The James Webb Space Telescope can potentially explore the geological diversity of the surfaces of rocky exoplanets, especially due to its access to mid-infrared wavelengths. Here we investigate the level of geological detail that it could be possible to observe with the low-resolution spectroscopy and photometric modes of the mid-infrared instrument onboard the James Webb Space Telescope. We used new emissivity measurements of 15 basaltic samples between 2 μm and 25 μm to produce synthetic spectra and photometric fluxes. We found that the mid-infrared instrument can, in principle, distinguish several specific mineralogical and bulk chemical signals among relatively similar rocks. In particular, hydrous minerals, such as amphibole and serpentine, which would signal the existence of past or present water, can have observable characteristics in both low-resolution spectroscopy observations (with the precision of 5 eclipses) and the integrated fluxes over mid-infrared instrument filter bandwidths (20–100 eclipses). Photometric fluxes are also sensitive to bulk compositions (for example, wt% Al₂O₃), which reflect magmatic processes. Our work demonstrates the potential for the James Webb Space Telescope and future observatories to access a fuller picture of exoplanet surface geology.

詹姆斯韦伯太空望远镜有可能探索岩石系外行星表面的地质多样性，特别是由于它可以获得中红外波长。在这里，我们研究了使用詹姆斯韦伯太空望远镜上的中红外仪器的低分辨率光谱和光度模式可以观察到的地质细节水平。我们对 15 个 2 μm 至 25 μm 之间的玄武岩样品进行了新的发射率测量，以生成合成光谱和光度通量。我们发现，中红外仪器原则上可以在相对相似的岩石中区分几种特定的矿物学和体化学信号。特别是含水矿物，如闪石和蛇纹石，它们会预示着过去或现在的水的存在，在低分辨率光谱观测（精度为 5 次日食）和中红外仪器滤光片带宽（20-100 次日食）上的积分通量中都可以具有可观测的特性。光度通量对反映岩浆过程的块状成分（例如，wt% Al₂O₃）也很敏感。我们的工作展示了詹姆斯韦伯太空望远镜和未来天文台更全面地了解系外行星表面地质的潜力。