What’s the Bare Minimum Number of People for a Mars Habitat?

A recent preprint paper examines the minimum number of people required to maintain a feasible settlement on Mars while accounting for psychological and behavioral factors, specifically in emergency situations. This study was conducted by a team of data scientists from George Mason University and holds the potential to help researchers better understand the appropriate conditions for a successful long-term Mars settlement, specifically pertaining to how those settlers will get along during all situations. But why is it important to better understand the psychological factors pertaining for a potential future Mars colony?

“We cannot think of any type of habitat or future human settlement without including human behavior, psychological or social,” Dr. Anamaria Berea, who is an associate professor in the Computational & Data Sciences Department at George Mason University and a co-author on the study, tells Universe Today. “We humans are not robots, and even the best trained astronauts have different personalities and modes of interaction with each other and with their extreme environment. But on the long run and for long duration missions, team behavior is a crucial factor for the success or failure of a mission.”

For the study, the researchers used an Agent-Based Modeling (ABM) method to gauge interactions of future Mars colonists, known as agents in the study, and who exhibit a variety of personality types and skill levels that they will use for operating a Mars colony mining for minerals. The four personality types include Agreeables, Socials, Reactives, and Neurotics, where aggressiveness and competitiveness are ranked from lowest to highest, respectively. In addition, each agent’s skill level is associated with management or engineering that they will use to contribute to the colony’s mining needs.

“A psychologically diverse population is more desirable,” Dr. Berea tells Universe Today. “In our paper, the ‘neurotics’ are actually needed for high-risk tasks; therefore, they are more likely to solve the problems in case of accidents, but also risk their lives. In the simulation, we start with equal percentages of psychological diversity, and then we see who survives in the system and who does not.”

The ABM focused on how each personality type coped with both their increasing time on Mars and emergency situations, such as resupply shuttle accidents and habitat disasters, noting the colony would be largely self-sustaining with two-year resupply missions from Earth. The researchers noted their goal with this study was to address fundamental questions pertaining to the conditions necessary to maintain a feasible Mars colony, the personality type combinations that would perform the best in a Mars colony, and the required number of resources necessary to maintain the Mars colony given the two-year gap between resupply missions from Earth. Additionally, these came with the assumption of periodic accidents either with the resupply missions or within the colony itself.

Additional ABM parameters also included how the agents coped with the local mining economy and harsh Martian environment, specifically regarding the solar radiation bombarding the Martian surface; how the Martian economy could operate outside of the colony; and using energy sources in space, specifically the potential for solar power and nuclear fission. The researchers referenced the International Space Station and outposts in Antarctica as a baseline for their study.

Using the ABM, the researchers ran five simulations with each comprising 28 Earth years and population sizes ranging from 10 to 50 agents, with increases of 10 agents in each simulation. In the end, they determined that a minimum colony population of 22 agents was ideal to maintain a feasible Mars mining colony over the long-term. Additionally, the researchers found that the Agreeable personality type not only performed the best but was the only personality type to survive the full term for all ABM simulations. However, the researchers were quick to note future work is needed to better understand the assumptions described in this paper.

As noted, the simulated Mars colony for this study was largely self-sustaining, though not fully self-sustaining, as the colony relies on resupplies from Earth every two years to ensure both its short-term and long-term survival. While this study found a minimum colony population of 22 agents was ideal given the parameters, could there be a minimum population size needed for the colony to be fully self-sustaining, meaning no engagements with Earth or other off-Earth settlements (i.e., Earth’s Moon)?

“I don’t think something like this can exist,” Dr. Berea tells Universe Today. “We know historically that isolated cities or villages or even countries cannot thrive. In the extreme environments habitats designed on Earth from scratch, such as under the sea or in Antarctica, there are periodic replenishments of people or supplies. Nobody lives there isolated forever. That’s why in our model we assume that there are some interactions with Earth, even if sparse sometimes. The scenario where we send a number of people on Mars on a one-way trip and never hear from them or interact with them again, seems very implausible to me. If we successfully send people there once, I am pretty sure we will be able to send supply shuttles many times. It’s also more cost-efficient.”

A prime example of an alleged one-way trip to Mars was with the private Dutch company, Mars One, which proposed sending people to Mars for good in hopes of establishing a permanent human settlement on the Red Planet. This was met with both enthusiasm and harsh criticism, specifically pertaining to Mars One not being an aerospace company or building their own hardware. Though applications for eager Mars-bound travelers went through several rounds, Mars One eventually declared bankruptcy in 2019 having never launched a single mission.

This recent study builds on several previous studies that attempted to estimate the minimum number of people required to maintain a Mars colony, with a 2001 paper, a 2003 paper, and a 2020 paper each estimating a minimum of 500, 100, and 110 people, respectively. But if this most recent study proves accurately that a future Mars colony will only need a minimum of 22 people to maintain it, how soon after we start sending humans to Mars will a potential colony reach this minimum number of 22?

“I believe the first time humans will set foot on Mars will not be for any kind of permanent settlement or colonization, but for exploration and for laying the ground for future missions,” Dr. Berea tells Universe Today. “We don’t yet know when that will happen, it is still years in the future, and after that there will be more years before actually considering sending humans for permanent or semi-permanent settlements. So, I don’t think this will happen in the near future yet.”

When will we go to Mars and what will be the minimum population required to maintain a feasible colony there? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!