In the ongoing quest for extraterrestrial life, imagine the day scientists discover life on another planet. Then imagine finding out that those life forms actually originated on Earth.
With every spacecraft that leaves Earth, millions of microbes try to hitch a ride into outer space. NASA hopes to launch a Mars Sample Return Mission in the future, and preventing cross-contamination of Mars and the Earth in such a mission would be a top priority.? See: Earth microbes elsewhere
On the CBC technology section Bob McDonald writes…..
Cross-contamination between planets is a serious issue as humans begin leaving Earth. The human body is a microbe factory, with billions of organisms living on our skin, which we shed constantly, more microbes in our exhaled breath, coughs and sneezes, along with our water and food products. A colony on Mars would harbour more than humans. It would also be a microbiome of life that hitched a ride on bodies and in our spaceships. See:Bob