Maria and Terrae

2.3 - Be able to recognise the appearance of the principal naked-eye lunar surface formations (continued in 2.4)

2.4 - Understand the structure and origin of the principal naked-eye lunar surface formations, including:
b - maria
c - terrae

Mare (pronounced Mah-ree) is the Latin for sea. Maria is the plural, seas (porinounced Mah-ree-a).

These are dark areas on the Moon. Approximately 17% of the lunar surface is classed as maria. These were mistaken by early astronomers for seas and are also known as the lowlands..

Terrae is the collective name for highlands – bright areas that are higher on the Moon’s surface than maria. These are hilly, mountanous and brighter than maria.

Maria appear darker than the terrae as they contain more iron-rich elements. There are few maria on the far side of the moon.

Rocks brought back from the Apollo missions have shown they were formed 3-4 billion years ago.

There was a period called the ‘Heavy Bombardment’ when the Moon (and presumably the inner Solar System) underwent a time of frequent and violent impacts.

Millions of years (sometimes as many as 500 million years) later the Moon underwent a time of volcanic activity and lava was forced to the surface. This lava later turned to basalt. It flooded the lower impact areas and would have covered any other features on the landscape including other craters. The highlands were left untouched.

Today we can see a large number of craters on the Terrae and fewer on Maria which also implies they were formed at different times.

 

Interactive
Summary

Terra – brighter, more cratered

Maria – darker, less cratered

Questions
  • Why do scientists think that maria formed later than the highlands?
  • Explain how maria may have been formed.
Links

Serious Science Lunar Maria

Backyard Astro Copernicus and Montes Riphaeus

Maria map Map of maria