Earth has been hit by even more impacts than Mars has but because Earth has a thick atmosphere and strong weather systems the impact craters get weathered down until they are no longer visible or the the objects burn up in the atmosphere before hitting the ground.
Extreme_Track1n t1_j97in53 wrote
Reply to comment by Itis_TheStranger in This image of Mars shows the north polar ice cap, the border between highlands and lowlands, former river valleys, plains covered by dark sands and the large Hellas Planitia impact basin in the south. Credit: ESA/DLR/FU Berlin by MistWeaver80
Earth has been hit by even more impacts than Mars has but because Earth has a thick atmosphere and strong weather systems the impact craters get weathered down until they are no longer visible or the the objects burn up in the atmosphere before hitting the ground.