Kerwan (crater)

Kerwan is a large impact crater located on the Saturnian moon Iapetus. It is one of the most prominent features on Iapetus, and a significant contributor to the moon's distinctive two-toned appearance.

Description:

Kerwan is approximately 440 kilometers (270 miles) in diameter, making it comparable in size to Iapetus itself, which has a diameter of about 1,470 kilometers (910 miles). The crater's rim is relatively subdued and eroded, indicating that it is a very old feature. The crater floor is relatively smooth, possibly due to infilling from later impacts or other geological processes.

Location:

Kerwan is situated in the leading hemisphere of Iapetus, the side that faces forward as the moon orbits Saturn. Its central coordinates are approximately 11° N latitude, 272° W longitude.

Formation:

Kerwan is believed to have been formed by a massive impact event early in Iapetus's history. The size of the crater suggests that the impacting object must have been quite large. The impact likely excavated a significant amount of material, which may have contributed to the formation of the equatorial ridge that runs along Iapetus's equator. The contrasting albedo (reflectivity) of Iapetus, with the dark Cassini Regio on the leading hemisphere, is hypothesized to be related to the Kerwan impact. One theory suggests that the impact excavated subsurface ice, which subsequently sublimated, leaving behind a lag deposit of darker material.

Significance:

Kerwan is important for understanding the geological history of Iapetus and the Saturnian system. Its size and location provide valuable insights into the bombardment history of the outer Solar System and the processes that have shaped the surfaces of icy moons.