Slide 1 of 14
Space Plane ScienceThe chief science legacy of NASA's space shuttle program may be the International Space Station, the gigantic orbiting lab that shuttle missions helped build over the past 13 years. But lots of interesting research has also been done aboard the shuttles themselves since they started flying in 1981.
Long before the station was up and running, space shuttle missions broke new ground in many different fields of research, taking advantage of the microgravity environment to perform studies that couldn't be done on terra firma.
As the last-ever shuttle launch nears — NASA's STS-135 mission aboard Atlantis will blast off July 8 — here's an admittedly subjective countdown at six of the coolest experiments ever done aboard NASA's iconic space plane.
Zero-G Microbes are NastierSlide 2 of 14
Zero-G Microbes are NastierExperiments aboard the space shuttle have shown that Salmonella bacteria, a common and sometimes deadly source of food poisoning, get more virulent in space. [9 Weird Things Flown On NASA's Space Shuttles]
Researchers first noticed this characteristic in studies performed aboard Atlantis' STS-115 flight in 2006 and the STS-123 mission of Endeavour two years later. And it's not a subtle change; Salmonella becomes three to seven times more virulent in microgravity conditions, researchers have said.
Scientists believe that the bacteria get ramped up because spaceflight tricks them into behaving as if they're inside the human gut. The shuttle missions also identified dozens of genes that seem to be involved in the hyper-virulence, as well as a "master switch" protein that regulates many of these genes.
The biotech firm Astrogenetix worked with NASA to conduct and extend this research, and the company recently developed a Salmonella vaccine based on it. Astrogenetix is also performing space-based studies of other pathogens, such as dangerous methicillin-resistant Staphylococcus aureus (MRSA) bacteria, with the aim of finding better treatments down the road.Slide 3 of 14
13-Mile Space Tether TryoutSlide 4 of 14
13-Mile Space Tether TryoutThe experiment, called the Tethered Satellite System (TSS), was a joint effort between NASA and the Italian space agency. The idea was to show that tethered satellites could generate electric current as they cruised through Earth's magnetic field.
During STS-46, the tether unspooled just 840 feet (256 meters) from Atlantis before the reel jammed. Four years later, 12.2 miles (19.7 km) of cable were released before the 0.1-inch (0.25 centimeter) tether snapped, sending the probe shooting away into a higher orbit.
Though neither attempt was 100 percent successful, the TSS belongs on this list for its scale and ambition alone. And the 1996 experiment did return some interesting results. Before the tether snapped, the TSS had been generating 3,500 volts and up to 0.5 amps of current, according to NASA officials.Slide 5 of 14
Smelling the Space RosesSlide 6 of 14
Smelling the Space RosesIt sounds like some sort of symbolic or ceremonial gesture: The shuttle Discovery carried a single rose to orbit on its STS-95 mission in 1998.
But there was science, and business, behind the move. The company International Flavors and Fragrances (IFF) wanted to see how microgravity altered the sweet and familiar scent of a rose — and if a new perfume component might come out of the experiment.
So IFF sent a miniature rose plant up, and shuttle astronauts sampled its volatile oils, which carry the essential odors of the flower. It turned out that the space rose produced fewer volalites than its counterparts did back on Earth. And, more importantly, its overall fragrance was entirely different.
IFF commercialized the space rose odor, which has since been incorporated into "Zen," a perfume put out by the company Shiseido Cosmetics. NASA flew another rose on a space shuttle in 2007, but that flower was destined for the annual New Year's Rose Parade in Pasadena, Calif., not a perfume.Slide 7 of 14
Bigger, Better Protein CrystalsSlide 8 of 14