日本东京科学研究所Hyodo Ryuki团队最新的研究，揭示了微流星体撞击期间土星环粒子具有抗污染的特性。2024年12月16日出版的《自然—地球科学》杂志发表了这项成果。
根据非冰微流星体的轰击会随着时间的推移使土星环变暗的假设，土星环的年龄被估计大约在1亿到4亿年之间。卡西尼号的观测表明，土星环的颗粒似乎相对干净。这些年轻的年龄估计假设土星环是由纯水冰粒子形成的，且撞击非冰微流星体物质的吸积效率很高（η10%）。
研究人员展示了超速微流星体撞击环粒子的数值模拟，表明非冰物质可能不像以前认为的那样容易聚集。结果发现，在与土星环粒子的高能碰撞中，非冰撞击物质的完全汽化和膨胀导致带电纳米粒子和离子的形成。通过与土星的碰撞、引力逃逸或电磁拖拽进入土星的大气层，这些粒子和离子随后从土星环中被移除。
尽管该模型存在不确定性，其假设没有孔隙度、强度或环颗粒粒度，但研究人员认为，微流星体撞击后，会发生非冰物质的最小增生。这种抗污染机制意味着吸积效率较低（η1%）。因此，研究人员认为土星环表面上的年轻可能是由于其具抗污染性，而不是年轻形成时间的标志。
附：英文原文
Title: Pollution resistance of Saturn’s ring particles during micrometeoroid impact
Author: Hyodo, Ryuki, Genda, Hidenori, Madeira, Gustavo
Issue&Volume: 2024-12-16
Abstract: Saturn’s rings have been estimated to be as young as about 100 to 400 million years old according to the hypothesis that non-icy micrometeoroid bombardment acts to darken the rings over time and the Cassini observation indicated that the ring particles appear to be relatively clean. These young age estimates assume that the rings formed out of pure water ice particles with a high accretion efficiency of impacting non-icy micrometeoroid material (η10%). Here we show, using numerical simulations of hypervelocity micrometeoroid impacts on a ring particle, that non-icy material may not be as readily accreted as previously thought. We found that the complete vaporization and expansion of non-icy impactor material on energetic collision with a ring particle leads to the formation of charged nanoparticles and ions that are subsequently removed from the rings through collision with Saturn, gravitational escape or electromagnetic drag into Saturn’s atmosphere. Despite uncertainties in our models that assume no porosity, strength or ring particle granularity, we suggest minimal accretion of non-icy materials would occur following micrometeoroid impact. This pollution resistance mechanism implies a low accretion efficiency (η1%). Thus we suggest that the apparent youth of Saturn’s rings could be due to pollution resistance, rather than indicative of young formation age.
DOI: 10.1038/s41561-024-01598-9
Source: https://www.nature.com/articles/s41561-024-01598-9