A dry lunar mantle reservoir for young mare basalts of Chang’e-5

Abstract

The distribution of water in the Moon's interior carries key implications for the origin of the Moon 1 , the crystallisation of the lunar magma ocean 2 , and the duration of lunar volcanism 2 . The Chang'E-5 (CE5) mission returned the youngest mare basalt samples, dated at ca. 2.0 billion years ago 3 , from the northwestern Procellarum KREEP Terrane (PKT), providing a probe into the spatio-temporal evolution of lunar water. Here we report the water abundance and hydrogen isotope composition of apatite and ilmenite-hosted melt inclusions from CE5 basalts, from which we derived a maximum water abundance of 370 ± 30 g.g -1 and a δD value (-330 ± 160‰) for their parent magma. During eruption, hydrogen degassing led to an increase in the D/H ratio of the residual melts up to δD values of 300-900‰. Accounting for low degrees of mantle partial melting followed by extensive magma fractional crystallisation 4 , we estimate a maximum mantle water abundance of 2-6 g.g -1 , which are too low for water contents alone to account for generating the Moon's youngest basalts. Such modest water abundances for the lunar mantle are at the lower end of those estimated from mare basalts that erupted from ca. 4.0-2.8 Ga 5, 6 , suggesting the mantle source of CE5 basalts dried up by ca. 2.0 Ga through previous melt extraction from the PKT mantle during prolonged volcanic activity.Water abundance in the lunar mantle places strict constraints on high-temperature processes, including the Moon-forming giant impact 1 , the ensuing crystallisation of the lunar magma ocean 7 , and the longevity of volcanism on the Moon 2 . Based upon the analyses carried out since the Apollo era, the Moon was long thought to be an anhydrous body. Advances in in situ analytical techniques over the past decade have allowed analysis of water abundances at micro-scale in various lunar samples, including in olivine-and pyroxene-hosted melt inclusions in mare basalts [8][9][10][11][12] , apatite in mare basalts and highlands samples [13][14][15][16][17][18][19][20] , pyroclastic glass beads 21, 22 , and

Chang’E-5 reveals the Moon's secrets to a longer life

“…Backstripping these effects, a maximum water abundance of 1-5 mg g À1 is estimated for the mantle source of the Chang'E-5 basalts. 5 Compared with Apollo basalts from ca. 4.0-2.8 Ga, the very modest water abundances of the mantle source of the Chang'E-5 basalts are among the lowest measured.…”

High-Spatial-Resolution Measurement Of Water Content In Olivine Using NanoSIMS 50L

“…19 More recently, in situ analysis of water content using SIMS has played an everexpanding role. 3,7,9,19,21,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] SIMS facilitates detecting multielements/isotopes simultaneously and measuring water content at tens to a few ppm levels. 3,7,9,19,21,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] Particularly, NanoSIMS could offer a higher spatial resolution and a lower background for water content analysis than conventional SIMS.…”

“…3,7,9,19,21,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] SIMS facilitates detecting multielements/isotopes simultaneously and measuring water content at tens to a few ppm levels. 3,7,9,19,21,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] Particularly, NanoSIMS could offer a higher spatial resolution and a lower background for water content analysis than conventional SIMS. On the one hand, the unique co-axial design of NanoSIMS reduces the spot size, which permits the analysis of much smaller minerals and mapping of the elemental distribution in crystal micro-structures.…”

“…On the one hand, the unique co-axial design of NanoSIMS reduces the spot size, which permits the analysis of much smaller minerals and mapping of the elemental distribution in crystal micro-structures. 9,27,28,31,[38][39][40][41][42][43][44][45][46] On the other hand, NanoSIMS has a smaller analysis chamber which is helpful in decreasing the chamber vacuum and thus, the hydrogen background. Although previous studies have reduced the background for water analysis to < 10 ppm by using NaonSIMS, the spatial resolution was restricted to > 10 μm.…”

Reconstructing The Color 3D Tomography Of Lunar Samples

“…These new samples provide vital data for the precise development of lunar soil models, evolution, calibrations, and verifications. [1][2][3][4] In general, nondestructive measurements are first implemented for the analysis of lunar samples because of their ability to retain the original morphology and composition of the rare samples. Among them, optical testing is the key non-contact procedure that can quickly record vivid tomography and color information from a sample.…”