Hun Kal (crater)

Crater on Mercury

0°28′S 20°01′W / 0.46°S 20.01°W / -0.46; -20.01Diameter1.13 km (0.70 mi)Eponym'20' in the Mayan language

Hun Kal is a small (about 1.5 km in diameter) crater on Mercury that serves as the reference point for the planet's system of longitude. The longitude of Hun Kal's center is defined as being 20° W, thus establishing the planet's prime meridian.^[1] The name "Hun Kal" means '20' in the language of the Maya.^[2]

Hun Kal was chosen as a reference point since the actual prime meridian was in shadow when Mariner 10 photographed the region, hiding any features near 0° longitude from view.

The prime meridian of Mercury is thermocentric, it runs through the point on the equator where the planet is hottest (due to the planet's rotation and orbit, the sun briefly retrogrades at noon at this point during perihelion, giving it more sun).^[3]^[4]^[5]

The large crater in which Hun Kal lies is not named. To the northwest is Al-Jāhiz crater, and to the west is Lu Hsun crater.

This Mariner 10 image shows the surrounding context of Hun Kal, which is almost invisibly tiny near the center.
MESSENGER NAC image with Hun Kal at center

References

^ "USGS Astrogeology: Rotation and pole position for the Sun and planets (IAU WGCCRE)". Archived from the original on 24 October 2011. Retrieved 22 October 2009.
^ "Hun Kal". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
^ Davies, M. E., "Surface Coordinates and Cartography of Mercury," Journal of Geophysical Research, Vol. 80, No. 17, June 10, 1975.
^ Archinal, Brent A.; A'Hearn, Michael F.; Bowell, Edward L.; Conrad, Albert R.; et al. (2010). "Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2009". Celestial Mechanics and Dynamical Astronomy. 109 (2): 101–135. Bibcode:2011CeMDA.109..101A. doi:10.1007/s10569-010-9320-4. ISSN 0923-2958. S2CID 189842666.
^ "USGS Astrogeology: Rotation and pole position for the Sun and planets (IAU WGCCRE)". Archived from the original on October 24, 2011. Retrieved October 22, 2009.

Mercury

Outline

Geography

General	Albedo features Atmosphere Features Magnetic field
Regions	Quadrangles
Quadrangles	Bach Beethoven Borealis Debussy Derain Discovery Eminescu Hokusai Kuiper Michelangelo Neruda Shakespeare Raditladi Tolstoj Victoria
Mountains and volcanoes	Caloris Montes
Plains and plateaus	Apārangi Planitia Borealis Planitia Budh Planitia Caloris Planitia Mearcair Planitia Odin Planitia Sobkou Planitia Stilbon Planitia Suisei Planitia Tir Planitia Utaridi Planitia
Canyons and valleys	Arecibo Catena Arecibo Vallis Goldstone Catena Goldstone Vallis Haystack Catena Haystack Vallis Simeiz Vallis
Ridges and rupes	Antoniadi Dorsum Adventure Rupes Beagle Rupes Discovery Rupes Enterprise Rupes Hero Rupes Resolution Rupes Santa María Rupes Victoria Rupes
Basins and fossae	Caloris Basin Pantheon Fossae Raditladi Basin Rembrandt Basin Skinakas (hypothetical basin)
Craters	Abedin Abu Nuwas Africanus Horton Ahmad Baba Ailey Aksakov Akutagawa Al-Akhtal Alencar Al-Hamadhani Al-Jāhiz Alver Amaral Amru Al-Qays Andal Aneirin Angelou Anguissola Anyte Apollodorus Aristoxenes Aśvaghoṣa Atget Bach Balagtas Balanchine Baranauskas Balzac Bartók Barma Bashō Beckett Beethoven Bek Belinskij Bello Benoit Berkel Bernini Bjornson Boccaccio Boethius Botticelli Brahms Bramante Brontë Bruegel Brunelleschi Burns Byron Callicrates Camões Carducci Carolan Calvino Cervantes Cézanne Chaikovskij Chao Meng-Fu Chekov Chiang Kʻui Chŏng Chʼŏl Chopin Chu Ta Coleridge Copland Copley Couperin Cunningham Dali Dario De Graft Debussy Degas Delacroix Derain Derzhavin Desprez Dickens Dominici Donne Dostoevskij Dowland Durer Dvorak Eastman Eitoku Eminescu Enheduanna Enwonwu Equiano Faulkner Fet Firdousi Flaubert Flaiano Futabatei Gainsborough Gauguin Geddes Ghiberti Gibran Giotto Glinka Gluck Goethe Gogol Goya Grieg Guido d'Arezzo Hals Han Kan Handel Harunobu Hauptmann Hawthorne Haydn Heine Hemingway Hesiod Hiroshige Hitomaro Hodgkins Hokusai Holbein Holberg Holst Homer Horace Hovnatanian Hugo Hun Kal Hurley Ibsen Ictinus Imhotep Ives Izquierdo Janáček Jokai Judah Ha-Levi Kalidasa Karsh Keats Kenko Kertész Khansa Kipling Kōshō Kuan Han-Chʻing Kuiper Kulthum Kunisada Kurosawa Lange Larrocha Leopardi Lermontov Lessing Li Chʻing-Chao Li Po Liang Kʻai Liszt Lovecraft Lu Hsun Lysippus Ma Chih-Yuan Machaut Mahler Mansart Mansur March Mark Twain Martí Martial Matabei Matisse Melville Mena Mendes Pinto Michelangelo Mickiewicz Milton Mistral Mofolo Molière Monet Monteverdi Moody Mozart Munch Munkácsy Murasaki Mussorgskij Myron Nabokov Nampeyo Navoi Nawahi Neruda Nureyev Nervo Neumann Nizami Okyo Oskison Ovid Petrarch Phidias Picasso Poe Polygnotus Praxiteles Prokofiev Qi Baishi Rachmaninoff Raden Saleh Raditladi Rameau Raphael Rembrandt Renoir Rivera Rizal Rodin Rudaki Sander Scarlatti Schubert Shakespeare Sholem Aleichem Sinan Stravinsky Sullivan Sveinsdóttir Titian To Ngoc Van Tolstoj Velázquez Verdi Villa-Lobos Vivaldi Vyasa Xiao Zhao Yeats Zola
Other	Geology Ghost craters Inter-crater plains

Moons

Hypothetical moon of Mercury

Astronomy

Transits	Earth Mars
Asteroids	Mercury-crossing asteroids

Exploration

Current and past	Mariner 10 (1973–1975) MESSENGER (2004–2015) BepiColombo (2018–present)
Proposed	Mercury-P (~2031)
See also	Colonization of Mercury