As few as 22 people could sustain a colony of pioneers long enough to establish a human presence on Mars.

That's the conclusion of a new study by a team of researchers in the US that used modeling and simulation to work out the minimum initial population size for a successful Mars colony that goes on to thrive.

Any fewer, and your colony could be a dud that goes the way of Lord of the Flies, or worse.

That's a lot lower than a previous estimate of 110 people. The more the merrier, perhaps, though the travel bill for a trip to the Red Planet would skyrocket with every extra mouth to feed.

But it's not just the number of people. The researchers found the simulated Mars colony has to have the right mix of personality types for working together for a long time in a very isolated environment or the whole thing could just go belly-up.

These findings, yet to be peer-reviewed, have been detailed in a paper uploaded to preprint server arXiv.

A rendering of a potential Mars habitat. (Hassell & EOC)

A crewed mission to Mars in humanity's near future is starting to seem more like an inevitability than a possibility. Until we've been there, we won't know how viable a long-term colony or base might be, but we do know it will be difficult, with many problems to solve.

"Beyond mining a few basic minerals and water, the colonizers will be dependent on Earth resupply and replenishment of necessities via technological means, i.e., splitting Martian water into oxygen for breathing and hydrogen for fuel," the researchers write.

"Beyond the technical and engineering challenges, future colonists will also face psychological and human behavior challenges. Our goal is to better understand the behavioral and psychological interactions of future Martian colonists through an Agent-Based Modeling (ABM simulation) approach."

Agent-based modeling is a technique usually used in health or economic research. Basically, they're computer simulations designed to study the interactions of autonomous decision-making 'agents' in a system. Though usually focused on people, the system can also include objects, location, and the passage of time.

The team included in their modeling four personality types:

  • Agreeables, with low competitiveness, low aggression, and low fixation on routine
  • Socials, who are moderately competitive, competitive in social interactions, and require social interaction, but also have low routine fixation
  • Reactives, who are moderately competitive, competitive in social interaction and fixated on routine
  • Neurotics, who are highly competitive, aggressive socially, highly fixated on routine, and have trouble with boredom.
An artist's depiction of a possible Mars habitat. (SEArch+/Apis Cor)

Each agent was also assigned skills from two categories; management and engineering. Other factors, such as resource availability, interpersonal relationships, and task pairings, were also taken into consideration.

The team studied human forays into high-stress isolated environments, such as Antarctica, submarines, and the International Space Station, to gain a better understanding of the challenges and stressors.

The team performed 5 runs of their model for a span of 28 years, varying the population size from 10 to 170 in increments of 10 individuals, later testing even smaller initial populations.

Since there are four critical tasks that need to be constantly carried out – such as air, water, and food production, as well as the removal of waste and accident recovery – a population size of 10 was set as the absolute bare minimum for a stable colony. Equal numbers of each personality type were included in every starter set.

After 28 years, the minimum starting population that was able to sustain a population higher than 10 individuals was 22 people. But personality type played a significant role.

"In all runs, the Agreeable personality type was the only one to survive the full duration of model runs," the researchers write.

"This is likely because it has the highest coping capability, and after long periods of time every agent has been exposed to a series of stressor interactions, as well as space and habitat accidents."

Perhaps unsurprisingly, though, neurotic personality types represent a liability within the simulation. The team found that neurotics drive Martian population decline. They die at a much higher rate than other personality types; and it's only once neurotic personalities have reached a low enough level that the rest of the population can stabilize.

Luckily, this information isn't new to NASA, which already selects astronauts only after a long and careful vetting process that includes personality assessments.

However, the research shows just how important it can be to factor the human into human mission planning.

The research appears on preprint server arXiv.