A recent large‐scale map of the lunar crustal magnetic field is examined for the existence of magnetic anomalies internal to ringed impact basins. It is found that, of 25 basins with upper preNectarian and younger ages, 18 contain mapped internal anomalies with amplitudes of at least 1 nT at 30 km altitude. Of these, five are most confidently judged to contain intrinsic anomalies (i.e., anomalies located within the inner basin rims and originating at the times of basin formation): Crisium, Humboldtianum, Mendel‐Rydberg, Moscoviense, and Nectaris. Comparing the anomaly distributions with previous numerical simulations of the impact of iron‐rich planetesimals to form a large (SPA‐sized) basin, inferences are drawn about the likely trajectories of the impactors. Specifically, results suggest that impactor trajectories for these basins were within ∼45° of being vertical and tended to lie on average parallel to the lunar equatorial plane and the ecliptic plane. Inverse modeling of anomalies within these basins yields inferred directions of magnetization that are difficult to reconcile with the axial centered dipole hypothesis for the geometry of the internal lunar dynamo field: Paleomagnetic pole positions are widely scattered and, in agreement with a recent independent study, the two main anomalies within Crisium yield significantly different directions of magnetization.

中文翻译：

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五个月球撞击盆地的磁异常：对撞击轨迹和反演的影响

检查了最近的月球地壳磁场大图，以了解环形撞击盆地内部是否存在磁异常。研究发现，在25个盆地中，有较高的早侏儒年龄和较年轻年龄的盆地，其中18个在30 km的高度处具有至少1 nT振幅的内部映射异常。其中，最有把握地断定其中有五个异常（即位于盆地内缘的异常，并且起源于盆地形成时的异常）：Crisium，Humboldtianum，Mendel-Rydberg，Moscoviense和Nectaris。将异常分布与富铁行星对形成大型（SPA大小）盆地的影响的先前数值模拟进行比较，得出有关撞击器可能轨迹的推论。具体来说，结果表明，这些盆地的撞击轨迹在垂直方向的约45°范围内，并且趋向于平均平行于月球赤道平面和黄道平面。在这些盆地内反演的异常模型会得出推断的磁化方向，这些方向很难与内部月球磁场的几何形状的轴向中心偶极子假设相一致：古磁极的位置分布广泛，并且与最近的独立研究一致， s内的两个主要异常会产生明显不同的磁化方向。