More than one thousand tubes of blood, urine, and saliva made their way back to Earth from the International Space Station aboard the SpaceX-8 Dragon capsule, signaling an exciting next step for the scientists leading research for the recently completed One Year Mission. NASA astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko returned to Earth from their yearlong mission aboard the orbiting laboratory more than two months ago, but many of the samples critical to the continuation of research have only just made their way back to labs this week.

"[It's] like Christmas in May, with frost to boot," said Scott M. Smith, who holds a doctorate in nutrition and is a principal investigator of the Biochemical Profile investigation.

Smith was referring to the specialized cold stowage needed to safely transport temperature-sensitive samples. After being collected in space, crew members store the samples in the Minus Eighty-Degree Laboratory Freezer for ISS (MELFI). The tubes are transferred to either powered freezers or insulated coolers with special ice packs which are then packed inside the SpaceX Dragon capsule to be returned to Earth.

"SpaceX provides our primary capability for sample return, allowing us to bring home freezer bags and powered freezers containing samples," said chief scientist for the space station, Julie Robinson, who holds a doctorate in Biology.

After splashing down in the Pacific Ocean, the Dragon capsule was loaded onto a ship and taken to shore in Long Beach, California. Members of NASA's Johnson Space Center (JSC) Cold Stowage team transferred the samples to a charter aircraft, where portable, powered freezers awaited. While some investigators were on hand in California to retrieve their samples directly from the Cold Stowage team aboard the aircraft, most of the precious cargo was flown back to Houston for distribution at JSC.

"Samples coming home on Space-X include samples from a variety of human experiments," said Robinson. "Most notably blood, urine and saliva collected from the crew for the One-Year Mission and Twins Study."

Studies supported by the samples coming back in this batch include Biochemical Profile, Cardio Ox, Fluid Shifts, Microbiome, Salivary Markers and the Twins Study. A point of contact for each study was on hand to receive the samples from JSC's Cold Stowage team.

"The inventory process is actually pretty intense," said Smith.

Members of the Cold Stowage team hand samples off to researchers, who are assigned time slots for retrieving their precious cargo.

"We inventory and check every tube serial number against what we expected," said Smith. "Once we have all of [our samples], and are sure we don't have anything we're not supposed to, official documents are signed, and we bag them up to carry back to the lab."

Once back in their lab, also onsite at JSC, Smith's team will unpack and re-inventory everything once again, to ensure nothing was lost in the dry ice or during the return to the Nutritional Biochemistry Lab. From there, the samples will be packed in laboratory minus eighty-degree freezers until further preparation for analysis.

Stuart Lee, who holds a doctorate in Kinesiology, and is the principal investigator for the Cardio Ox and Cardio Ox Twins investigations, said many of the samples will be shared between his and Smith's biochemical profiles investigation. Lee said that seven subjects have completed their mission for cardio ox, but samples for only three of those have been previously returned to Earth.

"Given that, we will more than double the amount of data that we have for Cardio Ox with this sample return," said Lee. "Of course, we also get the excitement of starting to receive the data from the One-Year Mission."

Lee said that up until now, scientists' data have described the effects of spaceflight from the typical six-month missions to the space station, but data from the One-Year Mission samples will change that.

"This will be NASA's first glimpse at the effects of space travel which start to approach that which we might expect from a Mars mission," said Lee. "These data may provide clues as to whether we can expect more, or more extreme, changes as mission duration increases."

Samples for the Twins Study, in which Kelly and his identical twin brother, retired NASA astronaut Mark Kelly, participated, also returned on SpaceX-8. The blood and urine components of those studies offer new molecular analyses for investigators.

"With these samples," said Lee. "we will have pilot data to understand spaceflight effects on and linkages between genetic expression, protein expression, and physiology, improving our understanding of the cardiovascular system in space as well as astronauts' ophthalmologic issues."

This batch of samples includes the final collection returning from space for the One-Year Mission investigations. While some of the investigations include several data collections in the year - or longer - beyond the crew's return to Earth, analysis of the returning samples can begin, in most cases, when they reach the scientists' laboratories. The Twins Study investigators have agreed to wait until after the return plus six-month data collection completes in September 2016, Smith said.

Smith said organization, tracking and careful planning is critical to successful analysis. Thought has to be given to samples that can only be thawed one time, and samples that need to be run at the same time as those collected before and after flight, to reduce variability.

"We analyze over 100 chemicals in each blood sample, and over 30 in each urine sample," said Smith. "We try to have samples available for the folks analyzing them as quickly as possible. Nonetheless, depending on the type of test, and number of samples - it can take quite a bit of time."

With samples being delivered to investigators across the country, Smith remains optimistic that the bulk of testing on these samples will be completed by the end of the year.

"[The research is] very carefully plotted out and planned, reviewed, documented and then executed," said Smith. "We only get one shot at this."