Near Side Julius Caesar Crater Honors Roman General and Statesman

Summary: Near side Julius Caesar Crater honors Roman general and statesman Gaius Julius Caesar, whose accomplishments included introducing the Julian calendar.

Julius Caesar Crater (left center) neighbors west of Mare Tranquillitatis and south-southwest of Mare Serenitatis on lunar near side's northeastern quadrant; Moon 1:10 million-scale Shaded Relief and Color-coded Topography, Near Side High Resolution: via USGS Astrogeology Science Center / Gazetteer of Planetary Nomenclature

Lunar near side Julius Caesar Crater honors Roman general and statesman Gaius Julius Caesar, whose achievements included the establishment of the Julian calendar.

Julius Caesar Crater occupies the lunar near side's northeastern quadrant. The low northern latitude impact crater resides near the moon's prime meridian, which marks zero degrees longitude on the lunar disc.

Julius Caesar Crater is centered at 9.17 degrees north latitude, 15.21 degrees east longitude, according to the International Astronomical Union’s (IAU) Gazetteer of Planetary Nomenclature. The northern hemisphere crater records northernmost and southernmost latitudes of 10.56 degrees north and 7.77 degrees north, respectively. The eastern hemisphere crater registers easternmost and westernmost longitudes of 16.63 degrees east and 13.80 degrees east, respectively. Julius Caesar Crater has a diameter of 84.72 kilometers.

Caesar's impact crater lies near the northwestern edges of Mare Tranquillitatis ("Sea of Tranquility"). Its location places it south-southwest of Mare Serenitatis ("Sea of Serenity") and southwest of Sinus Honoris ("Bay of Honor"), the Sea of Tranquility's northern and northwestern neighbors.

Mare Tranquillitatis is centered at 8.35 degrees north latitude, 30.83 degrees east longitude. Northernmost and southernmost latitudes for the lunar mare (Latin: mare, "sea"; plural, maria, "seas") touch 19.37 degrees north and minus 4.05 degrees south, respectively. The dark, basaltic plain's easternmost and westernmost longitudes tap 45.49 degrees east and 16.92 degrees east, respectively. Mare Tranquillitatis has a diameter of 875.75 kilometers.

Mare Serenitatis is centered at 27.29 degrees north latitude, 18.36 degrees east longitude. Northernmost and southernmost latitudes for the lunar mare reach 37.81 degrees north and 16.13 degrees north, respectively. The dark plain's easternmost and westernmost longitudes extend to 29.92 degrees east and 6.59 degrees east, respectively. Mare Serenitatis has a diameter of 674.28 kilometers.

Sinus Honoris is centered at 11.72 degrees north latitude, 17.87 degrees east longitude. The small northern hemisphere-sited plain (Latin: sinus, "bay") finds its northernmost and southernmost latitudes at 13.26 degrees north and 9.92 degrees north, respectively. The eastern hemisphere bay obtains its easternmost and westernmost longitudes at 19.26 degrees east and 15.49 degrees east, respectively. Sinus Honoris has a diameter of 111.61 kilometers.

Julius Caesar Crater is situated to the west-northwest of Sosigenes Crater's location on the western edge of Mare Tranquillitatis. Sosigenes Crater is centered at 8.70 degrees east latitude, 17.60 degrees east longitude. The northern hemisphere-dwelling circular impact crater realizes northernmost and southernmost latitudes at 8.98 degrees north and 8.42 degrees north, respectively. The eastern hemisphere-sited bright crater recognizes its easternmost and westernmost longitudes at 17.88 degrees east and 17.31 degrees east, respectively. Sosigenes Crater's diameter measures 16.99 kilometers.

"A large incomplete formation of irregular shape," assessed British selenographer Thomas Gwyn Empy Elger (Oct. 27, 1836-Jan. 9, 1897) in his description of Julius Caesar Crater in his Victorian era lunar guide, The Moon: A Full Description and Map of Its Principal Physical Features, published in 1895. "The floor of Julius Caesar is uneven in tone, becoming gradually duskier from S. to N., the northern end ranking among the darkest areas on the lunar surface" (page 56).

In his lunar descriptions, Elger followed the convention of correlating east and west on the moon with the observer's eastern and western horizons. Consequently, he referenced Julius Caesar Crater's heavily worn western wall as eastern. "The wall on the E. is much terraced and forms a flat 'S' curve."

The International Astronomical Union officially approved Julius Caesar Crater’s name in 1935, during the organization’s Vth (5th) General Assembly, held Wednesday, July 10, to Wednesday, July 17, in Paris, France. Lunar Crater Julius Caesar honors first century BCE Roman general and statesman Gaius Julius Caesar (July 12, 100 BCE-March 15, 44 BCE).

