Short answers, pulled from the story.
Radiometric dating places mare basalts between 3.16 and 4.2 billion years old. Some flows from the Chang'e-5 mission show basalt could be only 2.03 billion years old. Most eruptions occurred between 3 and 3.5 billion years ago.
Thomas Harriot became the first person to use a telescope for Moon observations in 1609. He created a detailed map in 1611 but kept it secret. Galileo Galilei released Sidereus Nuncius in 1610 with his own findings.
Mare basalts cover about 16% of the lunar surface and appear mostly on the side visible from Earth. Data from the Lunar Prospector mission shows heat-producing elements concentrate in Oceanus Procellarum. This unique geochemical province is called the Procellarum KREEP Terrane.
Ancient Greek philosophers like Thales and Democritus believed the Moon was rocky and earth-like. They argued there were no seas on its surface. Roman historian Pliny the Elder used the word mascula to describe lunar spots and thought the Moon was covered in mud rather than water.
Scientists group them by major element chemistry into three series. High-Ti basalts contain up to 15 weight percent titanium dioxide. Very-low-Ti groups exist but are rare.