Near-infrared (NIR) spectrometers on board current sample return missions Hayabusa2 and the Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer (OSIRIS-REx) from primitive bodies detected the presence of hydrated silicates on the surface of asteroids Ryugu and Bennu, respectively. These detections relied upon the study of the 2.7 μm OH-stretching spectral feature, whose peak position is related to the composition and structure of minerals. However, space weathering might alter the band profile, depth and position, thus complicating the interpretation of remote sensing data. In order to better understand these processes and provide support to space missions, we performed ion bombardment experiments on serpentine and saponite analogs. These two phyllosilicates are among the dominant mineral phases found in hydrated carbonaceous chondrites, which are possible analogs to surface materials observed on these primitive asteroids. We studied the behavior of the 2.7 μm band as a function of ion fluence and found that the evolution of the phyllosilicate depends on its nature. For the saponite sample, the band is only slightly affected by ion bombardment, while for both serpentine samples it shifts toward longer wavelengths. For both samples, peak intensity and width is not strongly affected. The band shift for serpentine indicates that space weathering introduces a bias in the interpretation of NIR remote sensing observations of phyllosilicates. The shift observed in our experiments can be detected by instruments on board Hayabusa2 and OSIRIS-REx, depending on the geometry of observation. Our findings provide support to the interpretation of such data.

当前样品返回任务Hayabusa2上的近红外（NIR）光谱仪和原始物体的起源-光谱解释-资源识别-安全性-Regolith Explorer（OSIRIS-REx）检测到小行星Ryugu和Bennu表面上存在水合硅酸盐， 分别。这些检测依赖于对2.7μm OH拉伸光谱特征，其峰值位置与矿物的组成和结构有关。但是，空间风化可能会改变波段分布，深度和位置，从而使遥感数据的解释复杂化。为了更好地理解这些过程并为太空任务提供支持，我们对蛇纹石和皂石类似物进行了离子轰击实验。这两种页硅酸盐是在水合碳质球粒陨石中发现的主要矿物相，这可能是在这些原始小行星上观察到的表面物质的类似物。我们研究了2.7μm谱带是离子通量的函数，发现页硅酸盐的演化取决于其性质。对于皂石样品，该条带仅受到离子轰击的轻微影响，而对于两个蛇形样品，其移向更长的波长。对于这两个样品，峰强度和峰宽均不受强烈影响。蛇纹石的带位移表明，空间风化对页硅酸盐的NIR遥感观测的解释产生了偏差。在我们的实验中观察到的偏移可以通过Hayabusa2和OSIRIS-REx上的仪器来检测，具体取决于观察的几何形状。我们的发现为此类数据的解释提供了支持。