Grazing impacts on Mars: A record of lost satellites
Grazing impacts on Mars: A record of lost satellites
复制标题
放牧对火星的影响：丢失卫星的记录
DOI：
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发表时间：
1982
期刊：
影响因子：
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通讯作者：
A. B. Lutz
中科院分区：
文献类型：
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作者：
P. Schultz;A. B. Lutz
可以根据所形成的弹坑的细长形状和喷出物沉积的独特模式来确定掠射撞击。在火星上有超过170个大于3公里的撞击坑，占脊状平原陨石坑总数的5%以上。相比之下，月球在月海上只有一个大于3公里的可比较的例子，这一频率与各向同性撞击物涌入的理论估计一致。许多火星食草动物似乎出现在沿着大圆圈。最近的例子一般影响在东西方向，而老食草动物影响在更北的方向。我们解释了过多的食草动物和共同的影响方向的卫星，其轨道随时间的潮汐衰减的结果。如果所有的轨道最初都有类似火卫一和火卫二以及最近的食草动物轨道的小倾角，那么撞击方向随时间的变化可以解释为由于火星惯性矩的变化而导致地壳移动的结果。火星表面轨道轴（轨道极点）的投影位置表明，火星的地理极点最初更多地位于低纬度地区。这些卫星所代表的质量中，超过95%的质量在月球平原的火山平原就位之前就已经撞击。据估计，掠食撞击物的总质量将形成一颗直径至少为225公里的卫星。这些结果可能会为火卫一和火卫二的起源提供新的线索，也许火星的角动量。«少
Grazing impacts can be identified on the basis of the elongate shape of the resulting crater and a distinctive pattern of ejecta deposits. Over 170 such impact craters larger than 3 km are recognized on Mars, and they represent more than 5% of the total crater population of the ridged plains. In contrast, the moon exhibits only one comparable example larger than 3 km on the maria, a frequency consistent with theoretical estimates for an isotropic influx of impactors. Many Mars grazers appear to occur along great circles. The most recent examples generally impacted in an east-west direction, whereas older grazers impacted in more northerly directions. We interpret the excessive number of grazers and the common impact directions as the result of satellites whose orbits tidally decayed with time. If all orbits originally had small inclinations similar to the orbits of Phobos and Deimos as well as the most recent grazers, then the change in impact direction with time can be explained as the result of shifts in the crust due to changes in the martian moments of inertia. The locations of the projected orbital axes (orbit-pole points) on the martian surface indicate that the geographic poles of Mars originallymore » were situated at lower latitudes. More than 95% of the mass represented by these proposed satellites impacted prior to the emplacement of the volcanic plains of Lunae Planum. The estimated combined mass of grazing impactors would form a satellite at least 225 km in diameter. These results may provide new clues for the origin of Phobos and Deimos and perhaps the angular momentum of Mars.« less