Multiple exposure of moonrise over Lake Superior / Bob King
Tonight is full moon … or close enough. The actual moment of fullness happens tomorrow morning at 5:25. Most of us are familiar with the face of the "man in the moon" which we create from the dark and light patches on the moon’s face. These spots actually tell scientists much about the moon’s evolution.
The full moon through a small telescope – Bob King / News Tribune
The dark ones are called "maria" (MARR-ee-uh) after the Latin word for seas, which some ancient astronomers thought they resembled. They’re actually huge plains of dark basalt lava that bubbled up from the lunar crust and solidified some 3.5 billion years ago.
The lighter zones, called the lunar highlands, are the moon’s ancient crust that formed four billion years ago. They still contain a record of the rough and tumble days of the early solar sytem, when the moon and everything else was bombarded by countless asteroids and meteorites. Craters from that era pepper the highlands by the millions.
I want to draw your attention to one particular highland crater called Tycho, named after a famous 16th century astronomer. It’s 50 miles in diameter and so bright, that it’s easily visible with the naked eye on the lower edge of the moon. Look for a small, brilliant dot.
As craters go, Tycho is very young, only about 100 million years old. Compare that to most of the rest of the highland craters, with ages of several billion years. Due to the subtle bombardment of radiation from the sun and cosmic rays, the lunar surface darkens with time.
Tycho’s youth makes it bright and eye-catching especially around the time of full moon.