image by Bob Pilz
There would not have been any warning and probably nothing to see when a projectile came in low over the western horizon and plunged into Palus Somni, a bright region just west of Mare Crisium. To excavate the 28 km diameter crater Proclus the projectile was roughly 1 to 1.5 km wide and traveled a few kilometers per second. Its forward momentum caused ejecta to move sideway and forward – downrange – leaving a zone of avoidance uprange. Interestingly, the downrange rays seem to be in discrete swaths with gaps in between. Proclus is an atypical 28 km wide crater. Most craters that large have central peaks surrounded by a small flat floor and a few slump bulges on the edge of the floor. But Proclus has a floor completely full of debris that had slid down the slopes. It is not at all clear if the oblique impact that created the asymmetric rays somehow caused the unexpected interior. Hmm.
12 January 2006, 04:52 UT. Takahashi FSQ-106mm refractor, 5x Televue Powermate, DMK 21BF04 B/W Firewire camera, Blue IR-block filter - Recorded at 30fps, 1/64sec exposure, 6000 frames - Seeing 7-8/10, Transparency 9/10 - Processed in Registax (600/6000 frames stacked), ImagesPlus and Photoshop CS
Rükl chart 26
Apollo 15 Pan camera view