'Man in the Moon' Is More Ancient Than We Thought

Scientists believe the moon formed 4.5 billion years ago based on studies of lunar rocks. But dating the lunar surface is less cut and dried. As only so many lunar samples are returned to Earth, scientists have traditionally counted craters as a way of dating sections of the lunar crust. With no erosion or plate tectonics on the moon to erase craters as on Earth, scientists can count craters and estimate how much time it took them to form, per Live Science. Here's the problem: this method has produced dates that don't match up with those revealed through analyses of rocks collected during the Apollo missions. Luckily, researchers say they've resolved the discrepancy and in doing so, have pushed back the date of portions of the lunar crust by up to 200 million years.

In a breakthrough, researchers in France and Norway essentially merged the two dating methods. They examined lunar samples collected during the Apollo, Luna, and Chang'e missions, but also counted craters around the sites where the rocks were found, per Live Science. They then generalized the information so it could be applied to sections where lunar samples have not been retrieved. "What we have done is to show that large portions of the lunar crust are around 200 million years older than had been thought," says Stephanie Werner, a geologist at the University of Oslo's Centre for Planetary Habitability, whose research has been accepted for publication in the Planetary Science Journal.

"The new system of dating changes the age of all areas of the Moon's surface—not uniformly, but with the oldest surfaces showing greatest changes," according to a release. Mare Imbrium, a massive crater eventually filled by lava flows so as to form the right eye of the landform known as the Man in the Moon, is now thought to be 4.1 billion years old, rather than 3.9 billion years. "This is an important difference," says Werner. "It allows us to push back in time an intense period of bombardment from space, which we now know took place before extensive volcanic activity that formed the 'Man in the Moon' patterns." As the same bombardment is likely to have affected Earth, and possibly Mars as well, the research could hold clues to the geological history of those planets, per Earth.com. (More moon stories.)