Whether it's Martians in War of the Worlds or a telekinetic visitor in E.T. the Extra-Terrestrial, science fiction is filled with aliens making their way to Earth.In science fact, though, there's greater concern that Earth-dwellers—specifically bacteria and microorganisms—could arrive at extraterrestrial destinations.
As NASA sends rovers to Mars, plans a trip to Jupiter's icy moon Europa, and looks for an ocean on Saturn's moon Enceladus, the hope is to find life-forms on those interstellar bodies. To ensure that doesn't include forms that originated on Earth—and that the new environment isn't compromised the way Earth ecosystems can be by invasive species or infectious diseases—NASA is now thoroughly cleaning its space-bound vessels.
The extreme heat of takeoff, the cold of space, and the speed of spacecraft are generally enough to kill bacteria and microorganisms. But scientists have discovered that a few hardy ones can stick around.
"A surprisingly large variety of organisms are able to survive a trip through space," says NASA Planetary Protection Officer Catharine Conley. "Experiments to put microbes, lichens, plant seeds, and even small animals on the outside of the International Space Station have demonstrated survival for years." . . .
