Sulcus (geology)
![](../I/m/Medusae_Sulci_based_on_day_THEMIS.png)
Medusae Sulci based on day THEMIS day-time image on Mars
Sulcus (plural : sulci) is, in astrogeology, a long parallel groove on a planet or a moon.
For example, Uruk Sulcus is a bright region of grooved terrain adjacent to Galileo Regio on Jupiter's moon Ganymede.