瑞士苏黎世联邦理工学院Khan, A.和Huang, D.课题组的一项最新研究揭示了火星地核顶部存在液态硅酸盐层的证据。2023年10月25日，国际知名学术期刊《自然》发表了这一成果。

该研究组展示了沿着火星分层地核-地幔边界区域的多重衍射 P 波，结合富铁液态合金热弹性性质的第一性原理计算，需要覆盖在更小、密度更大的液态核上的完全熔融硅酸盐层。相对于先前的模型，当熔融硅酸盐层的厚度和密度为 150±15km 和4.05±0.05g cm^-3 时，反演对地核—地幔边界区域特别敏感的差分体波传播时间，数据表明火星地核半径减少 1,650±30km ，密度增加 6.65±0.1g cm^-3。

这里推断的地核性质符合整体地球物理和宇宙化学要求，地核含有 85-91wt% 的铁镍和 9-15wt% 的轻元素，主要是硫、碳、氧和氢。地核上方熔融硅酸盐层的化学特征可能是火星岩浆活动的产物。

研究人员表示，洞察号任务期间的地震记录表明，火星的液态核心需要比纯液态铁轻约 27%，这意味着火星的液态核心有相当多的轻元素。然而，与可能构成火星板块的宇宙化学成分相比，基于地震和整体地球物理限制的地核成分可获得的挥发性元素氢、碳和硫的数量更多。

附：英文原文

Title: Evidence for a liquid silicate layer atop the Martian core

Author: Khan, A., Huang, D., Durn, C., Sossi, P. A., Giardini, D., Murakami, M.

Issue&Volume: 2023-10-25

Abstract: Seismic recordings made during the InSight mission suggested that Mars’s liquid core would need to be approximately 27% lighter than pure liquid iron, implying a considerable complement of light elements. Core compositions based on seismic and bulk geophysical constraints, however, require larger quantities of the volatile elements hydrogen, carbon and sulfur than those that were cosmochemically available in the likely building blocks of Mars. Here we show that multiply diffracted P waves along a stratified core–mantle boundary region of Mars in combination with first-principles computations of the thermoelastic properties of liquid iron-rich alloys require the presence of a fully molten silicate layer overlying a smaller, denser liquid core. Inverting differential body wave travel time data with particular sensitivity to the core–mantle boundary region suggests a decreased core radius of 1,675±30km associated with an increased density of 6.65±0.1g cm^-3, relative to previous models, while the thickness and density of the molten silicate layer are 150±15km and 4.05±0.05g cm^-3, respectively. The core properties inferred here reconcile bulk geophysical and cosmochemical requirements, consistent with a core containing 85–91wt% iron–nickel and 9–15wt% light elements, chiefly sulfur, carbon, oxygen and hydrogen. The chemical characteristics of a molten silicate layer above the core may be revealed by products of Martian magmatism.

DOI: 10.1038/s41586-023-06586-4

Source: https://www.nature.com/articles/s41586-023-06586-4