USA TODAY NETWORK The fours astronauts of Axiom Mission 4 splashed down in the early hours of Tuesday, July 15 in the Pacific Ocean aboard the same SpaceX Dragon capsule they rode to the ISS. Under the command of retired NASA astronaut Peggy Whitson, the crew spent more than two weeks conducting about 60 scientific experiments. The first SpaceX mission to end with a splashdown in California was the Fram2 mission in April. Four commercial astronauts from different nations have returned to Earth on a SpaceX vehicle that became the latest spacecraft returning from orbit to make a splashdown off the coast of California. The West Coast water landing comes after NASA and SpaceX recently moved spaceflight recovery operations from Florida, where crewed missions get off the ground. The crew members of a private venture known as Axiom Mission 4 splashed down in the early hours of Tuesday, July 15, in the Pacific Ocean aboard the same SpaceX Dragon capsule they rode more than two weeks ago to the International Space Station. The mission was the latest spaceflight led by Texas-based Axiom Space, which partnered with both NASA and SpaceX – the commercial spaceflight company founded by billionaire Elon Musk. The mission, also known as Ax-4, represented the fourth time in about three years the company has sent a crew to the space station for a private research mission. The four astronauts selected from the mission, who exited the Dragon after a SpaceX team hoisted it on a recovery vessel, are now due to receive standard medical evaluations, an Axiom Space spokeswoman told the USA TODAY Network. Here's what to know about the Axiom 4 mission, as well as the crew's return to Earth. SpaceX Dragon makes splashdown off California coast The SpaceX Dragon, with the four spacefarers aboard, made a parachute-assisted water landing at 2:31 a.m. PT Tuesday, July 15, off the coast of California, according to Axiom Space. The splashdown came nearly 22 hours after the Ax-4 crew boarded the capsule to undock at 7:15 a.m. ET Monday, July 14, from the International Space Station. The departure and subsequent return to Earth marks the end of a mission that got off the ground Wednesday, June 25, from NASA's historic Launch Complex 39A at Kennedy Space Center near Cape Canaveral following a series of launch delays. All told, the astronauts spent 20 days in space, including 18 on the station conducting research and assisting Expedition 73 in station maintenance. What was the Axiom 4 mission? Under the command of retired NASA astronaut Peggy Whitson, the crew spent more than two weeks conducting about 60 scientific experiments developed to take place in microgravity on behalf of organizations around the world, according to Axiom Space. Whitson, director of human spaceflight at Axiom Space, commanded a crew that included Shubhanshu Shukla of the Indian Space Research Organization (ISRO), Sławosz Uznański-Wiśniewski of Poland and Tibor Kapu of Hungary. Shukla, Uznański-Wiśniewski and Kapu were all the first from their respective nations to ever reach the space station. Most recently, the Ax-4 astronauts spent time ahead of their return voyage collecting blood samples for biomedical research, studying microalgae as a food resource for crews in space and testing fabrics for future spaceflight gear. The Dragon spacecraft made its way back to Earth with more than 580 pounds of cargo, including NASA hardware and data from the experiments the astronauts conducted throughout the mission. "This mission reflects Axiom Space’s vision of a thriving low-Earth orbit economy, where access to space is no longer limited to a few, but extends to all who seek to explore, discover, and innovate," Tejpaul Bhatia, CEO of Axiom Space, said in a statement. What is the SpaceX Dragon? The SpaceX Dragon is the only U.S. vehicle capable of transporting astronauts to and from the space station. The spacecraft recently found itself at the center of controversy when billionaire Elon Musk, the founder of SpaceX, threatened to decommission the Dragon following threats from President Donald Trump to end government contracts with the commercial spaceflight company. Musk later backed down on the idea. Standing nearly 27 feet tall and about 13 feet wide, the Dragon is also one of four cargo spacecraft that deliver science experiments and other cargo to the space station on a regular basis. Dragon capsules can also carry up to seven astronauts into orbit, though most of SpaceX's Crew missions, which are contracted with NASA, feature a contingent of four.