Hun Kal (crater)

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Hun Kal
Hun Kal crater on Mercury cropped.png
Hun Kal is indicated by an arrow.
Planet Mercury
Coordinates 0°30′S 20°00′W / 0.5°S 20°W / -0.5; -20Coordinates: 0°30′S 20°00′W / 0.5°S 20°W / -0.5; -20
Diameter 1.5 km
Eponym '20' in the Mayan language

Hun Kal is a small 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]

This image shows the surrounding context of Hun Kal, which is almost invisibly tiny near the center.

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.

Hun Kal is about 1.5 km in diameter.[2]

The name "Hun Kal" means '20' in the language of the Maya.


  1. ^ "USGS Astrogeology: Rotation and pole position for the Sun and planets (IAU WGCCRE)". Retrieved 22 October 2009. 
  2. ^ "Hun Kal". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.