环境地球化学国家重点实验室知识库

In this paper, we present a global database of craters larger than 0.7 km in diameter on the surface of (4) Vesta, which we created based on a global mosaic of the Dawn spacecraft's high-altitude mapping orbit (HAMO) images at a resolution of similar to 60 m/pixel and cross-checked using the images from the low altitude mapping orbit (LAMO) mission phase. The method to produce the crater database consists of visual crater identification and mathematical shape determination. To give precise measurements, topographic corrections have also been considered by combining the digital elevation model (DEM) data in this global survey. We calculated the morphometric parameters of the craters, which consist of diameter, depth, depth-to-diameter ratio, ellipticity, and azimuth of the major axis. Our results show that the craters on (4) Vesta are very shallow, with a mean depth-to-diameter ratio of similar to 0.065, which is similar to that of the craters on (1) Ceres and (25143) Itokawa but lower than for craters on other solid bodies. The results also show that the fractions of craters with an ellipticity greater than 1.1 or 1.2 are smaller than those of craters on the Martian surface, which is probably because few secondaries exist on the surface of (4) Vesta. In addition, the azimuths of the major axis are almost uniformly distributed in different directions. Our globally consistent crater database has many potential applications for future studies such as geologic mapping and surface age dating.