Four astronauts could leave the International Space Station on Sunday without their replacement team having arrived to take over, NASA announced Thursday, but the timing remains uncertain due to weather conditions.

The four members of the Crew-2 mission, including a French and a Japanese astronaut, are due to return to Earth this month after spending about six months on board the ISS.

Normally they would have to wait for four other astronauts—three Americans and a German from the Crew-3 mission—to arrive aboard the space station to take their place.

But the takeoff of the next mission's rocket, which had already been postponed several times and had been rescheduled for this weekend, was once again canceled because of unfavorable weather conditions, NASA said in a statement.

As a result, the space agency is now considering returning Crew-2 to Earth before Crew-3 launches.

"The earliest possible opportunity for undocking" the capsule to bring Crew-2 back to Earth would be at 1:05 pm Sunday Florida time (1705 GMT), NASA said.

In the 1998 Hollywood blockbuster "Armageddon," Bruce Willis and Ben Affleck race to save the Earth from being pulverized by an asteroid.

While the Earth faces no such immediate danger, NASA plans to crash a spacecraft traveling at a speed of 15,000 miles per hour (24,000 kph) into an asteroid next year in a test of "planetary defense."

The Double Asteroid Redirection Test (DART) is to determine whether this is an effective way to deflect the course of an asteroid should one threaten the Earth in the future.

NASA provided details of the DART mission, which carries a price tag of $330 million, in a briefing for reporters on Thursday.

"Although there isn't a currently known asteroid that's on an impact course with the Earth, we do know that there is a large population of near-Earth asteroids out there," said Lindley Johnson, NASA's Planetary Defense Officer.

A US federal judge on Thursday ruled against Blue Origin brought by Jeff Bezos' company in a bid to overturn a NASA contract awarded to rival SpaceX, founded by Elon Musk, to build the next craft for Moon landings.

The ruling put an end to a months-long legal battle that had prevented the US space agency from working with SpaceX on the lunar lander called Starship, which will allow Americans to return to the Moon as part of the Artemis program.

"NASA will resume work with SpaceX under the Option A contract as soon as possible," the agency said in a statement after the ruling.

In April, NASA announced it had awarded the contract to Musk's company—a deal worth $2.9 billion.

But Blue Origin filed a complaint about the decision to the Government Accountability Office (GAO), saying the bidding process had been unfair and that NASA should have offered more than one contract.