The SpaceX Dragon capsule returned to Earth on Tuesday with a full science load from the International Space Station.

The privately owned cargo ship splashed down in the Pacific, off the coast of Mexico's Baja Peninsula, five hours after leaving the orbiting lab. The California-based SpaceX confirmed the Dragon's safe arrival via Twitter.

"Special delivery! Dragon now being recovered in the Pacific," the company said in a tweet.

The capsule brought back more than 1 ton of science experiments and old station equipment. It's the only supply ship capable of two-way delivery. NASA is paying SpaceX more than $1 billion for a dozen resupply missions.

The unmanned capsule will be shipped to Los Angeles arriving Wednesday night and then trucked to Texas for unloading.

Earlier in the day, astronauts released the unmanned capsule from the end of the space station's giant Canadarm2 robot arm. The 400-kilometre-high parting was a poignant moment for the three space station's residents, who helped to snare the Dragon three weeks earlier.

"Sad to see the Dragon go," astronaut Thomas Marshburn told Mission Control. "Performed her job beautifully. Heading back to her lair. Wish her all the best for the splashdown today."

The Dragon used old-NASA-style parachutes to plop into the ocean; company officials indicated all appeared to go well during the re-entry.

SpaceX launched the capsule from Cape Canaveral at the beginning of March. Mechanical trouble caused a one-day postponement in Dragon's arrival at the space station. SpaceX flight controllers at company headquarters in Hawthorne, Calif., managed to fix the problem within hours.

Bad weather at mission's end in the Pacific recovery zone kept it in orbit an extra day.

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Private space cargo ship returns from space station