The Moon Crater's

When it rains on the moon it isn’t water falling from clouds that strike the surface, but rather meteors that hurtle through space as missiles with a mission. When they strike the surface of the moon, they leave quite an impact, one which can last for a very, very long time. The craters of the moon, of which there are many, have often piqued the curiosity of mankind from long before they were understood.

A Look at The Moon Crater's

The craters of the moon were named by Galileo after he built his first telescope and turned it heavenward. The name comes from the Latin word for “cup”, which is a fairly accurate first impression of the bowl like depressions on the surface of Earth’s closest neighbour. The dominate theory of how craters ended up on the moon was not settled upon until the 1940’s, and until then there were a few competing theories, including glacial activity, volcanic activity, and meteoric activity. It turns out that the last idea is the accurate one.

Impact craters are formed on the surface of the moon exactly as it sounds, when a smaller object impacts the larger. The force of the impact causes shockwaves in the surrounding surface material, which rebound and force parts of the surface up and out, ejecting it into space in some instances, and also on to the surrounding surface. In some cases part of the shockwave energy bounces back from the centre of the impact, creating a peak of material in the middle of the impact crater. Interestingly a low-angle impact creates a peak that is off centre, allowing lunar geologists to point out those craters formed in such a manner.

Looking at craters on the moon is part of seleonography, the study of the moon’s geography, and has yielded a lot of information about the moon. The ejecting material formed by impacts settle on the surface in layers called regolith. Some craters have dark halos of basalt material that come from when the regolith has covered a basalt mare, or a plain of dark basalt material, and then is disturbed by the impact of a meteorite.

Crater Size

Some craters are practically microscopic, while others are quite large indeed. The largest is the South Pole-Aitken Basin, which has a diameter of about 2,500 km and drops 13 km deep. The size of a crater seems to be indicative of its age as well, at least for the most part. It is believed that a period of heavy bombardment consistent in the solar system took place long ago, and that closer to the present time, impacts were made by smaller objects.

In many cases, craters are impacted by second and subsequent meteors, leaving behind younger crates. It is generally believed that the crates on top are the younger, and the resulting disturbance of a second impact provides erosion—in fact, impact craters are the major force of geological change on the moon.

Crater Placement

In some cases when large enough meteor hits the material ejected out of the new crater returns to strike again, forming secondary craters. Enough impacts of this nature in one area create valleys. In other cases objects break up as they approach the moon’s surface and leave a string of impacts, called catena, or crater chains.

Understanding how craters are formed on the moon has provided a good grasp of impact crater theory, which is applied to the study of other bodies in space, specifically terrestrial planets.