When diseases like SARS, Mad Cow Disease and Monkeypox cross the species barrier and infect humans, they dominate news headlines. Just imagine, then, the reaction if potentially infectious pathogens were found in rock samples from Mars. As we look toward exploring other worlds, and perhaps even bringing samples back to Earth for testing, astrobiologists have to wonder: could alien pathogens cross the "planet" barrier and wreak havoc on our world? Even though there is no proof of bacterial or viral pathogens anywhere except Earth, there is already a worried advocacy group called the International Committee Against Martian Sample Return, and science fiction novels like "The Andromeda Strain" depict nightmare alien infection scenarios. The possibility of cross-planetary contamination has concerned NASA since the early days of the Apollo program, so, as a precaution, the astronauts were quarantined for three weeks after they left the moon. Chris Chyba, who holds the Carl Sagan Chair for the Study of Life in the Universe at the SETI Institute, says there are two types of potential alien pathogens: toxic and infectious. Toxic pathogens act as a poison on other organisms. Infectious pathogens are viruses or bacteria that are passed between organisms, causing sickness. Some viruses and microbes rely on specific biological systems in order to replicate and infect their host, so not all pathogens affect all organisms the same way. Chicken farmers, for instance, can remain untouched by a disease that decimates their flocks. It could be that a martian microbe would enter the human body, but is rendered harmless because it is incompatible with human physiology. "After living in the dirt of Mars, a pathogen could see our bodies as a comparable host; they could treat us 'like dirt,'" says John Rummel, NASA's Planetary Protection Officer. "But, to quote Donald Rumsfeld, we're dealing with the unknown unknowns. It could be that even if the microbes lived inside us, they wouldn't do anything, it would just be this lump living inside you."
View: Full Article | Source: AstroBiology Magazine
