Expedition 4 Flight Engineer Carl Walz collected the final plant and gas samples during the week of April 1, 2002, before the ADVASC-GC-02 unit was deactivated on Sunday, April 7. The growth chamber will be returned on the Shuttle Atlantis (STS-110), which docked with the Station on April 10. The support system will remain on the Station in anticipation of the arrival of ADVASC-GC-03 during mission UF2 later this year. Activated on February 12, ADVASC-GC-02 had seedlings growing in it by early March. The growth chamber contains Arabidopsis seeds produced during ADVASC's first flight (ADVASC-GC-01). "This will be second-generation Arabidopsis plants produced from the seeds produced by those first-generation space-grown plants," described Dr. Weijia Zhou, principal investigator for ADVASC and director of the Wisconsin Center for Space Automation and Robotics (WCSAR) at the University of Wisconsin, Madison. "Additionally, we are going to sample the plant tissue and preserve it for RNA and DNA analysis after returning to the ground. Hopefully it will provide important information regarding the impact of low gravity on the plant gene expression."
ADVASC-GC-01, activated on May 10, 2001, was the first experiment on Station to return data to ground centers via video. By the week of May 28, the seeds had sprouted. The research team reported that the seedlings appeared on the video to be slightly larger than expected. The plants began to flower during the week of June 11 and had produced seeds within two weeks. During the first week of July, Increment 2 Flight Engineer Jim Voss had raised the heat and removed nutrients, fluids, and gases from ADVASC unit in order to dry out the plants and preserve them for their return to Earth.
The unit, plants, and samples were returned to Earth by STS-104 on July 24, and sent to WCSAR. Approximately 90 percent of the seeds sent into space germinated. Of those, about 70 percent grew siliques (elongated, two-sided seed capsules characteristic of the mustard family), with an average of 24 siliques containing 36 seeds per plant. WCSAR researchers are also comparing the space-grown plants to a control group grown under similar conditions on the ground. Part of the analysis also includes determining cell wall and chemical composition. Differences between the ADVASC plants and the ground-control plants will likely be due to the microgravity environment. The overall health and vigor of the space-grown plants will tell researchers whether the growing conditions—temperature, moisture, and fertilizer concentrations—were optimal. Some of the seeds are currently being grown in ADVASC-GC-02, but most of the seeds were turned over to Space Explorers, Inc., for use in their educational kits and other commercial endeavors.
Long-term plant research may allow crews on long-duration space flights to successfully grow and nourish their own crops. Plants also provide a natural air and water filtration system. From the humble beginnings represented by ADVASC may come advanced, large-scale plant growth systems for spacecraft. Space horticulture is the cornerstone of a healthy, enclosed life support system for future human space exploration. Furthermore, plant growth systems provide a little piece of Earth that helps make the spacecraft environment feel more like home.
Finding the key to growing crops in space - a challenging growing environment—may also improve crop yields on Earth by helping scientists to genetically tailor plants that will withstand disease and inhospitable conditions, and will require less growing space.
Components of the ADVASC system have yielded some surprising benefits. Homeland defense has been on the minds of many Americans since September 11, but few would have expected that a safety device would come from a plant growth chamber orbiting Earth. Ethylene is a natural byproduct of growing plants, but too much of this gas can build up in a growth chamber, causing plants to mature before they have had a chance to properly produce fruit and seeds. Researchers at WCSAR invented Bio-KES, a device that uses ultraviolet lights to convert ethylene into carbon dioxide and water, to remove ethylene from growth chambers like ADVASC. Scientists at the University of Wisconsin discovered by increasing the intensity of the ultraviolet lighting, they could use Bio-KES technology to kill pathogens like anthrax. The air scrubber, named AiroCide TiO2, is now being manufactured by KES Science & Technology, Inc., of Kennesaw, GA. For more on this space research spin-off, please visit the NASA News Release.
Researchers have also found that the light used for photosynthesis in ADVASC heals wounds and improves the effectiveness of cancer-fighting drugs. The light-emitting diodes (LEDs) developed for WCSAR by Quantum Devices, Inc., have been successfully used in surgical devices that remove tumors. Cooler than a laser, these LEDs can target diseased tissue without harming the surrounding healthy tissue.
Additionally, ADVASC provides an active link between science conducted onboard the ISS and the education community. Space Explorers, Inc., commercial partner on the ADVASC experiment, has developed Orbital Laboratory, an Internet-based, multimedia educational tool that allows students (grades K-12) to conduct experiments on the ISS and to analyze returned data. Students will be able to access ADVASC plant data and discuss data gathered by other participating schools worldwide. Space Explorers, Inc., and InnerLink, Inc., have developed the Orbital Laboratory Payload 002 Innerlinkit, a commercially available kit that contains supplies necessary to participate in the ADVASC experiment and a one-year subscription to the Orbital Laboratory Web site.