Maria (singular: mare) are the dark, smooth plains that cover a significant portion of the lunar surface. The word "mare" is Latin for "sea," a name given by early astronomers who mistook these features for bodies of water.
Here's how they differ from other lunar surface formations:
1. Composition:
* Maria: Composed primarily of basalt, a dark, volcanic rock. This is in contrast to the lighter-colored highlands, which are composed of anorthosite, another type of igneous rock.
* Highlands: Consist mostly of anorthosite, a light-colored, crystalline rock.
2. Age:
* Maria: Formed relatively early in the Moon's history, between 3.9 and 3.0 billion years ago.
* Highlands: Generally much older, dating back to the early formation of the Moon around 4.5 billion years ago.
3. Formation:
* Maria: Formed by massive volcanic eruptions that spewed lava across the lunar surface, filling in impact craters and creating vast plains.
* Highlands: Formed by the intense bombardment of meteoroids and asteroids during the early Solar System.
4. Topography:
* Maria: Relatively smooth and flat, with only subtle undulations.
* Highlands: Highly cratered, rugged, and mountainous, with towering peaks and deep valleys.
5. Other features:
* Maria: Often contain features called "rilles," which are long, narrow depressions that were likely formed by volcanic activity or flowing lava.
* Highlands: Contain numerous impact craters, ranging in size from small, bowl-shaped depressions to vast, multi-ring basins.
In essence, Maria are vast, dark plains formed by ancient volcanic eruptions, while the highlands are older, heavily cratered areas formed by intense bombardment. The distinct composition and age of these two features provide valuable insights into the Moon's geological history.
