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Do you know that the largest verified impact craters on Earth are more than 100 km wide? And the largest of them, Vredefort Crater, being an astounding 300 km wide? Still, these giants are no match for the largest of all craters of the Moon.
So what is the largest of all craters of the Moon? The South Pole-Aitken Basin, which also happens to be the largest known crater in the Solar System, has a diameter of – hold on to your eyeballs – over 2,000 km! It’s also very deep, at 13 km. That’s even much deeper than the deepest point on Earth, some 11 km below the surface of the ocean – Challenger Deep.
But wait a minute. Before you start to think all craters on the Moon are nearly this large, let me assure you they’re not. Most of the really large ones are not even half as large as this. They’re usually only between 400 to 500 km wide. That’s the same order of magnitude as our own big ones.
So if you take out the South Pole-Aitken Basin, it would be safe to say that the craters of the Moon and the craters of the Earth have more or less the same dimensions. In fact, the craters of the Moon are even about as old as those on Earth. For example, Vredefort is estimated to be at least 2 billion years old. That’s about the same age as the oldest known lunar craters.
And why not? After all, if you look at them in astronomical scales, the two are definitely very close to one another. Thus, the family of rocks that may have impacted the Moon’s surface may have also impacted Earth’s.
The only big question that always remains is: Why then do we have so few of these craters? Aren’t we supposed to have even more, considering the size of the Earth compared to the Moon?
Alright, remember your Earth Science 101 that talks about plate tectonics and how they have formed the towering Himalayas, the sinister depths of the Marianas Trench, and possibly even entire continents? No doubt therefore, these same activities may have concealed a substantial number of impact craters.
The Moon, as we know it, is not exposed to such activities. Furthermore, there is very minimal erosion there due to the absence of water on the surface. Therefore, all craters of the Moon, no matter how old, remain preserved.
Here’s a list of popular craters on Earth from Universe Today.
Come October 9, 2009, LCROSS will perform a lunar impact. Find out which crater NASA has chosen for the impact. If you want to know more about the largest crater on the Moon, NASA’s got the right stuff.
There are some interesting episodes from Astronomy Cast that we’d like to recommend:
The Source of Atmospheres, the Vanishing Moon, and a Glow After Sunset
The Moon, Part 1