• When the Dragon spacecraft launched Tuesday atop a Falcon 9 rocket, the vehicle carried the private astronauts further into space than humans have reached in more than half a century.
• Two days after launching, the astronauts made further history: Becoming the first nonprofessional astronauts to open the hatch of their vehicle and expose themselves to the vacuum of space.

Last week, four commercial astronauts boarded a SpaceX capsule for a pioneering spaceflight that was years in the making.

For five days, the crew of the Polaris Dawn mission orbited Earth while completing a number of objectives that could one day bolster humanity's yearning to explore deep into the cosmos. Jointly funded by Elon Musk's SpaceX and billionaire Shift4 Payment CEO Jared Isaacman, the mission was one filled with historic moments – from the record heights the crew's spacecraft reached to the landmark spacewalk they were able to complete.

And though the astronauts landed safely Sunday off the coast of Florida, the overarching Polaris Program is just beginning with two more spaceflights ahead.

But for now, here's a look back at some of the major moments from the daring, history-defining Polaris Dawn mission.

SpaceX Dragon reaches historic heights

Prior to Polaris Dawn, Isaacman was the only member of the Polaris Dawn crew to have been to outer space before, having served in 2021 as mission commander of Inspiration4, the world’s first all-civilian mission to space.

Under his command was a crew that included pilot Scott “Kidd” Poteet, a retired United States Air Force lieutenant colonel who flew with the Thunderbirds; and mission specialists Sarah Gillis and Anna Menon, both lead space operations engineers at SpaceX.

When the Dragon spacecraft launched last week atop a Falcon 9 rocket, it wasn't long until the vehicle carried the private astronauts further into space than humans have reached in more than half a century.

Ascending to 870 miles above Earth's surface took the crew to a height higher than any crewed vehicle has traveled since NASA's Apollo era came to an end in the 1970s. The craft also surpassed the height reached by NASA's Gemini 11 in the 1960s, SpaceX said.

The ascent also marked the highest that the SpaceX Dragon has flown to date, SpaceX said in a day one update.

The milestone was one of the defining objectives of the mission, but it accomplished more than just earning the crew bragging rights.

Climbing to such a height – three times higher than the International Space Station – took the vehicle through the treacherous inner regions of Earth's Van Allen radiation belts. The region is one astronauts will have to traverse on future missions to the moon and Mars, and now SpaceX knows that its Dragon and its specially-designed spacesuits are capable of doing so.

For Menon and Gillis, they are now not only the the first SpaceX employees to travel to space, but have traveled higher than any other women in history.

Polaris Dawn astronauts conduct private spacewalk

The spacecraft didn't linger at the transcendent height, but eventually descended to a cruising altitude of 435 miles above Earth as the astronauts began preparing for what may have been the biggest test of the mission: Completing a spacewalk.

Two days into the mission, the Polaris Dawn crew members became the first non-professional astronauts to venture outside a spacecraft while in orbit.

The maneuver required extensive preparation to safely perform.

Shortly after liftoff, the Dragon's pressure began to slowly lower while oxygen levels inside the cabin increased, helping purge nitrogen from the crew members' bloodstreams and lower the risk of decompression sickness, SpaceX said.

By Thursday morning, the crew donned extravehicular activity (EVA) suits designed by SpaceX, completed suit leak checks and vented the Dragon to match the vacuum of space. Because the Dragon does not have an airlock, the entire cabin was depressurized and all four astronauts were suited up in the EVA suits to receive oxygen through tethers.

By around 8 a.m. EDT, Isaacman and Gillis exited the Dragon capsule separately for about 10 minutes each to take in the endless black expanse of outer space while tethered and holding onto handrails. The spacewalk was intended to test the capabilities and mobility of SpaceX's new suits, which the company designed to protect astronauts against radiation and extreme temperatures.

Poteet and Menon remained strapped in their seats monitoring vital support systems. But because all four crewmembers were exposed to the vacuum of space, they are all considered to be part of the first-ever spacewalk conducted by anyone other than government astronauts.

"Back at home we all have a lot of work to do, but from here Earth sure looks like a perfect world," Isaacman said as he emerged from the hatch. In response, SpaceX ground crews in Hawthorne, California could be heard on a livestream bursting into applause.

Anna Menon reads children's book from orbit, Sarah Gillis plays violin

The mission may be one for the history books, but it was filled with some personal moments as well.

Along the way, mission specialist Anna Menon took time to read from orbit a children's book she co-authored to her two kids back on Earth. Menon's son and daughter tuned in for the virtual book reading, as did some youngsters at at St. Jude Children’s Research Hospital.

Menon, also the medical officer for the spaceflight, was inspired to write "Kisses from Space" while training for the Polaris Dawn mission as a way to stay connected with her children. The story is one of a mother dragon who returns home after an out-of-this-world adventure to regale her children with tails of her exploits.

Menon co-authored the book with her cousin Keri Vasek, while award-winning illustrator Andy Harkness created the visuals for "Kisses from Space," which was published June 4.

Gillis, a classically trained violinist, also had the opportunity to record herself performing music from "Star Wars" on her violin, accompanied by students from El Sistema, which provides music education.

Crew members test Starlink, conduct 40 scientific tests

The entirety of the mission represented a new chapter of space exploration as companies like SpaceX increasingly seek to conduct ventures that were once almost exclusively the realm of space agencies like NASA.

Along the journey, the crew tested a new laser-based satellite communication system using Starlink by making multiple calls to Earth. They also conducted nearly 40 scientific experiments – many of which aimed to understand the human body's reaction to long spaceflights as NASA and other space agencies set their sights on destinations like Mars.

The first of three missions under the Polaris Program, the venture could set the stage to one day make SpaceX founder Elon Musk's vision of crewed trips to Mars a reality.

The second mission "will continue to expand the boundaries of future human spaceflight missions, in-space communications, and scientific research," according to the program's website. Additional details, including a launch date, have not yet been announced.

When the day comes that the third and final Polaris Program mission launches, it's intended to be the first human spaceflight on the SpaceX Starship rocket. The gargantuan rocket, which has so far only undergone uncrewed tests, will one day ferry NASA astronauts from lunar orbit to the moon's surface as part of the space agency's Artemis program.

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at [email protected]