Expert: Ed - 3/24/2008

Question
why do some areas of the moon reflect more light than others? ie, why are there dark patches, what is different about their physical nature than the more reflective areas?

thank you

Answer
Feiv,

The dark areas are called maria.  They are made of basalt, which is a relatively darker kind of rock.  Basalt is volcanic.  The dark, basaltic areas were formed after HUGE asteroid or comet impacts ripped apart the surface of the moon, (usually millions or billions of years ago).  After the asteroid impact, hot magma from the interior of the moon poured into the crater, and left the dark basalt that we see today.

The lighter areas tend to be mountains, also called highlands or terrae.  They are leftover from the rims of old craters, formed by the same impacts described above.

Look at this NASA webpage:
http://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level2/moon.html

I hope this is helpful.  Keep Looking Up!
--Ed