Surface Properties and -Processes on Phobos from Spectrophotometric Data by HRSC (High Resolution Stereo Camera) on Mars Express

我们将对火卫一的光谱特性进行表征，以提高我们对火卫一表面结构和动态过程的理解，这些动态过程导致了在这颗火星卫星上观察到的明显的反照率和颜色模式。我们受益于火星快车上的HRSC(高分辨率立体相机)最新的窄带颜色和全色数据，这些数据是从广泛的照明相角和高空间分辨率获得的。HRSC的覆盖范围包括火卫一的后半球和远侧，其他目前在火星轨道上运行的航天器无法观测到这一点。目前已有超过327次火卫二的数据可用，预计还会有更多的数据。我们确定了圆盘分辨光度函数(S)，它将被用来绘制火卫一表面的光度特性图，并识别局部反照率异常，例如，表示表面粗糙度增加的区域。此外，我们使用来自HRSC颜色通道的数据在相机的高空间分辨率下绘制火卫一表面的多光谱属性。我们的测绘结果将与之前任务中的仪器数据进行比较，在这些任务中，火卫一著名的“红色”和“蓝色”光谱单位已经被识别出来。将从表面结构和动力学过程，如陨石坑喷发和空间风化等方面，讨论火卫一风化层和多光谱单元的特征。考虑到日本宇宙航空研究开发机构目前正在准备的火卫一样本送回任务MMX(火星月球探测器)，我们提出的项目是及时的。我们将对着陆点的选择和采样策略提出建议，以最大限度地实现这次即将到来的任务的科学回报。来自柏林理工大学和德国洛桑联邦储备银行行星研究所的团队在开展这项拟议的研究方面具有独特的经验。

We will characterize the spectrophotometric properties of Phobos to improve our understanding of the surface structure and the dynamic processes causing the distinct albedo and color patterns observed on this Martian satellite. We benefit from most recent narrow-band color and panchromatic data by HRSC (High-Resolution Stereo Camera) on Mars Express, obtained from a wide range of illumination phase angles and at high spatial resolution. The HRSC coverage includes Phobos’ trailing hemisphere and the farside, not observable by other currently Mars-orbiting spacecraft. Data from more than 327 Phobos flybys are available, and more data are expected to come. We determine disk-resolved photometric function(s), which will be used to map photometric properties of Phobos’ surface and to identify local albedo anomalies, representing e.g., areas of increased surface roughness. Furthermore, we use data from HRSC color channels to map multispectral properties of Phobos’ surface at the camera’s high spatial resolution. Results of our mapping will be compared with instrument data from previous missions, where Phobos’ well-known „red“ and „blue“ spectral units have been identified. The characteristics of Phobos’ regolith and the multispectral units will be discussed in terms of surface structure and dynamic processes, such as emplacement of crater ejecta and space weathering. Our proposed project is timely in the light of MMX (Martian Moon Explorer), JAXA’s sample return mission to Phobos, which is currently being prepared. We will make recommendations for choices of landing sites and sampling strategy to maximize the science return of this upcoming mission. The team from Technical University Berlin and the DLR Institute of Planetary Research is uniquely experienced to carry out this proposed study.