The Moon is older than previously thought. In fact, 40 million years must be added to its estimated age. The Earth satellite would therefore have formed at least 4.46 billion years ago. This was revealed by the lunar crystals brought back to Earth by the astronauts of the Apollo 17 Mission, the last manned one which took place in 1972, and now analyzed at the atomic level by a group of researchers led by the Field Museum of Natural History and the University of Chicago.
The study on the Moon
The study, published in the journal Geochemical Perspectives Letters, underlines the importance of the age of our satellite, given its fundamental role in the evolution of life on Earth as we know it: the Moon, in fact, stabilizes the rotation axis of our planet, and it’s why there are 24 hours in a day and the tides. More than 4 billion years ago, when the Solar System was still young and the Earth was still growing, a Mars-sized object crashed into our planet, and the collision created the Moon. “The energy of the impact melted the rock that would later become the surface of our satellite – explains Philipp Heck who coordinated the study led by Jennika Greer – so all the crystals collected must have formed after this ocean of lunar magma formed cold”.
The technique used
To be able to get the fragments to tell their age, the researchers used a technique called atomic probe tomography: “We start by sharpening a piece of the lunar sample until we obtain a very sharp fragment. Then – says Greer – we use a laser to evaporate atoms from the surface of that tip. The speed at which the atoms move tells us how heavy they are, which in turn tells us what they are made of.” Understanding the exact composition of the crystals is essential to trace the moment of their formation which, according to the results, is 4.46 billion years ago: the Moon, therefore, must be at least that age.