Why is the far side of the Moon so different from the side we see?

In one line

The rule

The near side of the Moon (the side facing Earth) and the far side (the side facing away) have different surfaces because of differences in their crust, history of impacts, and how the Moon is locked to Earth by gravity.

Let's understand it simply

Imagine you are rolling a roti. One side gets more heat from the tawa, the other less. Over time, the two sides look and feel different. The Moon is like that. The side always facing us (the near side) has big dark patches called maria (flat lava plains). The far side has almost none—it's full of craters (holes from impacts) and mountains. Why? The Moon always shows us the same face because it spins once for every trip around Earth. So, one side always faces Earth, and the other always faces away.

How it works

1. Tidal locking: Long ago, Earth’s gravity slowed the Moon’s spin until it always shows us the same side. This is called tidal locking.
2. Crust thickness: The Moon’s near side has a thinner crust (outer layer) than the far side.
3. Volcanoes and lava: After the Moon formed, huge space rocks hit it. On the near side, lava could break through the thin crust, filling in craters and making smooth, dark maria.
4. Far side stays rough: The far side’s crust is thicker, so lava could not break through easily. Craters stayed, and few maria formed.
5. Impacts: Both sides got hit by asteroids, but the near side’s lava covered up many old craters.
6. Earth’s gravity: The near side is pulled a bit more by Earth, which may have helped keep its crust thinner.

The story behind it

Scientists think the Moon formed about 4.5 billion years ago when a Mars-sized object hit Earth. The debris came together to make the Moon. Over time, the Moon cooled. Earth’s gravity slowed the Moon’s spin until it became tidally locked. In the 1950s and 1960s, Soviet Luna missions and then Apollo missions sent back the first photos of the far side. People were shocked: it looked nothing like the side we see from Earth.

Where you see it in real life

• Full Moon: The side you see during a full moon is always the same—the near side, with big dark patches (maria).
• Photos from space: Pictures from satellites show the far side is full of craters, with almost no maria.
• Maps of the Moon: Lunar maps show the near side has about 31% maria; the far side has only 1%.
• Apollo missions: Astronauts orbited the Moon and saw the far side for the first time.
• Radio signals: The far side is called the “dark side” not because it is dark, but because it is hidden from Earth’s view and radio signals.
• Chandrayaan-2: India’s mission sent back images of the far side, showing its rough, cratered surface.

Why it matters

• Moon landings: Knowing the surface helps space agencies choose safe landing spots.
• Learning about Earth: Studying the Moon’s history helps us understand how Earth and the solar system formed.
• Radio astronomy: The far side is quiet—no radio signals from Earth—so it’s a good place for space telescopes.
• Future missions: Scientists plan to build bases or telescopes on the far side.

Worked example

Let’s compare the maria (lava plains) on both sides:

Given: Near side maria = 31% of surface, Far side maria = 1%
Step 1: Find the difference in maria coverage
Step 2: 31% (near side) - 1% (far side) = 30%
Step 3: The near side has 30% more maria than the far side

Common mistakes

• Thinking the far side is always dark: It gets sunlight too, just not visible from Earth.
• Believing both sides look the same: The far side is much rougher and has more craters.
• Saying we never see the far side: We can see it with spacecraft, just not from Earth.
• Mixing up maria and craters: Maria are flat, dark lava plains; craters are round holes from impacts.

Remember it

The near side of the Moon is smooth and dark in places because lava filled its craters; the far side is rough and full of holes because its crust is thicker and lava could not flow.