Astronauts could live inside caves on the moon left behind by lava, a Nasa scientist has claimed.
Experts from the space agency discussed the possibility of lunar habitation as part of an "ask me anything" session on Reddit ahead of the next planned US moon mission in 2024.
Dr Daniel Moriarty, a post-doctoral lunar scientist, suggested lava tubes on the moon's surface could provide a shelter for astronauts.
Lava tubes are long tunnel-like caves left by previous molten activity on the moon.
It comes after Nasa announced its next mission to the moon will be called Artemis.
Dr Moriarty said that Nasa will likely work around the moon's natural structure when preparing its surface for humans.
"I do not think we're going to be able to change anything about the surface of the moon much," Dr Moriarty wrote.
"Instead, I think it makes sense to work within some of the structures and resources that are already there.
"For instance, it could be useful to establish a base near a permanently-shadowed polar region in order to take advantage of surface water that's there.
"Alternately, it could be interesting to set up shop within a pre-existing lava tube, which could provide astronauts with some shielding from temperature variations and incoming solar radiation."
Nasa boss Jim Bridenstine announced plans to have astronauts return to the moon within 10 years earlier this year.
"We will go with innovative new technologies and systems to explore more locations across the surface than was ever thought possible," he said.
"This time, when we go to the moon, we will stay. And then we will use what we learn on the Moon to take the next giant leap – sending astronauts to Mars."
In March, US President Donald Trump accelerated the next lunar mission up by for years to 2024.
The mission includes plans to visit the moon's south pole for the first time and send the first female astronaut to its surface.
Nasa said it was confident of achieving these goals during the Reddit question and answer session.
They said the agency was used to "big challenges" and new budget provision made it "doable".
There have been six crewed landings on the moon conducted by the US, which were between 1969 and 1972.