Moon may have been habitable in distant past: Study

Conditions on the Moon were favourable to support life shortly after the lunar body formed 4 billion years ago, and again during a peak in volcanic activity around 3.5 billion years ago, according to a study.

The study, published in the journal Astrobiology, suggests that there may have been two early windows of habitability for the Moon.

During both periods, planetary scientists think the Moon was spewing out large quantities of superheated volatile gases, including water vapour, from its interior.

According to the researchers at the Washington State University in the US, this outgassing could have formed pools of liquid water on the lunar surface and an atmosphere dense enough to keep it there for millions of years.

"If liquid water and a significant atmosphere were present on the early Moon for long periods of time, we think the lunar surface would have been at least transiently habitable," said Dirk Schulze-Makuch, an astrobiologist at Washington State University.

The research draws on results from recent space missions and sensitive analyses of lunar rock and soil samples that show the Moon is not as dry as previously thought.

In 2009 and 2010, an international team of scientists discovered hundreds of millions of metric tonnes of water ice on the Moon.

There is strong evidence of a large amount of water in the lunar mantle that is thought to have been deposited very early on in the Moon's formation, researchers said.

The early Moon is also likely to have been protected by a magnetic field that could have shielded life-forms on the surface from deadly solar winds, they said.

Life on the Moon could have originated much as it did on Earth but the more likely scenario is that it would have been brought in by a meteorite, Schulze-Makuch said.

The earliest evidence for life on Earth comes from fossilised cyanobacteria that are between 3.5 and 3.8 billion years old.

During this time, the solar system was dominated by frequent and giant meteorite impacts. It is possible that meteorites containing simple organisms like cyanobacteria could have been blasted off the surface of the Earth and landed on the Moon.

"It looks very much like the Moon was habitable at this time. There could have actually been microbes thriving in water pools on the Moon until the surface became dry and dead," Schulze-Makuch said.