Exploration at its greatest
The Moon – that inconstant orb; a glorious bright light in our night sky; an ancient vehicle for human myths and deities; and now a world become known. For thousands of years before the rise of the scientific method, humans gazed at Earth’s one natural satellite, wondered at its nature and worked it into their stories as they struggled to understand their universe and its impact upon them. It was only with the invention of the telescope that the true nature of our satellite world began to be revealed.
When casually viewed from Earth, the Moon exhibits a mottling of dark grey patches against a lighter grey landscape. What was not realised until Apollo’s rocks were returned was that these features are a window into the earliest era of the solar system. We now know that the light grey areas, rough and heavily cratered, form an extremely ancient highland terrain that dates beyond four billion years ago. The dark patches, called mare (pronounced hnaa-ray’, plural maria), are great plains of basalt that solidified from immense effusions of the Moon’s particularly runny lava that flowed more than three billion years ago. In many cases, these outpourings of molten rock filled large circular basins that had been excavated some time previously by cataclysmic impacts. Peppered across its face are bright sprays of material that emanate from some of the craters. These are rays of ejecta – shocked and pulverised rock thrown out from more recent high-speed collisions by somewhat smaller bodies. Given immense time, these rays will fade and darken to match their surroundings.