It might not look like much now, but scientists claim that the Earth's moon may have supported life 4 billion years ago, around the same time that life was starting on Earth.

If life on the moon once existed, how did it end up as the dead rock that it is now?

Life On The Moon Once Existed, 4 Billion Years Ago

A study published in the Astrobiology journal identified two periods in the distant past of the moon when it possibly hosted life, coinciding with when life was also forming on Earth.

According to the research, the first event was shortly after the moon started to form from a debris disk 4 billion years ago, as it was releasing water vapor and other types of volatile gas in massive quantities. The second event was 3.5 billion years ago, when the moon's volcanic activity reached its peak.

In both events, the volatile gases were believed to have created pools of liquid water on the moon's surface and a dense atmosphere that may stay in place for millions of years. The atmosphere was also believed to have a magnetic field that protected any life on the moon's surface from destructive forces such as the solar wind.

"There could have actually been microbes thriving in water pools on the Moon until the surface became dry and dead," said Washington State University astrobiologist and study author Dirk Schulze-Makuch.

In comparison, the earliest traces of life on Earth were between 3.5 billion and 3.8 billion years ago, according to discovered cyanobacteria fossils. It is believed that meteorites brought water to Earth during the early years of its formation, and it is possible that these same meteorites bounced off the surface of the Earth and landed on the moon, bringing with it water and microbes.

How Did The Moon Die?

The study was based on data from space missions, as well as analysis of soil and rock samples from the moon. The results showed that the moon is not as dry as previously thought, and far from its current state without an atmosphere, but rather with a thin layer of gases including potassium and sodium that attempt to function like one.

It is believed that moon stopped being habitable around 3 billion years ago, when it cooled too much to keep on giving off the gases needed to maintain its atmosphere. The moon also lost its magnetic shield, opening it up to solar winds.

To know more on how the moon died, as well as to confirm that it was indeed capable of supporting life billions of years ago, Schulze-Makuch and coauthor Ian Crawford, Professor of Planetary Science and Astrobiology from the University of London, proposed a more aggressive lunar exploration program in the future. In fact, Schulze-Makuch and Crawford have already expanded their lunar research group to start working on some of the experiment that they have in mind.