APOD 3.7

http://apod.nasa.gov/apod/ap110312.html

Above is the Mare Orientale, a lunar feature. It is also known as 'The Eastern Sea', though it is actually on the western edge now due to a change in our terminology. It formed around 3.8 billion years ago. Though it is difficult to see at most times from Earth, it will be visible temporarily later this month. Julius Heinreich Georg Franz discovered the feature. It is the youngest lunar basin, multiringed in character.  It is called a sea because astronomers once thought the basins might actually be seas.