Polaris Dawn, the private SpaceX mission currently orbiting Earth, has already set several records since its launch on 10 September. Hours after taking off, the mission’s Crew Dragon spacecraft reached an altitude of 1,400 kilometres, the highest orbit above Earth achieved by a crewed spacecraft and the farthest humans have travelled from Earth since NASA’s Apollo missions of the late 1960s and early 1970s. And earlier today, two of its crew, US entrepreneur Jared Isaacman and SpaceX engineer Sarah Gillis, completed the first-ever commercial spacewalk at a peak altitude of more than 700 kilometres.

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“Back at home, we all have a lot of work to do, but from here, Earth sure looks like a perfect world,” said Isaacman, as he stood with his head and torso poking out of the hatch of the spacecraft, preparing for his spacewalk manoeuvres.

Although these milestones are impressive, what is even more intriguing to researchers who spoke to Nature is what the mission could mean for the future of space science. With private citizens and flights going to space more frequently, there will be more opportunities to run experiments in microgravity and probe the bounds of human space travel.

“It’s probably the most exciting time in spaceflight since the 1960s,” says Christopher Mason, a geneticist at Weill Cornell Medical College in New York City, who leads the Space Omics and Medical Atlas (SOMA), a major repository for astronaut biomedical data. “Now we have spacesuits, spacecraft and a mission [that] are all from a private company, SpaceX, which is really the first time we’re having all of this independent organization of spaceflight.”

Space mechanics

Civilians being able to complete a spacewalk might even mean more options for fixing scientific equipment in space. In 2022, Isaacman proposed that NASA should use a crewed SpaceX mission to reboost the agency’s Hubble Space Telescope into a higher orbit to extend its lifetime. The telescope has been in space for 34 years and will gradually descend until it burns up in Earth’s atmosphere. NASA has turned down the proposal for now, citing the potentially catastrophic risks to both Hubble and the crew.

But with the success of today’s spacewalk — also known as an extravehicular activity, or EVA — the idea of a private company performing such difficult space operations has become that much more plausible. “If Polaris Dawn is completely successful with their commercial EVA, that will be one step forwards, and it might be that that’s enough to convince NASA,” says Laura Forczyk, executive director of the space-consulting firm Astralytical in Atlanta, Georgia.

In the meantime, Polaris Dawn will deliver scientific results after it splashes down in the coming days in either the Gulf of Mexico or the Atlantic Ocean. The mission’s Crew Dragon spacecraft, named Resilience, is carrying 36 experiments contributed by 31 different institutions across Canada, Saudi Arabia and the United States, many of them focused on the health of space travellers. “We stand to learn quite a bit,” said Isaacman during a press conference on 19 August. “If we get to Mars someday, we’d love to be able to come back and be healthy enough to tell people about it.”

More crews, more data

Polaris Dawn is the first of three planned Polaris missions funded and led by Isaacman, the chief executive of payment-processing firm Shift4, based in Center Valley, Pennsylvania. One of the goals of the Polaris programme is to help advance the human-spaceflight ambitions of Hawthorne, California-based firm SpaceX. The third Polaris mission will be the first crewed flight of SpaceX’s Starship, a fully reusable mega-rocket that NASA has enlisted to transport astronauts in several years to the Moon’s surface, as part of its ambitious Artemis programme.

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Before any of that, Polaris Dawn is testing some basics. For one, it debuted SpaceX’s EVA suit, the company’s first suit designed to protect humans from the vacuum of space. Gillis and Isaacman wore the suits during their spacewalk. “It’s not lost on us,” said Isaacman at the 19 August press conference, that “someday someone could be wearing a version” of the suit while walking on Mars.

For another, the mission is studying the health of the crew members on board. “Spaceflight is just a huge stressor,” says Jimmy Wu, the deputy director of the Baylor College of Medicine’s Translational Research Institute for Space Health (TRISH) in Houston, Texas, which collects medical data on commercial space travellers, including the Polaris Dawn crew.

Researchers think that private crewed spaceflights will help to get answers faster about how spaceflight affects health than government-led missions with trained astronauts, because they are lifting off more often. “It is really hard to study astronauts because it takes so long to get even 10 or 12 of them through six-month missions,” says Leigh Gabel, a kinesiologist at the University of Calgary in Canada, who studies the effects of microgravity on bone health. “Private space travel could give us a real leg up.”

How the body handles space

Gabel’s team will take high-resolution X-rays of the wrists and ankles of Polaris Dawn’s crew once they return to Earth, to measure the effects of several days’ worth of microgravity on bone structure. Her previous work on astronauts who have spent time on the International Space Station has shown that months of microgravity can cause the inner structure of load-bearing bones, such as those in the legs, to weaken in ways that don’t fully heal even one year after returning to Earth¹.

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Several researchers are also using Polaris Dawn to better understand spaceflight-associated neuro-ocular syndrome (SANS), a condition in which astronauts experience permanent changes — and even damage — to their vision. Scientists suspect that SANS stems from built-up fluid in the eye that would normally drain away in Earth’s gravity. Working with ophthalmologist Prem Subramanian and space-health researcher Allie Hayman at the University of Colorado Boulder, the Polaris Dawn crewmembers are each wearing a ‘smart’ contact lens that can record the fluid pressure in the eye.

Other researchers will be studying the effects of exposure to space radiation — high-energy charged particles — on the body by analysing DNA, RNA and other biosamples taken from the Polaris Dawn crew. Importantly, Polaris Dawn represents the first time that many of these analyses will be run on the same space traveller across two different missions: Isaacman also participated in SOMA and TRISH’s research when he commanded Inspiration4, an all-civilian orbital mission operated by SpaceX in 2021.

Isaacman is “one of the most well-characterized human beings that’s ever existed, actually”, Mason says. “He is the best chance we have to understand what happens to the body before you go to space, and then what happens every time you go to space.”