A new study at NASA has found that our moon had a more prominent atmosphere than it does today – around 3 to 4 billion years ago – when intense volcanic eruptions spewed giant cloud of gas above the surface faster than they could escape to space.

The surface of the moon is covered in dead volcanoes, impact craters and seas of basalt called maria, which were formed when magmatic plumes from inside the moon erupted to the lunar surface. And the surface, as Scientific American puts it – is so thin it’s not even technically an atmosphere— instead, it’s considered an “exosphere,” with molecules, though gravitationally bound to the moon, are too scanty to even behave like a gas.

Artistic impression of the Moon, showing volcanoes erupting, venting gases and producing a thick atmosphere. Credit: NASA MSFC

Samples from the maria collected by the Astronauts from the Apollo missions indicate that magmas carried “gas components, such as carbon monoxide, the ingredients for water, sulfur, and other volatile species.”

For the study, the team calculated the amounts of gases that that rose from the erupting lavas from the lunar surface and showed that those gases accumulated around the Moon to form a transient atmosphere. They also found that the atmosphere was thickest during the peak in volcanic activity about 3.5 billion years ago. And once it created, it lingered for 70 million years before being lost to space. During that time, the moon was 3 times closer to Earth than it is today, and therefore it would have appeared nearly 3 times larger in the sky.

Researchers say the findings may have important application for future exploration of the moon. They also suggest that volatiles from the atmosphere may have been trapped into cold, permanently shadowed regions near the lunar poles and, thus, “may provide a source of ice suitable for a sustained lunar exploration program.”

The study, entitled “Lunar volcanism produced a transient atmosphere around the ancient Moon” has been published in the journal Earth and Planetary Science Letters.