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HOUSTON — A burning smell from the toilet is not something you'd want to experience on Earth, so when it happened to NASA's Artemis 2 astronauts on the way to the moon — well, you can bet Mission Control was listening.

Late Friday (April 3), as NASA's Artemis 2 mission passed the halfway mark to the moon, the four astronauts on board reported a burning smell coming from their novel Orion space toilet.

"For me, it was some sort of burning odor, and then it was definitely in the hygiene bay," said Artemis 2 mission specialist Jeremy Hansen of the Canadian Space Agency. "And when I opened up the hygiene bay, the rest of the crew could smell it pretty much immediately." (You can see our latest updates on our Artemis 2 mission updates page.)

NASA astronaut Christina Koch, also an Artemis 2 mission specialist, told Mission Control that the smell seemed to originate from the toilet, and was similar to an odor the crew smelled on the first day of the mission.

Koch described it as "the kind of burning heater smell," something that Hansen also confirmed.

Hansen said he and the crew had been warned before flight of the potential for an odor similar to "when you turn on a heater that's been sitting for a while and … you smell that burnt smell that comes from that," he said. "And I do think it smells similar to that."

Mission Control initially suspected the odor could be caused by orange insulation around the door to the hygiene bay containing Orion's toilet, but did say the astronauts could keep using the bathroom as usual.

"Overall, we don't have any major concerns," Mission Control radioed the crew.

The Artemis 2 crew had a bit of trouble with their toilet on day one of their mission, when Koch worked with Mission Control to restore it quickly to service.

The astronauts were advised overnight to use their contingency bags to collect urine if they had to pee, rather than the toilet. But that was due to an issue with the primary vent on Orion that dumps wastewater overboard, which may have built up ice around it. Mission Control was working on ways to heat the nozzle up with sunlight and heaters to clear any ice today.

The four Artemis 2 astronauts — NASA commander Reid Wiseman and pilot Victor Glover round out the crew — woke up today at 12:35 p.m. EDT (1635 GMT) for Flight Day 4 of their 10-day mission to the moon to the tune of "Pink Pony Club" by Chappell Roan, which Mission Control played as a wakeup call but cut off before the chorus.

"We were all eagerly awaiting the chorus," Wiseman said.

NASA shared some stunning new images of Wiseman and Koch gazing at Earth from Orion's windows as they continued leaving their home planet behind.

The astronauts are spending today brushing up on lunar geography to prepare for the moon observations they will make on Monday (April 6) when they make their closest approach to the moon. The crew will fly by the moon, coming within just over 4,000 miles (6,400 kilometers) of the lunar surface before swinging back toward the Earth.

All four of the astronauts will also get to manually fly Orion today, NASA officials said.

Mission Control called off a planned maneuver today to refine Orion's course toward the moon, apparently because it's still on such a precise flight path. As of press time, Orion was about 107,922 miles (173,683 km) from the moon and closing, and about 172,217 miles (277,156 km) from Earth.

Artemis 2 is NASA's first crewed flight of the Orion spacecraft (the crew named theirs "Integrity"), and its flawless launch on April 1 was the first crewed flight of NASA's Space Launch System megarocket.

The flight is NASA's first astronaut mission to the moon since Apollo 17 in 1972, and the vanguard flight for the agency's plans to return humans to the lunar surface by 2028 and set up a permanent moon base by 2032.

The only Lego Technic NASA Artemis Space Launch System Rocket, once built it can 'launch' thanks to the clever Technic engineering mechanisms inside. It stands 27.5-inches (70 cm) tall but is made from only 632 pieces, making this suitable for ages 9+, compared with the adult-oriented (and $260) static Lego Icons NASA Artemis Space Launch System (10341) model.

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