Cratering rates on the Galilean satellites.
Cratering rates on the Galilean satellites.
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DOI：
10.1006/icar.1998.6015
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发表时间：
1998-12
期刊：
影响因子：
3.2
通讯作者：
K. Zahnle;L. Dones;H. Levison
中科院分区：
文献类型：
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作者：
K. Zahnle;L. Dones;H. Levison
我们利用最新的理论进展对彗星和小行星的起源和轨道演化，以获得在木星系统的陨石坑率的修订估计。我们发现，大多数，可能超过90%，伽利略卫星上的陨石坑是由彗星族彗星（JFC）的影响造成的。这些彗星的周期很短，通常在低倾角的轨道上，其动力学由木星主导。近各向同性彗星（长周期和哈雷型）的贡献在1-10%的水平。特洛伊小行星也可能在1-10%的水平上很重要;如果它们很重要，它们对较小的陨石坑尤其重要。主带小行星目前并不重要，因为木卫三上每形成一个20公里的陨石坑，就意味着一个直径200公里的母小行星被破坏，这种破坏速度远远超过今天小行星带的资源。直径20公里的陨石坑是由更大的撞击物造成的;这样的事件在伽利略卫星上大约一百万年才发生一次。木卫二上20公里长的陨石坑很少，这表明它的表面大约有10 Ma。木卫三表面轻微的陨石坑一般为0.5-1.0 Ga。这些估计的不确定性约为5倍。木卫四很老了，可能超过4Ga。它的坑太多，无法用JFC的电流来解释。木卫三上没有明显的顶点-前顶点不对称性可能与陨石坑平衡相一致，但它更容易被理解为冰壳非同步旋转的证据。
We exploit recent theoretical advances toward the origin and orbital evolution of comets and asteroids to obtain revised estimates for cratering rates in the jovian system. We find that most, probably more than 90%, of the craters on the Galilean satellites are caused by the impact of Jupiter-family comets (JFCs). These are comets with short periods, in generally low-inclination orbits, whose dynamics are dominated by Jupiter. Nearly isotropic comets (long period and Halley-type) contribute at the 1-10% level. Trojan asteroids might also be important at the 1-10% level; if they are important, they would be especially important for smaller craters. Main belt asteroids are currently unimportant, as each 20-km crater made on Ganymede implies the disruption of a 200-km diameter parental asteroid, a destruction rate far beyond the resources of today's asteroid belt. Twenty-kilometer diameter craters are made by kilometer-size impactors; such events occur on a Galilean satellite about once in a million years. The paucity of 20-km craters on Europa indicates that its surface is of order 10 Ma. Lightly cratered surfaces on Ganymede are nominally of order 0.5-1.0 Ga. The uncertainty in these estimates is about a factor of five. Callisto is old, probably more than 4 Ga. It is too heavily cratered to be accounted for by the current flux of JFCs. The lack of pronounced apex-antapex asymmetries on Ganymede may be compatible with crater equilibrium, but it is more easily understood as evidence for nonsynchronous rotation of an icy carapace.