revised edition. London UK: Philip’s, 2005.

Nelson, Jon; and Anil Natha and Luis Espinoza, webmasters. “Uranus Approach.” NASA JPL Caltech Voyager > Mission > Science > Uranus.
Available @ https://voyager.jpl.nasa.gov/mission/science/uranus/

Nemiroff, Robert; and Jerry Bonnell. “Titania’s Trenches.” NASA (National Aeronautics and Space Administration) APOD (Astronomy Picture of the Day). Jan. 11, 1997.
Available @ https://apod.nasa.gov/apod/ap970111.html

Nemiroff, Robert; and Jerry Bonnell. “Uranus’ Largest Moon: Titania.” NASA (National Aeronautics and Space Administration) APOD (Astronomy Picture of the Day). March 4, 1996.
Available @ https://apod.nasa.gov/apod/ap960304.html

Plescia, J.B. “Cratering History of the Uranian Satellites: Umbriel, Titania and Oberon.” Journal of Geophysical Research, vol. 92, issue A13 (Dec. 30, 1987): 14918-14932.
Available via Wiley Online @ https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JA092iA13p14918

Russell, Randy. “The Poles of Uranus.” Windows to the Universe > Solar System > Planets > Uranus. Last modified May 5, 2009.
Available @ https://www.windows2universe.org/uranus/uranus_polar_regions.html

Shehktman, Lonnie; and Jay Thompson. “Titania: In Depth.” NASA Science Solar System Exploration > Moons > Uranus.
Available @ https://solarsystem.nasa.gov/moons/uranus-moons/titania/in-depth/

Shehktman, Lonnie; and Jay Thompson. “Titania: By the Numbers.” NASA Science Solar System Exploration > Moons > Uranus.
Available @ https://solarsystem.nasa.gov/moons/uranus-moons/titania/by-the-numbers/

Smith, B.A.; L.A. Soderblom; R. Beebe; D. Bliss; J.M. Boyce; A. Brahic; G.A. Briggs; R.H. Brown; S.A. Collins; A.F. Cook; S.K. Croft; J.N. Cuzzi; G.E. Danielson; M.E. Davies; T.E. Dowling; D. Godfrey; C.J. Hansen; C. Harris; G.E. Hunt; A.P. Ingersoll; T.V. Johnson; R.J. Krauss; H. Masursky; D. Morrison; T. Owen; J.B. Plescia; J.B. Pollack; C.C. Porco; K. Rages; C. Sagan; E.M. Shoemaker; L.A. Sromovsky; C. Stoker; R.G. Strom; V.E. Suomi; S.P. Synnott; R.J. Terrile; P. Thomas; W.R. Thompson; and J. Veverka. “Voyager 2 in the Uranian System: Imaging Science Results.” Science, new series, vol. 233, no. 4759 (July 4, 1986): 43-64.
Available via JSTOR @ https://www.jstor.org/stable/1697495
Available via Zenodo @ https://zenodo.org/record/1230972#.XcxDzFdKiUk

U.S. Geological Survey. “Pictorial Map of Titania Ut 10M -90/0 AN.” The Southern Hemispheres of Umbriel, Titania, and Oberon. Prepared for the Voyager Imaging Science Team in Cooperation With the Jet Propulsion Laboratory, California Institute of Technology and The National Aeronautics and Space Administration. Reston VA: U.S. Department of the Interior, 1988.
Available @ https://planetarynames.wr.usgs.gov/images/umbriel_titania_oberon_I-1920_300dpi.pdf

U.S. Geological Survey. Plate 3. “Pictorial Map of Titania Ut 10M -90/0 AN.” The Southern Hemispheres of Umbriel, Titania, and Oberon. Prepared for the Voyager Imaging Science Team in Cooperation With the Jet Propulsion Laboratory, California Institute of Technology and The National Aeronautics and Space Administration. Reston VA: U.S. Department of the Interior, 1988.
Available @ https://pubs.usgs.gov/imap/1920/plate-3.pdf

U.S. Geological Survey. The Southern Hemispheres of Umbriel, Titania, and Oberon. Prepared for the Voyager Imaging Science Team in Cooperation With the Jet Propulsion Laboratory, California Institute of Technology and The National Aeronautics and Space Administration. Reston VA: U.S. Department of the Interior, 1988.
Available @ https://planetarynames.wr.usgs.gov/images/umbriel_titania_oberon_I-1920_300dpi.pdf

Williams, David R. (Richard), Dr. “Uranus Fact Sheet.” NASA GSFC (Goddard Space Flight Center) NSSDC (NASA Space Science Data Coordinated Archive) > Solar System Exploration > Planetary Science > Uranus.
Available @ https://nssdc.gsfc.nasa.gov/planetary/factsheet/uranusfact.html

Williams David R. (Richard), Dr. “Uranian Satellite Fact Sheet.” NASA GSFC (Goddard Space Flight Center) NSSDC (NASA Space Science Data Coordinated Archive) > Solar System Exploration > Planetary Science > Uranus.
Available @ https://nssdc.gsfc.nasa.gov/planetary/factsheet/uraniansatfact.html