A trio of science payloads have completed their missions on the International Space Station and returned to NASA's Kennedy Space Center in Florida, where they'll be turned over to the scientists who designed them.

The BRIC-18, Biotube-MICRo and APEX-02-2 investigations were created to answer a variety of biological questions critical to future long duration spaceflight, from the prevention and treatment of antibiotic-resistant bacterial infections to several mysterious aspects of plant growth.

The payloads were launched to the station by SpaceX's Falcon 9 rocket and Dragon spacecraft, which lifted off from Florida's Cape Canaveral Air Force Station on April 18. SpaceX-3 was the third flight to deliver cargo to the orbiting complex under the company's Commercial Resupply Services contract with NASA.

Dragon berthed to the space station April 20. Over the next few days, the station's crew members carefully removed the science payloads from the capsule-shaped spacecraft and brought them aboard for the experiments to begin.

Throughout the flight, payload development teams in the International Space Station Ground Processing and Research Project Office at Kennedy tracked the studies' progress from a small control room in the Space Station Processing Facility called the Experiment Monitoring Area (EMA). From their EMA consoles, members of each payload team could answer questions or offer any necessary guidance while the astronauts were manipulating the payload.

Biotube-Magnetophoretically Induced Curvature in Roots, or Biotube-MICRo, was developed by the University of Louisiana, Lafayette, to study how magnetic fields and gravity affect the direction of plant growth. The payload contained three magnetic field chambers carrying small cassettes holding seeds of the fast-growing Brassica rapa plant.

The Biotube-MICRo payload was placed in an EXPRESS Rack, a standardized unit for storing and supporting experiments on the space station. NASA's Marshall Space Flight Center in Huntsville, Alabama, then sent the command to apply power to the rack, which in turn powered the experiment.

"At that time, we sent the command from the ground here at Kennedy to begin the experiment," explained Ralph Fritsche, the study's payload manager.

An automated process injected water into the cassettes to start the seeds growing. After 18 hours, video from the station showed a sufficient amount of plant and root growth. A fixative then was injected into the cassettes that ended the experiment.

Biological Research in Canisters-18, or BRIC-18, included two separate studies housed in a total of four unpowered bread-box-sized containers holding petri dishes. BRIC-18-1 was developed by the University of Florida in Gainesville to capture the effects of spaceflight on two common bacteria, Bacillus subtilis and Staphylococcus epidermidis.

BRIC-18-2, designed by the Michigan State University in East Lansing, Mich., looked at how plants deal with the stresses of life in space, from vibrations of launch to lack of gravity.

The canisters in the BRIC-18-1 study grew for five days, then moved into the station's minus eighty-degree freezer. The temperatures in the cold-storage unit halted biological processes and preserved the bacteria.

Half of the Arabidopsis thaliana plant seedlings in BRIC-18-2 grew for seven days, then the crew injected the samples with a fixative. The other half of the seedlings were permitted to grow for an additional week before the fixative was applied.

"Everything went exactly as planned," said BRIC-18's payload manager, David Flowers.

Temperature loggers installed on the payload kept track of the temperatures samples faced during the course of the experiments. This information will allow the payload team to replicate these conditions during upcoming control experiments that will be conducted in a Kennedy laboratory.

Spaceflight does occasionally present challenges. The payload and science teams for the Advanced Plant Experiments investigation, APEX-02-2, faced such an unexpected obstacle.

APEX-02-2 was developed by the U.S. Department of Veteran's Affairs; Duke University School of Medicine; and the University of British Columbia, Canada. The experiment contained 10 plates colonized with yeast. The experiment originally was intended to track changes in the samples' gene expression in the microgravity environment, as well as the radiation effects they encountered in flight.

But the plate reader required to capture the gene expression malfunctioned after only five hours of data were recorded, explained payload manager Jose Camacho. The teams met quickly to devise a workaround to complete as much of the study as possible.

"We coordinated a plan to get all the plates moved into the Commercial Generic Bioprocessing Apparatus," Camacho said. "This allowed the radiation assessment portion of the experiment to continue."

"All the teams did a great job responding to the problem and quickly putting a workaround in place. We're still expecting great science," Camacho added.

All three payloads returned to Earth when Dragon splashed down in the Pacific Ocean on May 18 after nearly a month at the space station. After a brief stop at NASA's Johnson Space Center in Houston, the APEX-02-2, Biotube-MICRo and BRIC-18 payloads arrived at Kennedy on May 22.

Now safely back where their journey began, the specimens in each study will be removed from the payload hardware and handed over to their respective science teams for analysis.