Hun Kal (crater)

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Hun Kal is a small impact crater on Mercury, about 1.1 km across. It serves as the reference point for Mercury’s longitude, with its center at 20° West, which defines the planet’s prime meridian. The name means "20" in Maya, chosen because the true 0° longitude area was in shadow in early Mariner 10 photos. The planet’s prime meridian runs through the hottest point on the equator, so it gets extra sunlight around perihelion. Hun Kal sits inside a larger unnamed crater. To the northwest is Al-Jahiz crater, and to the west is Lu Hsun crater. It lies in Mercury’s Kuiper quadrangle, near the equator (about 0° latitude) and at 20° West.