Iconic 'Man in the Moon' could be 200 million years older than we thought

Unlike Earth, which has undergone significant geological changes, the Moon has remained relatively inactive. This means that the craters caused by asteroids and comets over time have not eroded, allowing scientists to study their impact history. 

"Looking at the signs of these impacts on the Moon shows what Earth would be like without the geological churning of plate tectonics which took place here on Earth," explained author Professor Stephanie Werner from the University of Oslo's Centre for Planetary Habitability in a press release.

"What we have done is to show that large portions of the lunar crust are around 200 million years older than had been thought".

The researchers had noticed discrepancies between crater counting, the standard method used to determine the Moon's surface age, and the ages obtained from analyzing rocks collected during the Apollo missions. They noticed these inconsistencies, particularly in the Moon's light areas, called the Highlands.

To reconcile these differences, the team individually dated Apollo samples and correlated them with the number of craters in the surrounding area. 

They also compared the samples with spectroscopy data from various Moon missions. Through this extensive work, they adjusted the age estimates and pushed back the surface age by up to 200 million years.

For instance, the Imbrium Basin, which contains the Mare Imbrium (the "lunar sea" visible on the Moon's top left), was found to be 4.1 billion years old instead of the previously estimated 3.9 billion years. 

It's important to note that this adjustment only affects the age of the Moon's surface, not the overall age of the Moon itself.

This new dating system reveals a period of intense bombardment from space before volcanic activity shaped the Moon's distinctive features, such as the patterns resembling the "Man in the Moon." 

The findings have broader implications for understanding the early history of our solar system. For instance, the researchers believe Earth likely experienced a similar early bombardment.

"Such a heavy bombardment period must have affected the origin and early evolution of life on Earth and potentially other planets such as Mars," commented Prof. Audrey Bouvier from the University of Bayreuth, Germany, who was not involved in the study.

 "Bringing back rock samples from Jezero Crater on Mars will be the next giant leap forward to search for signs of ancient life on another planet in the Solar System, and when."

In other words, understanding the Moon's impact history and keeping up with future missions to Mars are significant in revealing insights about our planet's past.

The findings were presented at the Goldschmidt Geochemistry Conference in Lyon, France, and are yet to be peer-reviewed.