A compositionally heterogeneous martian mantle due to late accretion
A compositionally heterogeneous martian mantle due to late accretion
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由于晚期吸积而形成的成分异质的火星地幔
DOI：
10.1126/sciadv.aay2338
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发表时间：
2020
期刊：
影响因子：
13.6
通讯作者：
R. Canup
中科院分区：
文献类型：
--
作者：
S. Marchi;R. Walker;R. Canup
火星上的一些早期的大型碰撞可能是造成火星陨石中钨和铂的异质性的原因。火星地幔中高亲铁元素（HSE）的近似球粒状估计相对丰度表明这些元素是在火星核心形成后添加的。 Shergottite-nakhlite-chassigny (SNC) 陨石意味着平均地幔 Pt 丰度约为十亿分之 3 至 5，这需要在硅酸盐火星中添加 1.6 × 1021 千克球粒状物质，或 0.25% 的火星质量。在这里，我们提出了平滑粒子流体动力学撞击模拟，表明火星的 HSE 丰度意味着大型差异射弹的一到三次后期碰撞。我们证明这些碰撞会产生成分异质的火星地幔。主要基于 W 同位素，有人认为火星仅在大约 2 至 4 百万年（Ma）内就迅速增长。然而，我们发现，具有不同分馏 Hf/W 和不同 182W 的地幔域的撞击生成可能意味着火星形成时间尺度高达 15 Ma。
A few early, large collisions on Mars may be responsible for heterogeneity in tungsten and platinum in martian meteorites. The approximately chondritic estimated relative abundances of highly siderophile elements (HSE) in the bulk martian mantle suggest that these elements were added after Mars’ core formed. The shergottite-nakhlite-chassigny (SNC) meteorites imply an average mantle Pt abundance of ≈3 to 5 parts per billion, which requires the addition of 1.6 × 1021 kilograms of chondritic material, or 0.25% martian masses, to the silicate Mars. Here, we present smoothed particle hydro-dynamics impact simulations that show that Mars’ HSE abundances imply one to three late collisions by large differentiated projectiles. We show that these collisions would produce a compositionally heterogeneous martian mantle. Based mainly on W isotopes, it has been argued that Mars grew rapidly in only about 2 to 4 million years (Ma). However, we find that impact generation of mantle domains with variably fractionated Hf/W and diverse 182W could imply a Mars formation time scale up to 15 Ma.