安提俄珀90号上的巨型陨石坑？
A Giant Crater on 90 Antiope?
摘要：
在2007-2008年期间，对90 Antiope的两个组成部分进行了相互事件观测。在J2000黄道坐标系中，极点位置被精确到β 0 = 199.5+/-0.5 eg和β 0 = 39.8+/-5 deg，保持组件的物理解决方案不变，同化为两个完美的罗氏椭圆体，并在2005年共同事件季节之后导出（Descamps等人，2007年）。此外，在其中一个组件上引入了一个大规模的地质凹陷，以更好地匹配观测到的光变曲线。这个直径约68公里的巨大地质特征，可以假设为碗状的撞击坑，确实是光变曲线“肩膀”上所见的光度不对称的原因。然后将堆积密度重新计算为1.28+/-0.04 gcm-3，以考虑这种大尺度的非凸性。这个巨大的陨石坑可能是一个100公里大小的原始安提俄珀与另一个忒弥斯家族成员巨大碰撞的后果。这一说法得到了以下事实的支持，即安提俄佩的孔隙率（约50%）足以在这样的撞击中幸存下来而不会被完全摧毁。这一猛烈的冲击将产生足够的角动量，使原安提俄珀分裂成两个等大小的物体。我们计算得出，撞击物的直径必须大于~17公里，撞击速度在1至4公里/秒之间。有了这样一个抛射体，这个事件有50%的可能性发生在忒弥斯家族的时代。
英文摘要：
Mutual event observations between the two components of 90 Antiope were carried out in 2007-2008. The pole position was refined to lambda0 = 199.5+/-0.5 eg and beta0 = 39.8+/-5 deg in J2000 ecliptic coordinates, leaving intact the physical solution for the components, assimilated to two perfect Roche ellipsoids, and derived after the 2005 mutual event season (Descamps et al., 2007). Furthermore, a large-scale geological depression, located on one of the components, was introduced to better match the observed lightcurves. This vast geological feature of about 68 km in diameter, which could be postulated as a bowl-shaped impact crater, is indeed responsible of the photometric asymmetries seen on the "shoulders" of the lightcurves. The bulk density was then recomputed to 1.28+/-0.04 gcm-3 to take into account this large-scale non-convexity. This giant crater could be the aftermath of a tremendous collision of a 100-km sized proto-Antiope with another Themis family member. This statement is supported by the fact that Antiope is sufficiently porous (~50%) to survive such an impact without being wholly destroyed. This violent shock would have then imparted enough angular momentum for fissioning of proto-Antiope into two equisized bodies. We calculated that the impactor must have a diameter greater than ~17 km, for an impact velocity ranging between 1 and 4 km/s. With such a projectile, this event has a substantial 50% probability to have occurred over the age of the Themis family.
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