Moon 100 Million Years Younger than Previously Believed

The moon is over 100 million years older than previously believed, scientists have said, with experts saying it is as young as 4.4 billion.

Richard Carlson, from the Carnegie Institution of Washington, said improved data shows the moon is between 4.4 and 4.45 billion years old, rather than 4.56.

Scientists made the announcement at a Royal Society meeting in London entitled Origins of the Moon.

It is widely believed that the moon was formed from a giant impact but a deeper understanding has always been hindered for a number of reasons. The meeting will discuss current beliefs about the moon and how it relates to Earth.

Astronomers have studied the moon and tried to estimate its age for many years by analysing lunar crustal rocks, but technical issues has always meant it is difficult to accurately estimate how old it is.

However, new technology has allowed scientists to date the rocks with greater prevision and have found the moon is around 100 million years younger than was thought.

Models suggest planets form over a couple of million years. Small celestial bodies violently collide and fuse to form planetesimals.

Erase earlier events

Heating caused by the decay of radioactive elements causes a melting process that results in iron metal segregating to the centre of the forming planetesimal, while the most volatile elements move into the atmosphere.

If the planetesimal is too small, it does not have enough gravity to hold its atmosphere and escapes into space. It is though Earth was likely formed from a collection of planetesimals that had already lost their atmospheres.

Explaining the process, Carlson compared a planet to the asteroid Vesta, which was formed so quickly that its age was frozen precisely in its rocks. However, the moon and Earth took longer to form: "Its growth tends to erase, or at least cloud, the memory of earlier events," he said.

Scientists believe the moon formed after a large impact into the "proto-Earth", which set the age of the moon.

Carlson said the moon being younger than previously thought will affect our understanding of the Earth: "There are several important implications of this late Moon formation that have not yet been worked out, for example, if the Earth was already differentiated prior to the giant impact, would the impact have blown off the primordial atmosphere that formed from this earlier epoch of Earth history?"