An intensive study of impact craters to "probe" and "gauge" the complex geologic history of Mars and to further understand cratering as a formative process on terrestrial bodies

撞击坑是整个太阳系固体行星表面最普遍的地质过程；因此，它在行星地壳的早期形成、改造和某些情况下的含水蚀变中发挥了重要作用。越来越多的观测证据表明，撞击坑不仅在物理上改变了地球和火星的岩石表面，而且可能在早期生命的进化中发挥了重要作用，并促进了资源的集中。对撞击坑的研究可以用来阐明承载撞击坑的行星体复杂的地质历史。陨石坑通常在形态上是一致的，这使它们成为行星表面最容易识别的特征之一。因此，它们也是有用的天然“测量器”，对随时间变化的地质过程的影响敏感并记录下来。撞击坑按其一般形态和形态计量学分为简单、过渡和复杂，这已被确定为由陨石坑的大小、物体的重力和形成陨石坑的目标材料的强度控制。此外，陨石坑有效地挖掘、隆起并暴露出地下岩石，否则这些岩石可能不会通过其他过程暴露在地表（特别是在缺乏板块构造的火星上）。因此，充分暴露的陨石坑充当了行星体浅层到深层内部组成、地层和结构的天然“探测器”。拟议的研究计划侧重于识别和深入研究火星上保存最完好和暴露的陨石坑，并对覆盖它们的轨道可见、光谱、热物理和高程数据集进行分析、综合和解释。保存最完好的陨石坑提供了对陨石坑形成过程各个方面的最清晰的观察和见解；此外，它们将继续为研究火星上的侵蚀和沉积（即退化）提供基线。对暴露最好的复杂陨石坑的研究，重点是喷出物、陨石坑壁/阶地、中心结构等，将提供有关浅层到深层地下不同层次的成分、流变学/强度和结构的信息。拟议的研究将继续扩大我们对撞击过程的认识，以及它们作为一种自然“工具”的用途，以阐明已经并将继续对行星体起作用的其他过程。虽然这个研究项目的重点不是特别基于地面，但这里使用的数据和方法与勘探地质学、地球物理和环境遥感所使用的数据和方法相似，甚至包括用于国防的图像分析技术。因此，参与这项研究计划的HQP将学习直接适用于其他领域的基本技能。

Impact cratering is the most ubiquitous geologic process acting on solid planetary surfaces throughout the solar system; thereby, it played a significant role in the early formation, modification and in some cases the aqueous alteration of planetary crusts. Mounting observational evidence supports that impact cratering has not only physically modified the rocky surfaces of Earth and Mars but may have also played a significant role in the evolution of early life and facilitated the concentration of resources. The study of impact craters may be used to elucidate the complex geologic history of the planetary bodies that host them. Craters are generally consistent morphologically, making them one of the most easily recognized features on planetary surfaces. As such, they are also useful as natural "gauges" sensitive to and recording the effects of the geologic processes that modify them over time. Impact craters are classified by their general morphology and morphometry into simple, transitional, complex, which has been determined to be controlled by the size of the crater, gravity of the body and the strength of the target materials in which it formed. Furthermore, craters effectively excavate, uplift and expose subsurface rocks that may not otherwise be exposed at the surface by other processes (particularly on Mars where plate tectonics is lacking). Thereby, craters that are well-exposed act as natural "probes" of the composition, stratigraphy and structure of shallow to deep interiors of planetary bodies. The proposed research program focuses on the identification and intensive study of the best-preserved and -exposed craters on Mars and an analysis, synthesis and interpretation of orbital visible, spectral, thermophysical and elevation data sets covering them. The best-preserved impact craters provide the clearest observations and insights into various aspects of the cratering process; furthermore, they will continue to provide a baseline for studies of erosion and deposition (i.e., degradation) on Mars. A study of the best-exposed complex craters, focusing on ejecta, crater wall/terraces, central structures, etc., will provide information on the composition, rheology/strength and structure of various levels of the shallow to deep subsurface. The proposed research will continue to expand on our knowledge on the impact processes, and their usefulness as a natural "tool" for elucidating other processes that have and continue to act on planetary bodies. Although the emphasis of this research program is not specifically terrestrial-based, the data and methods employed here are similar to those utilized by exploration geology, geophysics, and environmental remote sensing, and even includes image analysis techniques used for national defense. As such, HQP involved in this research program will learn fundamental skills that are directly applicable to other fields.