The mysteries of Mons Rumker

Mons Rumker
Sketch and Details by Richard Handy

Mons Rumker sits in isolation on the dark basalts of northwest Oceanus Procellarum like a lonely sentinel on the edge of some vast undiscovered wilderness. The Rumker Hills dome complex, situated on the western flank of the Aristarchus Plateau, lies on the top of a local swelling that is about 140 km in diameter. It is composed of a remarkable set of about a dozen volcanic domes and low mounds, which are scattered in a rough semi-circular plateau approximately 70 km in diameter. The surficial domes apparently overlay preexisting low domes so that the elevated northwest sections have a pancake like appearance. Despite the long shadows when viewed close to the terminator, nowhere do these domes rise much above 500 meters in elevation from the mean surface of the mare. A central depression to the southeast of the domed crescent displays a strange dichotomy between its darker and lighter floor that is very reminiscent of areas on the Moon that have pyroclastic deposits. The mysteries of Rumker are manifold: why is this the only such layered dome field on the surface of the Moon? Why is located here? Does it predate the mare lavas or is it the representative of the last vestiges of differentiated magmas that ended the mare sequences in this area? Is the central depression part of a preexisting separate domain or were both aspects, both domes and depression deposits, created over the same period of time?

Sketch details

Subject: Mons Rumker and environs Rukl: 8
Date: 3-31-07
Session Start 8:03 UT End 9.48 UT
Seeing: Antoniadi II-III Weather clear
Lunation 1042, 12.3 days Phase: 25.2 deg Illumination 95.2%
Colongitude: 60.7 deg
Lib in Lat: +00 deg 05 min Lib. in Long: +04 deg 04 min
Telescope: Meade 12” SCT f/10
Binoviewer: W.O. Bino –P with 1.6X nosepiece
Eyepieces: 12.4 mm Meade Super Plossls
Magnification: 393X
Sketch medium: White Conte’ Crayon on black textured Strathmore paper
Sketch size: 18” x 24”