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<p>Planetary impacts not only reshape planetary surfaces but also fundamentally alter rock properties at the nanoscale. By analyzing the Hammadah al Hamra 346 (HaH 346) chondrite containing shock melt veins, we find that shock not only causes the transformation of some minerals into high-pressure phases (wadsleyite and jadeite) but also induces grain refinement. The average crystal grain size decreases from 16.71&#xa0;μm to 0.74&#xa0;μm, resulting in an increase of ~ 70% in the elastic modulus and hardness of all minerals, including both high-pressure and non-high-pressure phases. At the rock scale, mechanical behavior is controlled by a competition between mineral strengthening and crack weakening. When contraction cracks are present and dominant, the mechanical strength and P-wave velocity of rocks are reduced, consistent with observations from the Charlevoix and Chesapeake Bay impact structures. In contrast, in the absence of such cracks, mineral strengthening dominates, leading to increases of 20–50% in rock mechanical strength and P-wave velocity. This study establishes a cross-scale framework that links crystal grains, mineral grains, and rocks, revealing how impact processes influence the physical–mechanical properties of planetary surfaces.</p>

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Mineral Strengthening and Crack Weakening Jointly Control the Physical–mechanical Properties of Shocked Planetary Rocks

  • 期刊论文

  • 发表日期：

    2026年7月10日

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  • Yiheng Zhang,
  • Jiangmei Qiao,
  • Haifeng Zhao,
  • Pengzhi Pan,
  • Xuhai Tang

摘要

Planetary impacts not only reshape planetary surfaces but also fundamentally alter rock properties at the nanoscale. By analyzing the Hammadah al Hamra 346 (HaH 346) chondrite containing shock melt veins, we find that shock not only causes the transformation of some minerals into high-pressure phases (wadsleyite and jadeite) but also induces grain refinement. The average crystal grain size decreases from 16.71 μm to 0.74 μm, resulting in an increase of ~ 70% in the elastic modulus and hardness of all minerals, including both high-pressure and non-high-pressure phases. At the rock scale, mechanical behavior is controlled by a competition between mineral strengthening and crack weakening. When contraction cracks are present and dominant, the mechanical strength and P-wave velocity of rocks are reduced, consistent with observations from the Charlevoix and Chesapeake Bay impact structures. In contrast, in the absence of such cracks, mineral strengthening dominates, leading to increases of 20–50% in rock mechanical strength and P-wave velocity. This study establishes a cross-scale framework that links crystal grains, mineral grains, and rocks, revealing how impact processes influence the physical–mechanical properties of planetary surfaces.