Measurements of the low‐temperature thermodynamic and physical properties of meteorites provide fundamental data for the study and understanding of asteroids and other small bodies. Of particular interest are the CM carbonaceous chondrites, which represent a class of primitive meteorites that record substantial chemical information concerning the evolution of volatile‐rich materials in the early solar system. Most CM chondrites are petrographic type 2 and contain anhydrous minerals such as olivine and pyroxene, along with abundant hydrous phyllosilicates contained in the meteorite matrix interspersed between the chondrules. Using a Quantum Design Physical Property Measurement System, we have measured the thermal conductivity, heat capacity, and thermal expansion of five CM2 carbonaceous chondrites (Murchison, Murray, Cold Bokkeveld, Northwest Africa 7309, Jbilet Winselwan) at low temperatures (5–300 K) which span the range of possible surface temperatures in the asteroid belt and outer solar system. The thermal expansion measurements show a substantial and unexpected decrease in CM2 volume as temperature increases from 210 to 240 K followed by a rapid increase in CM2 volume as temperature rises from 240 to 300 K. This transition has not been seen in anhydrous CV or CO carbonaceous chondrites. Thermal diffusivity and thermal inertia as a function of temperature are calculated from measurements of density, thermal conductivity, and heat capacity. Our thermal diffusivity results compare well with previous estimates for similar meteorites, where conductivity was derived from diffusivity measurements and modeled heat capacities; our new values are of higher precision and cover a wider range of temperatures.

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CM碳质球粒陨石的惊人热学性质

陨石的低温热力学和物理性质的测量为研究和理解小行星和其他小物体提供了基础数据。特别令人关注的是CM碳质球粒陨石，它代表一类原始的陨石，记录了有关早期太阳系中易挥发物质的演变的大量化学信息。大多数CM球粒陨石是岩石学类型2，含有无水矿物，例如橄榄石和辉石，以及散布在各球粒之间的陨石基质中所含的大量含水层状硅酸盐。使用Quantum Design物理性质测量系统，我们测量了5种CM2碳质球粒陨石（Murchison，Murray，Cold Bokkeveld，西北非洲7309，吉比勒特·温瑟尔旺（Jbilet Winselwan）处于低温（5-300 K）范围内，该温度跨过小行星带和外部太阳系的可能表面温度范围。热膨胀测量结果表明，随着温度从210 K升高到240 K，CM2体积显着且出乎意料的减少，随后随着温度从240 K升高至300 K，CM2体积迅速增加。在无水CV或CO碳质中未发现这种转变球粒陨石。热扩散率和热惯性随温度的变化是通过测量密度，导热率和热容量来计算的。我们的热扩散率结果与以前对类似陨石的估计值比较，后者的电导率来自扩散率测量值和模拟的热容；