Lunar mare basalts represent melting of mantle material, buoyant ascent in dikes, and eruption onto <20% of the surface. Global mare distribution is distinctly asymmetrical, with a paucity on the farside, plausibly interpreted to be related to thicker farside low-density crust inhibiting buoyant magma rise to the surface. Challenging this hypothesis is the presence of the huge, ancient farside South Pole-Aitken (SPA) basin, site of the thinnest crust and deepest depression observed on the Moon. We hypothesize that an oblique impact stripped the farside crust within the SPA basin, permitting early mare basalt emplacement as cryptomaria due to thin/absent crust. However, removal of the SPA thermally insulating megaregolith/crust accelerated lithosphere thickening beneath the basin. This deepening rheological barrier inhibited buoyant rise of mantle diapirs below SPA, resulting in early abatement of mare basalt extrusions compared to the nearside, and retention of the deep, underfilled SPA impact basin observed today.

中文翻译：

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月球近侧-远侧滨海玄武岩不对称性：全球地壳厚度变化和南极-艾特肯 （SPA） 盆地诱导的岩石圈增厚的综合作用


月海玄武岩代表地幔物质的熔化、堤坝的浮力上升以及喷发到地表的 <20%。全球海马分布明显不对称，远侧分布稀少，可以合理地解释为与较厚的远侧低密度地壳抑制浮力岩浆上升到地表有关。挑战这一假设的是巨大而古老的远侧南极-艾特肯 （SPA） 盆地的存在，该盆地是月球上观察到的最薄的地壳和最深的凹陷所在地。我们假设倾斜撞击剥离了 SPA 盆地内的远侧地壳，由于地壳薄/不存在，允许早期母马玄武岩放置为隐生岩。然而，去除 SPA 隔热巨型风化层/地壳加速了盆地下方岩石圈的增厚。这种加深的流变屏障抑制了 SPA 以下地幔底辟的浮力上升，导致与近侧相比，母马玄武岩挤压物的早期减少，并保留了今天观察到的深层、填充不足的 SPA 冲击盆地。