关于这张图
This image from NASA's Mars Reconnaissance Orbiter (MRO) shows two small impact craters located in Meridiani Planum. This is an example of the geologic principle of superposition: figuring out what happened first by looking at how features interact with each other. We can see that one of the craters must have hit the surface after the other was already there, but which came first? We can see that the ejecta blankets look rougher on the right side of the image than they do on the left. This could mean that the right side ejecta is newer, and has not been exposed to the wind as much as the left…
