Network of thermal cracks in meteorites due to temperature variations: new experimental evidence and implications for asteroid surfaces
Network of thermal cracks in meteorites due to temperature variations: new experimental evidence and implications for asteroid surfaces
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由于温度变化而导致的陨石热裂纹网络：新的实验证据及其对小行星表面的影响
DOI：
10.1093/mnras/staa3183
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发表时间：
2020
影响因子：
4.8
通讯作者：
P. Michel
中科院分区：
文献类型：
--
作者：
G. Libourel;C. Ganino;M. Delbo’;M. Niezgoda;B. Remy;L. Aranda;P. Michel
近年来，一些研究表明，由于地球和火星上的温度变化，岩石热破裂的重要性。岩石热裂解也可能是月球表面的一个过程。这些温度变化以及变化率在没有大气层的天体上可以达到很大的幅度，特别是在那些达到近日点距离的天体上，如近地小行星。另一方面，这些机构的裂纹的形成，几何形状和扩展尚未得到充分的研究。在这里，我们展示了球粒陨石的热裂解实验室实验的结果，这些球粒陨石在经受快速温度循环时会形成裂缝网络，其幅度与近日点距离较低的小行星所经历的幅度相似。在数百次温度循环中，裂纹的深度可以达到几百微米，与理论研究一致。我们发现含水矿物的脱水促进了裂化过程。裂纹网络的形成增加了试样表面和次表面的孔隙率。我们认为，这一过程可以帮助解释最近发现的小行星Ryugu和Bennu上大多数巨石的非常多孔的表面。
In recent years, several studies have shown the importance of thermal fracturing of rocks due to temperature variations, on The Earth and Mars. Rock thermal cracking might also be a process at play on the lunar surface. These temperature variations as well as change rates can reach important amplitude on bodies without an atmosphere, in particular on those that reach small perihelion distances such as near-Earth asteroids. On the other hand, the formation, geometry, and extension of cracks on these bodies have not been fully investigated yet. Here, we show results of thermal cracking laboratory experiments on chondrite meteorites, which develop networks of cracks when subjected to rapid temperature cycles with amplitudes similar to those experienced by asteroids with low perihelion distances. The depth of the cracks can reach a few hundred of microns in some hundreds of temperature cycles, in agreement with theoretical studies. We find that dehydration of hydrous minerals enhances the cracking process. The formation of crack networks increases the porosity both at the surface and in the sub-surface of our specimens. We propose that this process could help explaining the recent finding of the very highly porous surfaces of most of the boulders on the asteroids Ryugu and Bennu.