Williams J-P, Pathare A V, Costello E S, Gallinger C L, Hayne P O, Ghent R R, Paige D A, Siegler M A, Russell P S, Elder C M
Earth, Planetary and Space Sciences University of California Los Angeles CA USA.
Planetary Science Institute Tucson AZ USA.
J Geophys Res Planets. 2022 May;127(5):e2021JE007131. doi: 10.1029/2021JE007131. Epub 2022 Apr 27.
The distribution of impact craters on the ejecta of Giordano Bruno, a recent (<10 Ma) 22-km diameter crater within the lunar highlands, exhibits substantial variations. We surveyed craters ≥ 10 m across a 1,323 km area of Giordano Bruno's ejecta and compared the distribution of craters with variations in thermophysical properties derived from the Lunar Reconnaissance Orbiter Diviner instrument. We used Diviner-derived rock abundance and nighttime regolith temperatures along with thermal model-predicted surface temperatures for a diversity of terrains to identify and isolate areas of the ejecta based on thermophysical properties such as bulk density and thermal conductivity. We found that thermophysical properties of the ejecta vary considerably both laterally and vertically, and consistently differ from typical regolith, indicating the presence of higher thermal inertia materials. Crater-size frequencies are significantly lower in areas with terrain properties exhibiting higher: rock abundance, nighttime temperatures, and/or modeled thermal inertia. This discrepancy in crater distribution increases for craters smaller than ∼25 m. These thermophysical variations indicate changes in the mechanical properties of the target materials. We suggest that these variations-specifically, terrain-dependent crater scaling variations and impactor-scale heterogeneities in material properties such as the presence or absence of large boulders-may influence crater diameters or inhibit crater production altogether in Giordano Bruno's ejecta; furthermore, these factors are size-dependent.
在月球高地中，最近形成（<10 Ma）的直径22公里的乔达诺·布鲁诺撞击坑的喷出物上，撞击坑的分布呈现出显著变化。我们在乔达诺·布鲁诺喷出物的1323平方公里区域内，对直径≥10米的撞击坑进行了调查，并将撞击坑的分布与由月球勘测轨道飞行器Diviner仪器得出的热物理性质变化进行了比较。我们使用Diviner得出的岩石丰度和夜间风化层温度，以及热模型预测的多种地形的表面温度，根据诸如堆积密度和热导率等热物理性质来识别和划分喷出物区域。我们发现，喷出物的热物理性质在横向和垂直方向上都有很大变化，并且始终与典型的风化层不同，这表明存在具有较高热惯性的物质。在岩石丰度、夜间温度和/或模拟热惯性较高的地形区域，撞击坑尺寸频率显著较低。对于小于约25米的撞击坑，这种撞击坑分布的差异会增大。这些热物理变化表明目标物质的力学性质发生了改变。我们认为，这些变化——具体来说，与地形相关的撞击坑缩放变化以及物质性质（如大石块的存在与否）中撞击体尺度的不均匀性——可能会影响乔达诺·布鲁诺喷出物中的撞击坑直径，或者完全抑制撞击坑的形成；此外，这些因素还与尺寸有关。
