It's been 45 years since Americans visited the Moon, but if NASA and its Russian equivalent, Roscosmos, have their way, that could change within a decade or two. On Wednesday, the two space agencies signed a statement indicating their intent to work together to establish a new space station that will orbit the Moon. It's a key milestone in NASA's longer-term plan to send humans to Mars.
The full text of the agreement is not currently available, and the publicized details are scant, so it's difficult to tell exactly what the partnership will look like, or the timeline on which it will unfold.
The project is called a deep space gateway and was announced earlier this year by NASA. The gateway would be a sort of home base in lunar orbit, including residential quarters and some research facilities. Spacecraft would dock with the gateway just as they do with the International Space Station, which has been orbiting Earth since 1998.
In all probability, the deep space gateway would need to be constructed from modules in space, since there's no way to launch such a large structure, even on the heavy-class Space Launch System rocket that NASA is still building and testing.

NASA has seen several priority shifts over the past decade or so: President George Bush wanted the agency to focus on the moon, President Barack Obama was keen on Mars, and President Donald Trump has been seen as pushing the focus back to the moon. A lunar base would be valuable under either scheme, serving as a testing ground and waystation for missions destined to Mars or asteroids.
"Statements such as this one signed with Roscosmos show the gateway concept as an enabler to the kind of exploration architecture that is affordable and sustainable," said Robert Lightfoot, NASA's acting administrator, in a press release about the agreement.
As usual, NASA is not flaunting its timelines, but in the original deep space gateway plan, it proposed a one-year crewed mission at the base by the end of the 2020s. To help meet that goal, in addition to the Roscosmos partnership, both agencies are working with national commercial space companies to help develop new technologies.
Rumors of the partnership emerged last week in anticipation of the International Astronautical Congress being held in Australia this week, which also saw the announcement of a new Australian space agency.
The International Space Station includes not only NASA and Roscosmos, but also the European, Japanese and Canadian space agencies. Wednesday's agreement doesn't address whether or how these other space agencies will be brought into the deep space gateway project. However, according to comments by the head of Roscosmos at the partnership announcement, the project could also be introduced to China, India, Brazil and South Africa, which have a separate agreement with Russia about space exploration.