Our closest neighbour, the Moon

The Moon is our only natural satellite. Despite its proximity to Earth and the fact that man has visited the Moon, there are still many questions about the Moon. Scientists still struggle to answer some fundamental questions like: What is the nature of the Moon’s core? What is the structure of the mantle? And, despite recent evidence of substantial water on the Moon, why is there so much less than on Earth? According to the most accepted theory, the Moon formed roughly 4.5 billion years ago, when a large body the size of Mars hit the young Earth. The debris of both the impacting body and the Earth’s outer layers formed our Moon. Almost immediately, gravitational forces
locked it into synchronous rotation, with one side always facing the Earth.

The Moon probably has an iron and nickel core, which is quite a bit smaller in proportion to its radius than that of the Earth. The core is probably surrounded by a mantle and finally a crust. The crust on the far side of the Moon is about twenty kilometres (13 miles) thicker than on the side facing Earth, this is one third of the thickness. Scientists still have no idea what could have caused this. In its early years there was volcanism on the Moon. Dark volcanic plains cover much of the Moons near side, while the far side is practically devoid of them. Although the surface lava has long since cooled, the interior remains hot. It is believed that the inside of the Moon still has temperatures of 1.300 degrees Celsius (2.400 degrees Fahrenheit) and it will probably take several hundred million years before the interior finally cools off. The Moon seems hotter on the side that faces the Earth; scientists now argue if this is because the crust on this side is thinner, or that the crust is thinner because of the heat. It is a bit like the question of the chicken and the egg.

The Moon also has seismic activity. These moonquakes are shallow ones and less violent than some recorded on Earth. The largest ever recorded registered 5.9 on the Richter scale, modest by Earth standards but still a good-sized shake. These moonquakes are partially caused by tidal stresses (induced by the changes in the Moon’s distance to Earth) and the shrinking of the Moon while it slowly cools down.

Enough questions still about our closest neighbour even though all its craters are mapped and even the far side has been explored. Even if lunar science would get priority, the Moon will continue to guard its secrets. But not forever, once we will have colony on the Moon and eventually it will have to surrender its secrets. Until then we can always look up to its familiar face and see it go through its monthly phases.

Regards from the bush
Miriam