NASA began a two-day practice countdown Saturday leading up to the fueling of its new moon rocket, a crucial test that will determine when four astronauts blast off on a lunar flyby.

For the first time in more than 60 years, NASA has two human spaceflight crews waiting in quarantine at the same time ahead of launch: the four Artemis II astronauts and the SpaceX Crew-12 quartet.

“You can go up there, and it’s almost a Rosetta Stone you can read that tells you about the solar system’s history,” said Haluska, which could lead to many discoveries, some even useful back on Earth.