November 14, 2010
Younger And Older?
north to left LRO WAC image processed by Stefan Lammel, UK
This low Sun view of Rümker provokes new observations and resurrection of some old questions. First thought to be a degraded crater, Rümker finally became recognized as a pile of volcanic domes. The most recent study by Christian Wöhler, Raf Lena and K. C. Pau determined that Rümker rises about 1 km above the Procellarum lavas, with six individual domes about 100 to 200 meters tall. The low spot in the center helps explain why older observers mistook Rümker for a degraded crater. Another process that forms a depression in the center of a volcanic structure is collapse to form a caldera. That is possible, but perhaps the low spot is simply a place where domes didn't form. Along the top part of Rümker the surrounding mare lavas ride up against and perhaps a little over the dome complex. At the north (left in this view) end of Rümker it appears that the dome truncates the mare ridge, suggesting that Rümker is younger than this piece of the mare. Both Rümker and the maria that encircle it have various ages.
LRO WAC image M116696225ME
Rükl plate 8