Lunar Domes in Delisle Region: Morphometry and Mode of Formation
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49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083) 1009.pdf Lunar domes in Delisle region: Morphometry and mode of formation. KC Pau1 and R. Lena2. 1 Flat 20A, Fook Chak House, 17 Po Yan Street, Hong Kong; [email protected]; 2Via Cartesio 144, sc. D, 00137 Rome, Italy- BAA Lunar section;[email protected] Introduction: Recent studies about lunar domes the examined domes by applying the combined are based on the evaluation of their spectrophotometric photoclinometry and shape from shading method (sfs) and morphometric properties, rheologic parameters, described in [1-4]. and their classification based on the spectral properties The heights of the domes De1 and De2 were de- and three dimensional shapes of the volcanic edifices termined to 108 ± 10 m and 95 ± 10 m, resulting in [1-3]. In this contribution we provide an analysis of flank slopes of 0.60° and 0.55° respectively (Fig. 5). two domes located in Delisle region near the crater Assuming a parabolic shape the estimated edifice vol- Artsimovich and Diophantus D, termed De1 and 2 umes correspond to about 23 and 24 km3 for the domes (Fig.1 and Table 1). De1 and De2. Fig. 2. WAC imagery: two domes are not apparent as in CCD telescopic image. Fig. 1. Telescopic image acquired on January, 8, 2017 at 13:35 UT with a 250 mm f/6 Newtonian reflector and a 2.5X barlow (Pau). General description and spectral properties: Delisle is an impact crater located in the western part of the Mare Imbrium. It lies to the north of the crater Diophantus, and to the northeast of the designated Mons Delisle (Figs. 1-2). The lavas of the examined mare domes are characterized by moderate TiO2 con- tent (Fig. 3). dome long. lat. slope D [km] h [m] V [km3] De1 -37.82° 26.80° 0.60° 22.4 108 23 Fig. 3. Clementine colour ratio image of the examined re- De2 -38.04° 28.43° 0.55° 24.0 95 24 gions with the domes De 1 and De 2 marked. Table 1: Morphometric properties of the examined domes. In the LOLA DEM [5], the elevation difference be- For both domes, Clementine UVVIS spectral data tween the domes centre and the surrounding surface is indicate a R415/R750 ratio of 0.576 indicating basalts of in good accordance with the image-based low TiO2 content (Fig. 3), and furthermore reveal a 750 photoclinometry and shape from shading analysis. The nm reflectance of R750 = 0.104 and a weak mafic ab- LOLA DEM data indicate a mare surface inclined from sorption for two domes with R950/R750 = 1.007. the southwest towards the north east. Moreover the two Morphometric dome properties: Based on the domes are well detectable in the rendered image of Fig. telescopic CCD image (Fig. 1) we obtained a DEM of 4. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083) 1009.pdf De 2, magma viscosities of 2.9 x 104 and 1.5 x 104 Pa s, and very short durations of the effusion process of 0.98 and 0.82 years, respectively (Table 3). Fig. 4. Rendered image based on the LOLA DEM using LTVT under the same solar illumination angle of the CCD image (Fig. 1). Fig. 6. Cross-sectional profile in east-west direction derived with the ACT-REACT Quick Map tool. De1 (Top) and De2 (Bottom). The examined domes near Delisle belong to class C1, as defined in [2-4], with a tendency towards class B2 due their red spectral appearance, large diameter and high edifice volumes. Furthermore, we estimated Fig. 5. Profiles obtained by the DEMs of De1 (top) and De 2 the magma rise speed U and the dike geometry (width W and length L). The domes are typical representative (bottom). The vertical axis is 20 times exaggerated. of rheologic group R1 characterised by lava viscosities 4 6 -5 -3 -1 According to the GLD100 data [6], the derived of 10 -10 Pa s, magma rise speeds U of 10 -10 m s , height of the two domes correpond to 100 and 90 m, dike widths W around 10-20 m, and dike lengths L for De1 and De2 respectively (Fig. 6). The elevation between about 30 and 150 km. Rheologic group R2 is 2 map of the domes, based on telescopic CCD imagery, characterised by low lava viscosities between 10 and 4 -3 -1 is suitable for the 3D reconstruction of the domes De 1- 10 Pa s, fast magma ascent (U > 10 m s ), narrow 2 since it extracts the height profile relative to the un- (W = 1-4 m) and short (L = 7-20 km) feeder dikes. The derlying surface, thus removing the mentioned overall third group, R3, is made up of domes which formed 6 8 inclination effect. from highly viscous lavas of 10 -10 Pa s, ascending at -6 -5 -1 dome E U W L very low speeds of 10 -10 m s through broad dikes η [Pa s] Te [m3 s-1] [years] [m s-1] [m] [km] of several tens to 200 m width and 100-200 km length. De1 2.9 x 104 815 0.98 2.0 x 10-3 10 44 De2 1.5 x 104 995 0.82 3.8 x 10-3 9 35 References: [1] Lena et al. (2007) Planet. Space Table 3: Rheologic properties and dike geometries inferred for Sci. 55, 1201-1217; [2] Wöhler et al. (2006) Icarus the examined domes. 183, 237-264; [3] Wöhler & Lena (2009) Icarus 204, 381-398; [4] Lena et al. (2013) Lunar domes: Proper- Rheologic properties: The rheologic model devel- ties and Formation Processes. Springer Praxis Books; oped in [7], yields estimates of the lava viscosity η, the [5] Smith et al. (2010) Space Sci. Revs. 150, 209-241, effusion rate E, and the duration T of the effusion pro- doi:10.1007/s11214-009-9512-y; [6] Scolten et al. cess for a monogenetic lava dome. Using the morpho- (2012) J. Geophys. Res. 117 (E00H17), metric values listed in Table 1, are obtained high effu- doi:10.1029/2011JE003926; [7] Wilson and Head sion rates of 815 and 995 m3 s-1 for the domes De 1 and (2002) J. Geophys. Res. 107 (E8). .