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How could contamination cause a false detection of extraterrestrial life?

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Planet TOI 700e — extraterrestrial life An illustration of the Earth-size planet TOI 700e orbiting within the habitable zone of its star. The habitable zone is the area around a star where liquid water, and thus possibly life, can survive on a planet's surface. Its Earth-size sibling, TOI 700d, can be seen in the distance.

In the field of astrobiology, contamination poses a significant risk to the integrity of life-detection experiments. A primary concern is that a spacecraft may inadvertently carry living organisms from Earth to a target planet, leading researchers to mistakenly report them as indigenous extraterrestrial life.1

To mitigate this, robotic missions are subject to rigorous sterilization protocols, particularly for components that contact a planetary surface, to ensure that terrestrial materials do not interfere with the search for native life.2

Contamination can also complicate the analysis of extraterrestrial samples, such as meteorites. Because these objects are porous and interact with Earth's atmosphere and storage environments, they are susceptible to the introduction of terrestrial microorganisms. For example, researchers have previously identified ragweed pollen and other contaminants within meteorites, which can lead to misleading claims regarding the presence of biological matter. Consequently, because no single, unambiguous "life detector" exists, scientists must rely on a combination of highly specific and general instruments to verify findings and distinguish between genuine extraterrestrial life and terrestrial contamination.1