NASA (large moon); NASA/GSFC (LNO); Shutterstock.com (background)

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Blast Off!

The moon formed billions of years ago, but scientists are still learning more about it.

April 28, 2025
By Nicole Tocco

As You Read, Think About: Would you want to visit the moon? 

The Grand Canyon is one of the most amazing landmarks on Earth. It was carved out over millions of years by the Colorado River and other bodies of water. Did you know that the moon has canyons too? Two of them, Vallis Schrödinger and Vallis Planck, are located near the moon’s south pole. They’re deeper than the Grand Canyon—but were created in less than 10 minutes! An asteroid, or giant space rock, crashed into the moon 3.8 billion years ago. The crash sent giant rocks raining down on the lunar surface. That left the two giant canyons behind.

The moon was formed by another rocky collision, about 4.5 billion years ago. An early version of Earth was hit by smaller object called Theia. Dust and molten rock from the crash sprayed out into space and formed the moon.

Scientists used photos from NASA’s Lunar Reconnaissance Orbiter to figure out how the two canyons formed. They released their findings in February. Researchers are studying the area because it’s set to be the location of the next mission to the moon. Read on to learn more about Earth’s closest neighbor in space.

Collision Course

Shutterstock.com 

The moon is covered with craters. These large holes on the lunar surface are formed by space rocks. Earth’s atmosphere burns or breaks up most meteoroids and other space rocks before they reach the planet’s surface. But the moon’s atmosphere is very weak and thin. It does not protect the lunar surface from being struck by objects flying through space.

Mapping the Moon

Shutterstock.com 

NASA's Lunar Reconnaissance Orbiter

From 1969 to 1972, 12 American astronauts landed on the moon. No one has been back since. But spacecraft like the Lunar Reconnaissance Orbiter (right) help scientists continue to study the moon. Since 2009, the orbiter has been mapping the moon to help guide future missions.

What can visitors expect? Nearly everything is gray, and most rocks are very sharp. There is no wind or rain, so footprints left by astronauts more than 50 years ago remain. And since there is no air to carry sound waves, there is no sound on the moon.

Waterless Seas

NASA/ullstein bild via Getty Images (moon landing); Heritage Space/Heritage Images via Getty Images (footprint)

Buzz Aldrin walks on the moon; A footprint left in 1969 (inset)

Early astronomers believed the dark spots on the moon were bodies of water. These areas were given the name mare (MAHR-ay), or “sea.” We now know that they were blasted out by asteroid strikes more than 3 billion years ago. They were later filled with lava that eventually froze.

In 1969, NASA’s Apollo 11 spacecraft landed at the edge of one of these areas, the Sea of Tranquility. It marked the first time astronauts, including Buzz Aldrin (right), walked on the moon.

The Far Side

Here on Earth, we only ever see one side of the moon—the near side. The first images of the far side of the moon were taken in 1959 by a spacecraft called Luna 3. The far side of the moon (below) has even more craters than the near side but has fewer dark seas.

NASA/GSFC/Arizona State University

The far side of the moon

  1. Why does the article mention the Grand Canyon?
  2. How has scientists’ understanding of the moon’s dark spots changed over time?
  3. How has the Lunar Reconnaissance Orbiter helped scientists learn about the moon?
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