Mercury’s volcanic history could help scientists figure out where to look for Earth-like worlds. Mercury ceased volcanic activity 3.5 billion years ago while the moon ceased volcanic activity 2.5-3.0 billion years ago. Both Mercury and the moon are covered by one big plate, unlike the Earth, which is covered by multiple plates. As Mercury and the moon aged and cooled, their plates contracted, preventing lava from oozing out. 

Earth in contrast, which is roughly the same age as Mercury, is still volcanically active. The reason is because earth is bigger and isn’t covered by one big plate. By understanding these patterns of volcanic activity, astronomers can search for earth-like planets by either targeting young planetary systems or looking at the bigger planets in older systems. Pretty cool!