Observe the Moon

WHAT CAN YOU SEE WITH YOUR EYES?

The first thing you might notice on the Moon is the dark and light patches. Those colors show you the different types of rock that tell the story of what happened to the Moon.

Close-up image of smooth basins and sharp craters in the Mare Nectaris region, taken by the Lunar Reconnaissance Orbiter. Credit: NASA

Maria

The darker areas are basins that flooded with lava after big space rocks crashed into the Moon’s crust billions of years ago. These dark patches are called “maria,” which means “seas,” because people thought they looked like oceans. They don’t actually contain liquid water.

Highlands

The lighter places are called highlands, taller areas that are a lot like continents on Earth. Highlands have many round craters pressed into their surface from millions of impacts by space rocks.

WHAT CAN YOU SEE WITH BINOCULARS?

With your binoculars, look at the lightest patch near the bottom of the Moon. You might see a white circle with a grey rim and bright streaks that spread out in many directions.

That is a huge crater, slightly bigger than Rhode Island, called the Tycho crater. It formed when a large space rock hit the Moon about 100 million years ago. The bright lines are rays of dust that blasted outward when the space rock hit. The lines stretch as far as the distance from San Francisco to Salt Lake City!

WHAT CAN YOU SEE WITH A TELESCOPE?

As you get more familiar observing the Moon, look for differences in texture between the dark maria and the bright highlands.

You may notice that the maria can appear smoother, while the highlands have more craters. That’s because the maria are younger than the surrounding highlands. Lava flows in the maria also helped cover up the craters that were already there.

When you look at rocky planets or moons, the older surfaces will show more craters because they have had a longer time to be hit by space rocks.

WHAT YOU SEE WILL CHANGE

The number of features visible on the Moon will depend on the angle of the Sun, which changes with the Moon’s phases.

When the Moon is a crescent or half full, the Sun is at a low angle and casts shadows that help outline things like craters.

When the Moon is close to full, there are few shadows so it is harder to see the high and low points of the craters.

The best way to look for textures and details on the Moon is to point your telescope to the shadow line, where the Moon goes from light to dark.

These two images are of the same crater under different lighting. On the left the Sun was lower on the horizon and on the right the Sun was high, approaching noon. Credit: NASA/GSFC/Arizona State University.

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