SpaceX has been sending its Dragon capsule on resupply missions to the International Space Station since 2012, when it became the first commercial ship to achieve such a feat. But the relationship isn't all one-way traffic, with the unmanned spacecraft also ferrying vital samples back to Earth for study by scientists here on the ground. Today, the Dragon capsule has splashed down in the Pacific Ocean, with heart cells and space mice hidden amongst its latest haul.

SpaceX's CRS-9 mission arrived at the International Space Station (ISS) on July 20 carrying 5,000 lb (2,270 kg) of supplies, equipment, and science experiments, along with the first of two new docking adapters that will be used by future commercial spacecraft currently under development.

The ISS crew sent the Dragon off on its return leg this morning after loading the capsule up with more than 3,000 lb (1,360 kg) of cargo. Among the important samples sent back to Earth were heart cells cultured aboard the ISS for one month as part of NASA's Heart Cells study.

What a month in space looks like(Credit: SpaceX Instagram)

This research focuses on how the microgravity environment affects the human heart, and how these impacts may vary from person to person. Deep space travel, like that required to reach Mars, will involve very lengthy periods of time in space exposing humans to a number of health risks, among which is the chance of atrophy of the heart muscle. These heart cells will now be studied for cellular and molecular changes with a view to better understanding heart disease and advancing drugs and cell replacement therapy to treat it.

The astro-mice that hitched a ride aboard the Dragon are a part of two separate studies, both aimed at learning how changes in mouse models might be indicative of how the human body will behave in future spaceflight missions. The Mouse Epigenetics study investigates changing gene expression patterns and DNA in the organs of male mice after one month in space, and also looks out for changes in the DNA of their offspring.

The SpaceX Dragon spacecraft as seen from the ISS on an earlier mission(Credit: NASA)

The Rodent Research-3-Eli Lilly study focuses on the rapid deterioration of bone and muscle mass in the legs and spine in space, and how this might be prevented. This involves comparing the effects to those experienced by humans with muscle-wasting conditions on Earth and testing an antibody that is known to prevent them in mice here on the ground.

Another set of samples to land this morning are a part of NASA's Multi-Omics experiment, which investigates the human immune system and how it reacts to the space environment and prebiotics, which are food ingredients designed to boost healthy bacteria in the intestines. The researchers do this by studying the composition of microbes in the digestive system, looking out for potential biomarkers that can be used to better manage astronaut health in space.

The Dragon spacecraft will be carried to a Los Angeles port by ship, where it will unload NASA's cargo before being carted off to SpaceX's test facility in Texas for processing.

Source: NASA

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