The 2024 U.S. Open will be one Coco Gauff would like to forget sooner rather than later.

The defending champion failed to advance past the Round of 16 on Sunday afternoon, losing to fellow American Emma Navarro, 6-3, 4-6, 6-3.

Navarro took care of business in the first set, and the second was a back-and-forth battle early. With the set tied at three, Navarro broke Gauff’s serve to go up 4-3, putting Gauff on thin ice.

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But it wasn’t thin enough as Gauff returned the favor by breaking Navarro’s serve. Gauff then took a 5-4 lead and then broke Navarro again to take the match to a third set.

Gauff won the first game, with all signs pointing to momentum on her side. But it didn't carry over as Navarro took the next three. The two then alternated games, putting Navarro up 5-3 with Gauff serving, but that wasn’t much of an advantage for the reigning champ, who double-faulted three times to help Navarro advance to the quarterfinals.

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Gauff had 19 double faults in the match, 11 of which came in the final set. After her final one, she threw her racket down in anger.

It's the second grand slam in a row she lost in the Round of 16 after advancing to at least the semifinal in her previous three. It's also the sixth year in a row the reigning champ failed to make it to the quarterfinals. No reigning champ has made it to a semifinal since Serena Williams in 2015.

Navarro next faces Paula Badosa of Spain on Tuesday; it's her second straight quarterfinal in what's been a career-year for the 23-year-old, who had never made it past the second round of a grand slam until this year.

She's advanced to at least the Round of 16 in each grand slam this year, with her best finish being the quarterfinal in July's Wimbledon.

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A NASA astronaut at the International Space Station (ISS) on Saturday reported hearing a "strange noise" coming from the Boeing Starliner spacecraft just days before it is set to leave the station and return to Earth on autopilot.

The astronaut, Butch Wilmore, radioed Mission Control at Johnson Space Center in Houston to inquire about the noise. 

On an audio recording of the exchange, Wilmore holds up a phone to the speakers so that Mission Control could hear the noise he was referring to. A pulsating sound emanating at steady intervals can be heard through Wilmore’s device. 

"Butch, that one came through," Mission Control says after not hearing it the first time. "It was kind of like a pulsating noise, almost like a sonar ping." 

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"I’ll do it one more time and let you all scratch your heads and see if you can figure out what’s going on," Wilmore tells Mission Control, playing the sound one more time. 

Mission Control tells Wilmore the recording will be passed along and that they'll let him know what they find.

Wilmore clarifies that the sound is emanating from the speaker inside the Starliner. 

The bizarre sound was first reported by Ars Technica, which cited a recording first captured and shared by Michigan-based meteorologist Rob Dale. 

Fox News Digital has reached out to Mission Control and Boeing to inquire if the source of the sound has been identified. 

Starliner is slated to undock from the ISS, empty, and attempt to return on autopilot with a touchdown in the New Mexico desert. 

NASA decided it was too risky to bring back Wilmore and Suni Williams until February. The astronauts were originally slated for a weeklong trip in early June, but the mission has been mired in problems after thruster failures and helium leaks.

Boeing had counted on Starliner’s first crew trip to revive the troubled spacecraft program after years of delays and ballooning costs. The company had insisted Starliner was safe based on all the recent thruster tests in both space and on the ground.

The Associated Press contributed to this report.