SpaceX's Dragon cargo capsule left the International Space Station today after a month-long stay at the orbiting lab. The spacecraft undocked from the ISS earlier this morning and splashed down in the Pacific Ocean around 2:51PM ET, according to SpaceX.

This particular spacecraft carried extra special cargo back to Earth: biological samples from former NASA astronaut Scott Kelly. Kelly recently stayed on the ISS for 340 days to help researchers better understand what happens to the human body during long-term spaceflight. His samples, collected during his stay on the ISS, will provide a snapshot of the body changes Kelly went through.

Scott Kelly's biological samples were onboard

On Monday and Tuesday, astronauts onboard the ISS packed up the Dragon with more than 3,700 pounds of supplies, including Kelly's bodily fluids and other samples that will be used for biotechnology research, physical science research, and more. NASA then started the Dragon's undocking process earlier this morning; the station's Canadian robotic arm detached the spacecraft from the ISS, in order to move the capsule far enough away from the station. At 9:18AM ET, ESA astronaut Tim Peake released the Dragon from the arm, and the capsule fired its onboard thrusters three times to take it farther away from the station.

Afterward, the Dragon took itself out of orbit around 2PM ET and then plummeted back down to Earth. Unlike Orbital ATK's expendable Cygnus capsule, the Dragon is designed to survive the descent through Earth's atmosphere. Parachutes helped to slow the capsule during its fall, allowing it to touch down gently in the Pacific Ocean. Eventually, SpaceX hopes to land the crewed version of its Dragon by reigniting engines onboard the capsule, to perform a controlled landing on solid ground. It's how SpaceX intends to land Dragons on Mars in 2018. But the company has yet to land a capsule this way.

Now, a ship will transport the returned Dragon to Long Beach, California, where the capsule's cargo will be taken out. The Dragon will eventually be taken back to SpaceX's testing facility in McGregor, Texas, according to NASA.

Update May 11th, 3:19PM ET: The article has been updated to confirm that the Dragon splashed down successfully in the ocean.

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