SpaceX Dragon returns home loaded with scientific experiments

The SpaceX commercial cargo ship Dragon returned to Earth from the International Space Station on Sunday, bringing back nearly 2 tons of science experiments and old equipment for NASA. It splashed down into the Pacific, just five hours after leaving the station.

"Splashdown is confirmed!! Welcome home, Dragon!" SpaceX tweeted, sending along a photo of the cargo ship in the Pacific Ocean.

The Dragon rocketed to the space station on April 18 with a full load of cargo and arrived at the orbiting lab two days later. After a one-month visit, astronaut Steven Swanson, the station commander, released it Sunday using the big robot arm as the craft zoomed more than 260 miles above Earth.

"Very nice to have a vehicle that can take your science, equipment and maybe someday even humans back to Earth," Swanson told Mission Control.

SpaceX's Dragon is the only commercial supply ship capable of returning items to Earth; others are designed to burn up on re-entry. This was the fourth Dragon to bring back space station goods.

Its payload included about 1,600 pounds of science cargo from the space station, including 150 science experiments, NASA officials said in an statement. The experiments include samples from biology, biotech and physical science investigations, as well as human research.

"While some of this data can be obtained by on orbit analysis, many analysis techniques have not been miniaturized or modified to allow them to be performed on orbit, which means sample return is the only way to obtain this data," Marybeth Edeen, space station research integration office deputy manager at the Johnson Space Center in Houston, said in the statement.

One such experiment involved the effects of space and microgravity on the growth of E. coli bacteria. Previous studies showed that bacteria are able to grow in space, even with drug concentrations that would be effective on earth. As bacteria grow more resistant to antibiotics, scientists hope to use the data from this experiment to improve antibiotic development.

Another experiment involved Micro7, the first space investigation to study the effects of microgravity on DNA damage and repair fibroblasts -- the non-dividing cells that make up most of the human body. Eventually, scientists hope to be able to develop new drug therapies with this data as well.

In addition to California-based SpaceX, Russia, Europe and Japan also make occasional shipments to the International Space Station. Another American company, Orbital Sciences Corp., will be launching a cargo ship to to the space station next month.

SpaceX also is competing for the right to ferry station astronauts as early as 2017.