2.2.2 MOC in the natural environment

Organic molecules are very good at binding to sediments. This is really useful for biosignatures, because minerals have been shown to help preserve organic molecules over time. However, it also means they pose a contamination risk to the natural environment.

For example, you may have heard of a group of chemicals called polychlorinated biphenyls (PCBs). On Earth, these are a group of persistent organochlorine pollutants that don’t break down easily, are hydrophobic (water hating) and can bind strongly to sediments. This means they can remain as a long-term contaminant in the natural environment and have even been detected in Antarctica and in dust collected from the International Space Station.

On Earth, their use and disposal are regulated but they have been used in coolants and hydraulic fluids for their thermal and chemical stability, or as plasticisers in paints and as flame retardants in adhesives. This included in the construction of spacecraft or satellite systems. However, now that it is known that these can emit unwanted and dangerous chemicals, they are no longer used. 

This has not, however, eliminated all MOC from spacecraft, and as you will learn later, there are further planetary protection mitigations required in some circumstances. Before you learn what those are, the next section shows the potential negative impact of MOC on the lunar environment.