Final answer:
The scars on Mercury, known as long scarps, were likely caused by the planet shrinking and its crust compressing, resulting in these features forming after cratering events. Therefore the correct answer is compression of Mercury's crust
Step-by-step explanation:
The scars on Mercury were probably caused by the compression of Mercury's crust due to the planet shrinking, which resulted in the formation of long, curved cliffs known as scarps. These distinctive scarps can cut across craters, indicating that they had formed after the cratering events. This conclusion is supported by evidence that suggests Mercury's shrinkage occurred over the last 4 billion years and after the phase of heavy bombardment in the early solar system. Furthermore, the early solar system was chaotic, with many violent impacts that might have also contributed to Mercury's surface features, including massive collisions that potentially stripped away part of its mantle and crust.