Another subset of SLS-1 investigations focused on the brain, nervous system, eyes and inner ear and included experiments from a joint US/Canadian project to investigate the impact of space sickness on the performance of the crew. One intriguing piece of hardware involved an astronaut placing his or her head inside a rotating dome, which induced a sense of self-rotation in the direction opposite that of the dome's own rotation. The subject then used a joystick to indicate his or her perception of self-motion.
Awareness of position in space is important, particularly during re-entry and landing when astronauts need to reach levers and switches. The general results of the SLS-1 motion experiments pointed to a loss of sense of orientation and limb position in the absence of visual cues. On several occasions, astronauts were also blindfolded and asked to describe the position of their limbs in reference to their torsos and point towards familiar structures within the Spacelab. Other experiments investigated changes in the inner ear, which has long been known to be highly sensitive to gravity and responsible for causing disorientation in space.
The nervous-system experiments, meanwhile, involved the first-ever flight of jellyfish on board the Shuttle: 2,478 moon jellyfish (Aurelia aurita), to be precise, which were housed in two containers in one of Columbia's middeck lockers. These were chosen because they are one of the simplest organisms known to possess a nervous system; they employ structures known as 'rhopalia' to maintain their correct orientation in water, akin to mammalian otoliths. The main aim of the jellyfish experiment was to determine their reproductive abilities and the impact of microgravity on their gravity-sensing organs and swimming behaviour.
The jellyfish were videotaped throughout the mission and finally 'fixed' on 12 June to preserve them for their return to Earth. Overall, the jellyfish polyps, which developed into sexually reproductive ephyrae in space, proved 'normal' in most respects, although they did exhibit hormonal changes and abnormalities in their swimming behaviour after landing. Differences were also noted in the gravity-sensing organs of terrestrial-born jellyfish, compared to their space-born counterparts.
While this work was underway in the Spacelab, 12 GAS canisters conducted their own research on a bridge at the rear of Columbia's payload bay. This structure was identical to that flown on STS-61C in January 1986 and its experiments included a European-built accelerometer so sensitive to movement that it could only be turned on while the astronauts were asleep. Others grew gallium arsenide crystals - some up to 9 cm long - that might prove useful in high-speed semiconductors for solar cells, produced harder-wearing, 'hollow' ball bearings, experimentally soldered metals and studied atomic oxygen effects on flower and vegetable seeds.
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