The target bodies of C‐complex asteroid sample return missions are carbonaceous chondrite‐like near‐Earth asteroids (NEAs), chosen for the abundance and scientific importance of their organic compounds and “hydrous” (including hydroxylated) minerals, such as serpentine‐group phyllosilicates. Science objectives include returning samples of pristine carbonaceous regolith from asteroids for study of the nature, history, and distribution of its constituent minerals, organic material, and other volatiles. Heating after the natural aqueous alteration that formed the abundant phyllosilicates in CM and similar carbonaceous chondrites dehydroxylated them and altered or decomposed other volumetrically minor constituents (e.g., carbonates, sulfides, organic molecules; Tonui et al. 2003, 2014). We propose a peak‐temperature thermometer based on dehydroxylation as measured by analytical totals from electron probe microanalysis (EPMA) of matrices in a number of heated and aqueously altered (but not further heated) CM chondrites. Some CM lithologies in Maribo and Sutter’s Mill do not exhibit the matrix dehydroxylation expected for surface temperatures expected from insolation of meteoroids with their known orbital perihelia. This suggests that insolated‐heated meteoroid surfaces were lost by ablation during passage through Earth’s atmosphere, and that insolation‐heated material is more likely to be encountered among returned asteroid regolith samples than in meteorites. More generally, several published lines of evidence suggest that episodic heating of some CM material, most likely by impacts, continued intermittently and locally up to billions of years after assembly and early heating of ancestral CM chondrite bodies. Mission spectroscopic measures of hydration can be used to estimate the extent of dehydroxylation, and the new dehydroxylation thermometer can be used directly to select fragments of returned samples most likely to contain less thermally altered inventories of primitive organic molecules.

中文翻译：

---

CM球粒陨石的热变质作用：基于脱羟基作用的峰值温度温度计及其对小行星Ryugu和Bennu样品返回的影响

C复杂小行星样本返回任务的目标物体是碳质球粒陨石状近地小行星（NEA），其选择是出于其有机化合物和“含水”（包括羟基化）矿物（例如蛇纹石族）的丰度和科学重要性。页硅酸盐。科学目标包括从小行星返回原始碳质硬质岩样品，以研究其组成矿物，有机物质和其他挥发物的性质，历史和分布。天然水蚀后，在CM中形成大量的层状硅酸盐和类似碳质球粒陨石后加热，使它们脱羟基，并改变或分解了其他体积较小的成分（例如碳酸盐，硫化物，有机分子； Tonui等人，2003年，2014年）。我们提出了一种基于脱羟基的峰值温度温度计，该温度计是通过对许多加热的和经水改变（但不进一步加热）的CM球粒晶体的基质的电子探针微分析（EPMA）进行分析而得出的。Maribo和Sutter's Mill的某些CM岩性未显示出因流星体因其已知的轨道近日膜层日晒而预期的表面温度所预期的基质脱羟基作用。这表明，在流经地球大气层时，消融损失了孤立加热的流星体表面，比起陨石，在返回的小行星碎屑岩样品中更容易遇到孤立加热的物质。更普遍地，几条已公开的证据表明，某些CM材料的间歇加热，很可能是由于撞击而引起的，在祖先CM球粒陨石体的组装和早期加热之后，数十亿年间断续续和局部地持续进行。可以使用水合的任务光谱学方法估算脱羟基的程度，并且可以将新的脱羟基温度计直接用于选择最有可能包含较少热变化的原始有机分子清单的返回样品的片段。