I'd say to help the reader quickly locate geographic regions.
True, maria are dark, smooth, <em>flat </em>surfaces on the moon.
hope this helps:)
They are considered to have originated from cyanobacteria through endosymbiosis—when a eukaryotic cell engulfed a photosynthesizing cyanobacterium that became a permanent resident in the cell
American black bear, Cougar, Big Horn Sheep and some others.
