domenica 6 luglio 2014

Birt and Rupes Recta region
Birt bisected domes (termed Birt 1-2)

by Mike Wirths

by Mike Wirths

by Mike Wirths
by George Tarsoudis

Diameter [km]
Heigth [m]
Birt 1
Birt 2
16.0 ± 0.5
7.8 ± 0.5
  170 ± 20
   70 ± 10
1.2 ± 0.1
1.0 ± 0.1

Two bisected domes near the crater Birt in Mare Nubium are situated at the northern end of Rima Birt, supporting a volcanic origin of the rille. It is a slightly curved rille of more than 50 km length and displays an offset in its central section. Rima Birt, the major axes of the vents of the domes, the outflow channel of Birt 1, and the linear rille associated with Birt 2 are oriented in parallel, approximately in the same direction as Rupes Recta and thus radial to the Imbrium basin. The formation of the different parts of Rima Birt is likely related to the stress field resulting from the ascent of one or several dikes to shallow depth below the surface, where some of the intruded magma reached the surface and formed the low domes B1 and B2. Birt 1 belongs to class C1, while Birt 2 belongs to class C1 with a tendency towards class C2 due to its smaller diameter and lower edifice volume.