Messier region

Messier domes (termed Messier 1-7) and Goclenius dome (termed Goclenius 1)

By George Tarsoudis

By Frank Schenck

By Jim Phillips

By Paolo Lazzarotti

By Raffaello Lena

Dome	long. [°]	lat. [°]	slope [°]	D [km]	h [m]	class
Me1	43.47	-1.95	1.26±0.15	7.7±0.3	85±10	C2-C1
Me2	50.42	-2.50	1.12±0.15	8.7 x 6.4±0.3	80±10	C2-C1
Me3	49.11	-2.70	0.87±0.1	10.7 x 9.0±0.3	80±10	In2
Me4	50.83	-2.16	3.2±0.3	5.6±0.3	160±20	C2-B1
Me5	51.60	-2.19	1.6±0.16	5.6±0.3	85±10	C2
Me6	49.80	-1.70	1.5±0.15	7.7±0.3	100±10	C2
Me7	51.48	-1.64	0.5±0.1	15.0±0.3	70±10	C1
Go1	45.40	-6.60	0.7±0.1	35.0±0.3	212±20	D

Two domes near Messier, which are similar to each other with respect to their morphometric, rheologic, and spectral properties, belong to class C2 with a tendency towards class C1 due to their moderate R415/R750 value. With their inferred moderate lava viscosittoies these domes share the properties of rheologic group R1. Accordingly, the inferred magma rise speed amounts to several 10-4 m/s and their feeder dikes were 10–12 m wide and 45–54 km long. The dome Me4 belongs class C2-B1,  Me5 and Me6 belong to class C2 while Me7 belongs to class C1. The lavas that form Mare Fecunditatis are believed to be relatively thin, with depths of 500 m but locally extending to 1500 m. This view is supported by the widespread occurrence of 'ghost craters' where the relatively low volumes of mid to late Imbrian lavas erupted have not obliterated the pre-existing crater population. This   has   allowed   a   glimpse   into   the   relationship   between   these craters and volcanic structures whether of an intrusive (Me3) or an effusive nature (Me1, 2, 4, 5, 6 and 7). It is apparent that the presence of these volcanic features associated with 'ghost craters' suggests a formative influence of one on the other, with ascending lavas exploiting the crustal fractures produced during the crater forming process, or the breccia lens/crater floors to produce sub-surface magma chambers which then fed effusive surface activity (Me3). It is   possible   that   some   of   the   mare   filled   basin   originally   looked   like   Mare Fecunditatis,  but   then   protracted   eruption   of   basalt   lavas,   compared   to Fecunditatis drowned this early landscape.  Two cones (Cones 1 to the north and Cone 2 to the south) are located on the summit of Me3, with diameters of about 1.9 km ± 0.3 km heights of 120 m ± 10 m and flank slopes of about 7.2° ± 0.7°. Their presence implies explosive activity. The dome Go1 is situated to the north east of the crater Goclenius and has a base diameter of 35 ± 0.5 km. A group of hills are located on the top. The northern section rises at an elevation of 160 m. Its height, determined using the cross-sectional profile in E-W direction  amounts to 212 ± 20 m, while the average slope angle  corresponds to 0.70° ± 0.07°. Its edifice volume was estimated of 90 km3, assuming a parabolic shape. The PCA analysis based on the spectral and morphometric data displays that Go1 is situated at the border of class D, possible indicating an origin by subsequent and different eruptions of lava. Edifices of more complex morphology, displaying large diameters above 20 km, low flank slopes, and very high edifice volumes, are represented by class D. Examples of dome of class D are Arago α and β in western Mare Tranquillitatis. In this scenario initially the dome Go1 formed from lava eruption with lower-Ti content (older red lava unit) followed by another effusive episode originated from lava effusion with higher titanium content, the youngest volcanic unit (blue lava) identified in Mare Fecunditatis. This second effusive activity interested principally the central and southern region of Go1, while the underlying basalt unit is exposed by impact craters penetrating the younger upper basaltic soil.