What’s the Largest Crater on the Moon?

Written by Kirstin Harrington
Updated: January 27, 2023
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The sole natural satellite of Earth is the Moon. It has a diameter that is around one-fourth that of Earth. It is the biggest and most powerful satellite in relation to its parent planet, ranking sixth in the solar system

The Moon is bigger than any discovered dwarf planets of the solar system. It is a planetary-mass entity with a distinct solid structure, which renders it a satellite planet according to geophysical definitions of the term. 

What Are Craters?

A close view of some moon craters from Apollo 11.

©Digital Images Studio/Shutterstock.com

The combination of volcanism and cratering resulted in a large number of bowl-shaped formations known as moon craters. They are also called “mare.” They range in size from tiny craters less than a mile across to enormous basins that were formerly mistaken for seas. 

According to estimates by lunar scientists, only on the side of the Moon visible from Earth, there are over 300,000 craters greater than a half-mile across. The other side of the Moon is currently being mapped and is more severely cratered.

The majority of craters have a relatively distinctive round form and are occasionally ringed by circles or wrinkles. Some of them have debris strewn around them, while others have core summits. Scientists can infer the sizes, masses, and angles of flight of the impactors as they plow into the surface from the craters’ shapes.

How Did Craters Form on the Moon?

For a very long period of time, astronomers were unsure of how the Moon’s craters were created. While there were many speculations, assumptions weren’t proved until astronauts actually traveled to the Moon and returned with pieces of rock for researchers to examine. 

Since the Moon’s inception, around 4.5 billion years ago, not long after Earth was formed, volcanism and cratering have changed its surface, according to a thorough investigation of Moon rocks recovered by the Apollo 11 astronauts. 

On the young Moon’s surface, enormous impact basins were created. This allowed molten rock to rise to the surface and form enormous pools of cooled lava. As mentioned earlier, these were dubbed “mare” by scientists, which is Latin for “seas.” The basaltic rocks were created by early volcanism.

What’s the Biggest Crater on the Moon?

The largest and most well-known impact basin on the Moon is the South Pole-Aitken (SPA) Basin. It has a diameter of 1,550 miles and covers over a quarter of the Moon, which has a circumference of a little under 6,900 miles.

The basin was given this name in honor of two landmarks that are located on either side of the basin. These include the Aitken Crater in the north and the lunar South Pole in the south. Based on information from the Luna 3 and Zond 3 orbiters, the basin’s presence had been hypothesized since 1962. Although, the Lunar Orbiter program did not confirm it until the middle of the 1960s.

What Caused the Moon’s Biggest Crater to Form?

An asteroid is about to hit the Moon

The South-Pole Aitken Basin was created by a big asteroid strike.

©Marti Bug Catcher/Shutterstock.com

Scientists have noticed an enormous subterranean mass beneath the South Pole-Aitken Basin. It might be made of metal of some sort, given its density and the fact that it weighs the basin floor down by over half a mile. The obvious explanation for the presence of such mass would be a historic asteroid strike. 

Based on computer simulations of big asteroid strikes, the impact that formed the South Pole-Aitken Basin could have resulted in the lodgement of an asteroid’s iron-nickel core into the Moon’s upper mantle. This is the region between the Moon’s crust and core.

According to estimates, the South Pole-Aitken Basin developed some 4 billion years ago. The early solar system was an extremely tumultuous area. The interactions between stony and metallic bodies like asteroids and developing protoplanets (planetary embryos) happened relatively frequently. 

Therefore, it appears extremely likely that this is how the Moon’s dense subterranean mass arrived there. Nevertheless, there is also the possibility that the mass represents an accumulation of thick oxides linked to the final step of the solidification of the lunar magma ocean. 

It is believed that the Moon previously possessed a kind of ocean made of molten rock rather than water that later cooled and solidified. Therefore, it is possible that, during the procedure, the oxides were deposited in this area and formed an enormous mass.

Exploring a Crater

This basin, which is part of the younger and smaller Von Kármán Crater, is where China’s Chang’e 4 spacecraft touched down on January 3, 2019. This was the inaugural spacecraft to touch down on the far side of the Moon. 

It has examined pieces of debris that were allegedly dug up during the impact that formed the crater and is believed to have originated from deeper beneath the Moon’s mantle. This is a rare chance to examine in depth both the crater and a tiny section of the broader basin.

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The photo featured at the top of this post is © a.imagestock/Shutterstock.com

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About the Author

Kirstin is a writer at A-Z Animals primarily covering animals, news topics, fun places, and helpful tips. Kirstin has been writing on a variety of topics for over five years. She has her real estate license, along with an associates degree in another field. A resident of Minnesota, Kirstin treats her two cats (Spook and Finlay) like the children they are. She never misses an opportunity to explore a thrift store with a coffee in hand, especially if it’s a cold autumn day!

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