(AP) -- After eight days together, it's time for the space shuttle and space station crews to say goodbye.
The hatches between the linked spacecraft will be sealed early Wednesday afternoon. Three hours later, Discovery will undock.
Discovery will be bringing back five months' worth of science experiments from the space station. The blood, urine and saliva samples need to be kept cold for as long as possible, and will remain in the station freezer until the last possible moment.
The shuttle also is bringing back four to five liters of recycled water made from astronauts' urine and condensation. NASA wants to make sure the water is safe before space station astronauts start drinking it up there.
Discovery and its crew of seven are due back in Florida on Saturday.
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