AI 中文总结
本文通过考虑月球自转重新评估反极溅射物沉积，发现极地撞击时自转影响小，赤道撞击时影响显著，表明解释月球盆地反极磁异常时需重视自转效应。
AI 中文摘要
月球地壳存在强磁异常，可能记录了月球核发电机产生的古磁场。月球物质的磁化率较低，但高磁化率的撞击体物质可能记录了月球的古发电机磁场。部分磁异常与月球盆地呈反极分布，有假说认为撞击溅射物会在盆地反极处堆积，进而记录月球古磁场。此前的撞击模拟忽略了月球自转，支持该假说。本文重新评估考虑月球自转时反极溅射物的沉积情况，假设月球自转周期与当前相同，发现若撞击发生在极地附近，月球自转对反极溅射物沉积无显著影响；但对于赤道附近的撞击，自转对反极沉积有显著影响：东向撞击入射角为45度时几乎没有反极溅射物，而入射角为30度时，反极溅射物的堆积量比无自转情况更多。对于非椭球形和/或溅射毯不对称的盆地，很难确定撞击体的方向和位置。不过，本研究表明，在解释月球盆地反极处的磁异常时需谨慎，且不应忽略自转的影响。
英文摘要
The Moon's crust exhibits strong magnetic anomalies that likely record ancient magnetic fields produced by a core dynamo. Lunar materials have low magnetic susceptibility, but impactor material with high susceptibility may record the Moon's ancient dynamo. Some magnetic anomalies are antipodal to lunar basins and it is hypothesized that the impact ejecta accumulates at the basin antipode and records the ancient lunar magnetic field. Previous impact simulations, which ignored the rotation of the Moon, support this hypothesis. Here, we reevaluate the deposition of antipodal ejecta by considering the rotation of the Moon. Assuming that the rotational period of the Moon is the same as the current day, we find that the rotation of the Moon does not strongly affect the deposition of the antipodal ejecta if impacts occur near the poles. In contrast, rotation has a considerable effect on antipodal deposits for impacts occurring near the equator. An eastward impact at a 45 degree incidence angle results in almost no antipodal ejecta, however, an eastward impact with a 30 degree incidence angle accumulates more antipodal ejecta than the non-rotating case. It is hard to determine the impactor's direction and location, for basins without an ellipsoidal shape and/or an asymmetric ejecta blanket. Nevertheless, our work demonstrates that care must be taken in interpreting the magnetic anomalies antipodal to lunar basins and that the effect of rotation should not be ignored.
Comments20 pages, 9 figures, accepted for publication in JGR: Planets
