WASHINGTON, Jan. 13 (Xinhua) -- SpaceX's upgraded Dragon cargo spacecraft splashed down at 8:26 p.m. East Time Wednesday (0126 GMT Thursday) off the Florida coast, completing the company's 21st contracted cargo resupply mission to the International Space Station (ISS) for NASA.

The spacecraft carried more than 4,400 pounds (about 1,996 kg) of valuable scientific experiments and other cargo back to Earth.

The upgraded Dragon cargo undocked from the ISS on Tuesday. It is the first undocking of a U.S. commercial cargo craft from the International Docking Adapter on the station's space-facing port of the Harmony module.

Previous cargo Dragon spacecraft was attached to and removed from the ISS using the station's robotic Canadarm2, according to NASA.

This upgraded Dragon cargo transported significantly more science back to Earth than possible in previous Dragon capsules, and is the first space station cargo capsule to splash down off the coast of Florida, according to NASA.

In addition, it is the first time science returned from the ISS through NASA's Kennedy Space Center in Florida since the retirement of the space shuttle.

Splashing down off the coast of Florida enables quick transportation of the science aboard the capsule to Kennedy Space Center's Space Station Processing Facility, according to NASA.

Dragon cargo was launched on Dec. 6 last year on a SpaceX Falcon 9 rocket from Kennedy Space Center, arriving at the ISS just over 24 hours later and achieving the first autonomous docking of a U.S. commercial cargo resupply spacecraft.

The spacecraft delivered more than 6,400 pounds of hardware, research investigations and crew supplies.