Why is the International Space Station leaking? What to know after Axiom mission delayed

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A leak on a remote outpost orbiting about 250 miles above Earth may sound alarming, but not to worry: The seven astronauts aboard the International Space Station are not in harm's way.
But until the air leak detected on the laboratory's Russian segment is resolved, NASA has opted not to send any other people to dock at the station. That means an indefinite delay for a four-person commercial spaceflight.
The postponement is nothing new for Axiom Mission 4, which has already experienced previous delays due to bad weather and issues with the SpaceX Falcon 9 rocket selected to get it off the ground. Axiom Space, headquartered in Houston, Texas, is the company behind the private mission – its latest in a series of human spaceflights in partnership with both NASA and SpaceX.
While the astronauts aboard the station are not in danger, small cracks on the ISS in recent years, particularly on the aging Russian segment, have contributed to the decision to retire the station by 2030.
Here's what to know about the latest leak on the space station, and how it will effect the launch of Axiom Mission 4.
The International Space Station has been stationed in low-Earth orbit for more than 25 years, typically about 250 miles high, where it has been home to astronauts from all over the world.
The orbital laboratory is operated through a global partnership of space agencies, including NASA, Roscosmos, the European Space Agency, the Japan Aerospace Exploration Agency (JAXA) and the Canadian Space Agency (CSA).
More than 280 spacefarers from 23 countries have visited the International Space Station, including 169 from the United States alone, according to NASA. Bigger than a six-bedroom house, the outpost has six sleeping quarters, two bathrooms, a gym and a 360-degree view bay window.
The launch of the Axiom mission had already been delayed to allow SpaceX to repair a liquid oxygen leak found on the Falcon 9 rocket, NASA has said.
Now, the mission is being delayed indefinitely after a "new pressure signature" was found on the station's Zvezda service module, a more than 2-decade-old core compartment, according to NASA.
The discovery came after cosmonauts aboard the space station recently performed inspections of the pressurized module's interior surfaces, sealed some area and measured the current leak rate.
The segment now is holding pressure, but NASA said the Axiom Mission 4 delay will provide additional time for the U.S. space agency to evaluate the leak with Roscosmos and determine next steps.
NASA deferred additional questions about the leak to Roscosmos.
A new launch date for Ax-4 has not yet been announced as of Friday, June 13.
Axiom Mission 4, also known as Ax-4, is a commercial spaceflight venture that aims to send four private astronauts on a two-week trip to the International Space Station. Among the mission's crew are astronauts from India, Poland and Hungary who would be the first from their respective nations to ever reach the station.
Under the command of former NASA astronaut Peggy Whitson, the crew members are due to undertake about 60 scientific experiments during their time aboard the orbital laboratory. The research was developed specifically to take place in microgravity on behalf of organizations around the world, according to Axiom Space.
But the launch of the mission has undergone a slew of delays since Axiom Space was originally working toward a May 29 launch. When the crew does get off the ground, they'll be aboard a SpaceX Dragon capsule that will be propelled to orbit atop a Falcon 9 rocket launching from NASA's Kennedy Space Center in Florida.
The Axiom missions are also aimed at advancing the company's goals of building a space station that will attach to the ISS before its planned 2030 retirement. The missions began in 2022, with the most recent, Axiom Mission 3, taking place in January 2024.
This isn't the first time the International Space Station has experienced a leak.
In February 2024, an air leak in the Russian segment of the orbital laboratory known as the PrK module caused disagreement between Roscosmos and NASA about not only the cause, but how serious it was.
By November, the leak was still unresolved while the two space agencies were monitoring it. The area has also been sealed from the rest of the station when crew members did not need to access the spacecraft docked at the module.
Leaks of air from the cracks have been minor and posed no immediate safety threats to the station's astronauts, who patch the leaks with tape, glue and other solutions. But issues on the ISS are increasingly worrisome signs of aging.
In late-2024, a NASA Office of Inspector General report even raised concerns about whether it would be safe or even affordable to operate past the station's 2030 retirement date.
Seven members of Expedition 73, including three Americans, are living aboard the ISS – conducting scientific research and working to maintain the station.
That includes NASA astronauts Nichole Ayers and Anne McClain, who in May made headlines for completing a rare all-female spacewalk.
The women both arrived in March 2025 with JAXA astronaut Takuya Onishi and Roscosmos cosmonaut Kirill Peskov as part of a NASA mission known as Crew-10. That mission also made headlines due to its role in paving the way for the NASA astronauts who crewed the doomed Boeing Starliner to depart with the Crew-9 mission.
Also at the station is NASA astronaut Jonny Kim, who reached the outpost in April 2025 with cosmonauts Sergey Ryzhikov and Alexey Zubritsky.
Contributing: Reuters
This article originally appeared on USA TODAY: A portion of the space station is 'leaking.' Here's what that means.