Part 2 of 2 Parts (Please read Part 1 first)
Berea and her co-authors made their Martian colony population calculations using agent-based modeling. They used an opensource software application called NetLogo. She explained, “Agent-based modeling (ABM) is a class of computer simulations that encode 'agents'/individuals with the relevant attributes similar to the individuals in real life, and also the rules of interactions between these agents. In general, with ABMs we create simulations that are representative of a complex system and phenomenon from reality, where we can track the emergence of large patterns or phenomena out of simple rules of behaviors and interactions at the micro level. Additionally, we can explore a wide range of scenarios and we can isolate relevant initial conditions and parameters that are more likely to render the phenomena we observe in reality. This is especially useful for systems where direct causal phenomena is not easily deduced from data or experiments, and for systems where we have interactions between agents and various environments.”
Utilizing past research about how crews perform under stress drawn from submarine crews, Antarctic exploration teams, and soldiers in Iraq, the researchers created data models for Martian settlers. These included coping capacity, resilience, skill level, metabolism, stress level, and assorted environmental variables.” The models were then fed into the NetLogo software to create a simulation of the colonists.
After each Martian colonist was assigned one of four possible psychological traits including neurotic, reactive, social, or agreeable, the simulations were run. The model Martians could move, sleep, work with others, produce or consume resources, and interact. Without sufficient resources, the simulated Martians lose health points. When a colonist lost all health points, they died and were removed from the simulation.
Every seventy-eight weeks, a shipment from Earth might be received bringing four new colonists, each with their own personality traits. However, an accident might occur in transit which would cause stress on the colonists.
One of the results of running these model simulations is that mission planners may want to reduce the number of neurotics sent to Mars. The researchers found that “Martians with the 'neurotic' psychology die at a much higher rate than those of other psychologies, and once their population reaches a low enough level, the settlement population stabilizes.” Those with the agreeable personality type do the best over time.
Five runs of the models for a simulated twenty-eight years were seeded with initial population sizes ranging from ten to one hundred and seventy colonists in increments of ten. The paper says that “an initial population of 22 was the minimum required to maintain a viable colony size over the long run.” Berea said that “We wanted to show that if we neglect the social, behavioral and psychological aspects of space explorations, we can err grossly in our estimations, predictions and projections”.
Berea added that “Astronauts or regular humans that will explore space in one way or another are not amorphous entities, and our sociality and psychology will have a crucial role for these missions. Our social and behavioral aspects as humans can literally cut the line between the success and failure of a mission, especially a long term one, and can also be reflected in the economic costs of such missions.”