Lunar Non-Mare Volcanism: The Role Of Commercial Missions In The Exploration Of The Gruithuisen Domes
Introduction: The Gruithuisen domes are locat-ed at the outer rim of the Imbrium basin  in the NW portion of the Procellarum KREEP Terrane (PKT)  enhanced concentrations of Th . The domes represent distinctive spectral features on the Moon, the red spots [4 11]. The three, steep-sided mountains (NW, Gamma, and Delta) that are dis-tinctly different from mare-type domes [12,13]; the overall shape suggests that they formed by erup-tions of high-viscosity, SiO2-rich magmas , resembling the smaller features that characterize the Compton-Belkovich region , a distinctive Th anomaly outside PKT . Association with the Th-anomaly was interpreted as evidence for compositionally evolved lunar volcanism . In contrast, the Gruithuisen domes are much more prominent structures . CSFD on the summit plateaus of the G-γ and G-δ domes  indicate a similar age, ~3.8 Ga (G-γ) and 3.77 Ga (G-δ), con-sistent with those reported earlier [16,17]. Here we present a strategy for involvement of commercial spacecraft in the exploration of these types of fea-tures, focusing on the Gruithuisen domes designed to provide constraints on models of formation of non-basaltic volcanic features on the Moon. Dimensions: The Gruithuisen-NW dome is a rounded (~6.4x8 km) cone-like structure with steep (~15-20o, Fig. 1a) slopes. A break in slope at -1800 m contour marks the base of the dome and the top of the dome is at ~-600 km; its total height is ~1.2 km and the total exposed volume ~30 km3. The Gruithuisen-gamma (G-γ) dome is a flat-topped, slightly elongated mountain (~19x24.5 km), which is ~1.2 m high. Its exposed volume is ~130 km3. The base of the dome within the high-lands occurs at an elevation of ~-1900 m (Fig. 1b). The dome has a flat summit plateau (10x15 km) that is tilted northward and outlined by a promi-nent break in slope at ~-700 m. The pattern of the DTM contour lines indicates that flanks of the dome are mostly a series of facets with flat or slightly concave inward surfaces. The N and NE flanks of the dome are steeper, ~18-20o, than the S and SW flanks, ~11o (Fig.1a). Topographic pro-files show that the SW flank of the dome is slightly concave downward and a low (~100 m) scarp out-lines its base. Gruithuisen-delta (G-δ) is elongated in a NW di-rection (~35x18 km); it has a flat summit area con-sisting of a higher part (-300 m, NW side) and a lower part (-700 m, SE side). The maximum height of the dome is ~1.7 km and its total exposed vol-ume is estimated to be ~700 km3. The SW flank consists of a series of facets; facet slopes can be as steep as 15-20o (Fig. 1a). The NW and NE sides appear as broad lobes with lower, 7-9o, slopes. Strategy: We have outlined a series of Lander-Rover-Sample Return (L-R-SR) missions designed to land on the flat summits of the Gruithuisen-gamma (G-γ) and Gruithuisen-delta (G-δ) domes, document the surface morphological, mineralogi-cal, elemental and petrological characteristics lead-ing up to sample return, in order to resolve the im-portant questions about their petrogenesis and the thermal evolution of the Moon (19-20). References: 1) Head et al. LPSC-9, 488, 1978; 2) Jollif et al., JGR, 105, 4197, 2000; 3) Petro, NG, 4, 499, 2011; 4) Whitaker, The Moon, 4, 348, 1972; 5) Malin, EPSL, 21, 331, 1974; 6) Head, McCord, Science, 199, 1433, 1978; 7) Chevrel, S.D. et al. LPSC-25, 249, 1994; 8) Chevrel et al. LPSC-26, 241, 1995; 9) Chevrel et al. LPSC-27, 215, 1996; 10) Chevrel et al. JGR, 104, p. 16515, 1999; 11) Kusuma. et al. PSS 67, 46, 2012; 12) Head, Gifford, Moon, 22, 235, 1980; 13) Braden, et al. LPSC-41, #2677, 2010; 14) Wilson, J. Head, JGR, 108, 10.1029/2002JE001909, 2003; 15) Jolliff et al., NG, 4, 566, 2011; 16) Wagner et al. LPSC, #1619, 2002; 17) Wagner et al. JGR, 107, 10.1029/2002JE001844, 2002; 18) Neukum et al. SSR, 96, 55, 2001; 19. Wilson, Head, Icarus 283, 146, 2017; 20) Head, Wilson, Icarus, 283, 176, 2017. 21) Ivanov et al., Icarus 273, 262, 2016.