Hun Kal (crater)

Hun Kal is a 7-kilometer-diameter impact crater located on the planet Mercury. It is notable for being the location of the prime meridian, or 0° longitude, on the planet. The name "Hun Kal" comes from the Mayan word for "twenty," as Mayan astronomers used a base-20 numerical system. This connection to the number twenty was chosen to reflect the crater's position defining the planet's longitudinal reference point, much like the number zero is fundamental to many mathematical systems. The crater exhibits a relatively simple bowl shape, indicating it is a geologically young feature compared to other craters on Mercury's heavily cratered surface. Hun Kal is situated within the larger, much older Caloris Basin.