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A spacecraft on the surface of another planet sends a signal home that it has found the building blocks of life. How can you be sure that it wasn’t something from Earth that hitched a ride? Bacteria can survive a lot of stress and extreme environments, making it easy to survive an interplanetary trip. Logistically and ethically, this presents a problem.
This is exactly what NASA has addressed with the Office of Planetary Protection. They have many goals to conform to international standards including preserving other worlds’ natural states and protecting the “Earth’s biosphere in case life does exist elsewhere”.
The person in charge? Dr. Catherine A. Conley, Planetary Protection Officer. She guides the missions through the proper steps for each destination based on the category that location was placed in. Category I is for a location with no relevance to chemical evolution. As soon as there is a remote chance of contaminating a place for future exploration it becomes Category II. The moon falls in this category.
When it becomes a significant risk, it is Category III and then IV (which is broken down into further categories for Mars missions). Finally, there is Category V. This is only used when a spacecraft is returning to Earth. Any returning craft, that visited an alien body, has to stay in strict containment until it can be confirmed it is clear of extraterrestrial life.
It’s unknown whether such life exists on other planets or what that life might even look like, so all these regulations are designed with protecting life in mind.
Music for podcast: Jeux d’eau by Maurice Ravel as performed by Allison Lovejoy