Borealis Planitia is a large plain on Mercury with a smooth floor, thought to be similar to a lunar mare.Topographic Features and Surface History, Atlas of Mercury (NASA SP-423), 1976 It is centered at 73.4° N, 79.5° W. The name is Latin for Northern Plain.
Borealis Planitia was formed by volcanic activity around 3.7 billion years ago and is the largest region of smooth plains on the planet.
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