On Saturday, NASA scrubbed its second attempt to launch its Artemis I mission into lunar orbit. This time, the culprit was a liquid hydrogen leak that showed up while the team was loading the rocket's core stage.

According to the space agency, the leak occurred "while loading the propellant into the core stage of the Space Launch System rocket. Multiple troubleshooting efforts to address the area of the leak, by reseating a seal in the quick disconnect where liquid hydrogen is fed into the rocket, did not fix the issue." 

Those troubleshooting efforts occurred over several hours, as the Artemis team zeroed in on sealing the spot where the leak was coming from, starting with two tries at what you might call "turning it off and on again." The supercold hydrogen fuel was halted in its tracks, the tank connector was warmed, then the fuel flow was resumed in hopes of sort of steam-sealing the leak. This wasn't working. Then, NASA redirected efforts to a new solution: pumping the tank with helium. Nope. The leak persisted.

So, at approximately 11:17 a.m. ET --  roughly three hours before Saturday's launch window was set to open -- launch director Charlie Blackwell-Thompson made the call to scrub Saturday's attempt.

This is the second time the Artemis I mission has been delayed. Liftoff attempt No. 1 was scheduled for Monday, but Blackwell-Thompson had to call a scrub because of an unyielding problem with what's known as an engine bleed test. This process is meant to allow the engines to chill to the right temperature by releasing a small amount of the fuel.

The next date on NASA's initial list of liftoff day options is Monday, Sept. 5. But we've still yet to hear about launch rescheduling. We'll update this article as soon as we know more.

Read more: NASA's Artemis I Moon Launch: What You Need to Know About the Mega Mission