1.3.2 Biohazards
A satellite returns to Earth carrying with it a mysterious extraterrestrial lifeform that is deadly to humans. Scientists rush to investigate what this organism is, how it is transmitted, and how to contain it to prevent it from killing all life on Earth.
If you are an avid science fiction reader, you may recognise this as the plot of the 1969 book ‘The Andromeda’ strain by Michael Crichton, but you may be familiar with similar tropes from many movies and television series. Whilst fictional and (we hope) greatly exaggerated, it is scientifically plausible that life (or other contamination) could be carried to Earth via spacecraft or within one of samples returned from another planetary body. As such, science fiction scenarios such as the one above present a powerful allegory for the risk of biohazards from space.
Hazards and risks
A hazard is a potential source of harm and can be an object or a situation that poses a level of threat to life, health, property or environment.
A biohazard is a biological substance that could pose a threat to human health or the environment.
Hazards are components of risk, along with the probability of an event coming to pass. Risk also depends on the nature of the consequences arising from the event.
The simplest form of risk assessment is to rate the risk as high, medium or low. The two elements to risk that have to be considered are the likelihood of harm, and the severity of that harm if it were to happen. The process of risk assessment seeks to answer the questions: ‘what can go wrong?’, ‘how bad are the consequences?’, ‘how often might it happen?’, ‘who might be harmed?’ and ‘is there a need for action?’
Recall the habitable environments that we discussed earlier. The Earth has many environments that harbour life, but some of these are fragile and any sort of disruption – such as changing the physical or chemical conditions of the environment or introducing life that might disrupt the local ecosystem – could be catastrophic. In the context of planetary protection, we describe this contamination to the Earth’s environment as backward contamination, in contrast to forward contamination we discussed earlier.
In the face of such consequential scenarios, control measures are needed to mitigate (reduce) the risk. This is where planetary protection comes in, with international guidelines, containment measures and cleaning protocols. You will meet all of these shortly, but for now, let’s look in more detail at what it is that we are protecting space from.