Procellarum Twins
Explanation:
Western Oceanus Procellarum has few attractions because the relatively bland lava surface extends almost to the limb. But two nearly twin craters about 15 degrees north of the equator offer a number of observing challenges. Cardanus and Krafft are each about 50 km in diameter and each appears relatively fresh. But K.C.s near-terminator image shows that they have different relations with the adjacent Oceanus Procellarum. We can see that Krafft, the northernmost (left) twin, is older than the surrounding mare because the craters radial ejecta and rim deposits are covered by the lavas. Look further north and notice that Seleucus and Briggs are also surrounded by younger lava. Cardanus has a more complex relation. It has formed on an older and higher piece of lava, and its beautiful radial ejecta ridges are still preserved on that lava surface. A number of rilles also cross this old surface. However, on the left side of Cardanus, the older mare is abruptly truncated and smooth younger lava flowed right up to the crater rim. In fact, the area immediately northeast of Cardanus looks like there is another 50 km wide crater that has been completely buried by the younger lavas. Do you see it - it butts up against the odd crater chain (Catena Krafft) that links the twins? And also notice the contact between the older and younger lavas is quite distinct east of Cardanus where the surface texture and rilles abruptly stop.
