why does mercury have more craters than earth
All of the planets in our Solar System have had a lot of craters. This was especially true in the past when there were many more asteroids traveling in our solar system than there are today. On planets like Venus, Earth, and Mars, we do not see as many craters because most of them have been eroded away by wind, rain, volcanic activity, and other forces.
On the giant gas planets, Jupiter, Saturn, Uranus, and Neptune, we do not see any craters because there is no visible solid surface for the meteors to hit. On Mercury, where there is no atmosphere, there is no weather to erode away the craters, so most of the craters are still visible.
In the case of the moon, most of the craters were formed in the late bombardment and as such are very old- over four billion years ( ).
The early Earth would certainly have been hit just as frequently. The relative size of the two bodies means taht the geological processes within each differed. The moon is geologically dead. In contrast, the Earth is geologically active.
It is this activity that is key to understanding why there are so few remnants of early craters. The Earth s crust is made of two layers- oceanic and continental. Oceanic crust is cyclical, with the cycles running around 200 million years. Any strike on this crust would in a geologically short period be erased when the crust subducts beneath a continent.
Continental crust has more permanence because it doesnt subduct. However, it is exposed to forces- erosion due to rain and wind and ice (see here for more: ), as well as splitting and suchering- which would gradually degrade the remnants of a crater, especially those that are billions of years old.
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