Julius Caesar's achievements expand beyond military campaigns and statesmanship to include an astronomical contribution. In 46 BCE, during his third of five consulships, Caesar considered the dissatisfactory irregularities in the lunar-based Roman calendar, according to Greek biographer Plutarch (46 BCE-ca. 122 CE) in Lives of the Noble Greeks and Romans, commonly known as Parallel Lives.

"The adjustment of the calendar, however, and the correction of the irregularity in the computation of time, were not only studied scientifically by him, but also brought to completion, and proved to be of the highest utility. For not only in very ancient times was the relation of the lunar to the solar year in great confusion among the Romans, so that the sacrificial feasts and festivals, diverging gradually, at last fell in opposite seasons of the year, but also at this time people generally had no way of computing the actual solar year; the priests alone knew the proper time, and would suddenly and to everybody's surprise insert the intercalary month called Mercedonius. . . . But Caesar laid the problem before the best philosophers and mathematicians, and out of the methods of correction which were already at hand compounded one of his own which was more accurate than any," according to the translation (volume VII, page 579, 581) first published in 1919 by American classicist Bernadotte Perrin (Sep. 15, 1847-Aug. 31, 1920).

Caesar's new solar-based calendar took effect Jan. 1, 45 BCE, during his fourth consulship. The Julian calendar's first year lasted a lengthy 445 days. Its lengthiness reconciled Roman Calendar problems, such as seasonal drift-occasioned discrepancy between the calendar and the tropical year of the full annual solar cycle. Beginning in 44 BCE, during Caesar's fifth consulship, his calendar observed 365 days, with the addition of an extra day every fourth year.

image of Julius Caesar Crater, spliced 2013 by Wikimedia user James Stuby (Jstuby at English Wikipedia) from Frames 4090 h1 and h2 obtained during NASA's Lunar Orbiter IV mission, which acquired photographic data (419 high resolution and 127 medium resolution frames) from May 11 to 26, 1967: James Stuby at English Wikipedia, CC0 1.0 Universal (CC0 1.0) Public Domain Dedication, via Wikimedia Commons

Acknowledgment

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

Image credits:

Julius Caesar Crater (left center) neighbors west of Mare Tranquillitatis and south-southwest of Mare Serenitatis on lunar near side's northeastern quadrant; Moon 1:10 million-scale Shaded Relief and Color-coded Topography, Near Side High Resolution: via USGS Astrogeology Science Center / Gazetteer of Planetary Nomenclature @ https://asc-planetarynames-data.s3.us-west-2.amazonaws.com/moon_nearside.pdf

image of Julius Caesar Crater, spliced 2013 by Wikimedia user James Stuby (Jstuby at English Wikipedia) from Frames 4090 h1 and h2 obtained during NASA's Lunar Orbiter IV mission, which acquired photographic data (419 high resolution and 127 medium resolution frames) from May 11 to 26, 1967: James Stuby at English Wikipedia, CC0 1.0 Universal (CC0 1.0) Public Domain Dedication, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Julius_Caesar_crater_4090_h1_4090_h2.jpg; via USRA LPI (Lunar and Planetary Institute) @ https://www.lpi.usra.edu/resources/lunarorbiter/frame/?4090

For further information:

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Elger, Thomas Gwyn. “JULIUS CAESAR.--A large incomplete formation of irregular shape. The wall on the E. is much terraced, and forms a flat 'S' curve. The summit ridge is especially bright, and has a conspicuous little crater upon it. On the W. is a number of narrow longitudinal valleys trending from N. to S., included by a wide valley which constitutes the boundary on this side. The border on the S. consists of a number of low rounded banks, those immediately E. of Sosigenes being traversed by several shallow valleys, which look as if they had been shaped by alluvial action. There is a brilliant little hill at the end of one of these valleys, a few miles E. of Sosigenes. The floor of Julius Caesar is uneven in tone, becoming gradually duskier from S. to N., the northern end ranking among the darkest areas on the lunar surface. There are at least three large circular swellings in the interior. A long low mound, with two or three depressions upon it, bounds the wide valley on the E. side.” Page 56. The Moon: A Full Description and Map of Its Principal Physical Features: First Quadrant West Longitude 20° to 0°, pages 54-66. London [England]: George Philip & Son, 1895.
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Available @ https://planetarynames.wr.usgs.gov/Feature/3686

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Available @ https://planetarynames.wr.usgs.gov/Feature/3691

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Available @ https://planetarynames.wr.usgs.gov/Feature/3691

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Available @ https://planetarynames.wr.usgs.gov/Feature/3691

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