The psychological challenges of putting humans on Mars

Earlier this month, NASA named the four astronauts taking part in the Artemis II mission, which will be the first crewed flight to the Moon in more than half a century. The Artemis missions are part of a wider vision to take human exploration further into the solar system — space agencies hope that once they are able to sustain humans on a Moon base, they'll be technologically equipped to continue on to Mars.

But this poses a question: these missions might get our technology ready for the journey, but what about our astronauts? Just how ready will we be for the psychological challenges of putting humans on Mars? Engineering challenges come with a certain amount of predictability, but humans, with all their complexities and foibles, introduce a huge amount of uncertainty into any mission.

Human after all

Despite being portrayed as ultra-professional scientists with 'The Right Stuff', there are instances that show astronauts are as human as the rest of us. One of the better known examples is the near mutiny during Apollo 7, when the three-man crew became openly hostile to the ground control team. The crew was still reeling from the death of their colleague, Gus Grissom, in the Apollo 1 fire. This was compounded by the frustrations of early spaceflight technology, awkward sleep schedules, and the physical discomfort of spaceflight. This resulted in the crew's desire to impress that they were the ones in charge, which culminated in their refusal to wear their helmets upon re-entry, risking death from depressurisation. This mission ultimately ended their flight careers.

Examples such as these illustrate that crew members aren't always the logical, rational, superhuman entities we imagine, and in many ways the leadership traits that make them excellent explorers can be those that predispose them to risks — both physical and psychological.

In efforts to reduce the impact of these kinds of threats on mission success, space agencies have identified swathes of physical and psychological risks which will be encountered on a Mars mission and made them top priorities for research. NASA has formalised this list in the form of their Human Research Roadmap. Within this wide variety of anticipated psychological impacts, the most widely cited risk is isolation.

The perils of working remotely

Prolonged isolation can bring about a wide variety of negative emotional and cognitive effects. Tensions between crew, disturbed sleep cycles, and depressive symptoms have been observed across several studies. In the life-or-death situations presented by a Mars mission, any one of these could mean the difference between mission success or failure. This makes it vital to figure out mitigation strategies through research.

Isolation is studied in a number of ways here on Earth. In a space exploration context, agencies typically use analogue missions — field tests in locations that have physical similarities to the extreme space environments. These artificial replications allow space agencies to test both new technology and crew.

One of the most significant analogue studies was Mars 500 — a simulated Martian mission involving six male crew that lasted 520 days. During this time in isolation, the crew's behaviour and functioning was studied extensively.

On the whole, they lived and worked together remarkably well, with little significant conflict. However, it was clear that the constraints of the environment affected both their behaviour and biological functioning. The lack of natural light threw off four of the crew's circadian rhythms, with one crew member shifting to a twenty-five-hour cycle, and others showing extensive daytime napping and chronic sleep deprivation. The majority of operational errors were attributed to lack of sleep, and it's easy to imagine the conflicts that could result from sleep disturbances in a less-harmonious crew.

Of course, analogues like Mars 500 can't adequately reproduce the challenging, dangerous environment of a real interplanetary mission. The additional stressors encountered on such a mission may well exacerbate problems caused by sleep or other effects of isolation. Many psychological researchers therefore prefer to study analogues that offer real consequences to crew members, should they fail their mission. For this, they conduct research in more extreme conditions.

Active antidotes

LUNARK was the first lunar analogue mission conducted in the Arctic. Performed in the remote environment of Northern Greenland, this study tested approaches for maintaining astronaut wellbeing, and explored factors which may reduce negative outcomes from isolation in a realistic setting.

During the 61-day mission, two participants lived and worked in a small, ergonomically designed habitat called the LUNARK. Given the perilous conditions outside, the two were constantly in close proximity, yet far from loved ones, with little to distract them from the situation. Communications with the outside world were very limited, comprising only daily 160-character messages sent via satellite phone to their "ground crew" in Denmark. Much like astronauts, their days were spent completing research in their tiny quarters, physically and socially isolated from the rest of the world.

To record their experiences during this simulated Moon mission, both participants kept daily diaries, full of self-report measures evaluating their daily activities and emotions. These measures probed feelings of loneliness, resignation, desire for social contact, and time perception.

Analysis of these diaries revealed several things. Firstly, desire for social contact increased over the duration of the mission. This is a desirable outcome, as previous studies have noted the tendency for crew to become depressed and socially withdrawn as lengthy missions progress. Talking about personal topics and exercising both strengthened this desire for social contact.

Feelings of resignation stayed relatively steady across the mission, and chatting about personal matters and taking leisure time protected against these negative feelings. And, as the old phrase "time flies when you're having fun" suggests, leisure time was also associated with increases in the perceived speed of time.

The environments astronauts face off-planet will be harsh and unchanging. But this study suggests that even in such unforgiving situations, careful activity management may be an effective method for dampening particular mission-associated stressors.

Other such strategies are already in place in missions closer to home than the Moon. Astronauts on the International Space Station have regularly scheduled calls home, leisure time with internal cameras turned off, and even special treats to raise morale, such as calls with their favourite celebrities. As with Earth analogues, though, the knowledge they'll be home soon remains, making it tricky to draw comparisons between the psychological challenges of missions to low Earth orbit and journeys to Mars.

Selecting for the unexpected

Of course, space agencies have their eye on minimising the effects of isolation long before an astronaut ever goes on mission. Selection processes for non-commercial crew, which are rigorous and highly secretive, are said to select for candidates who will be resilient to the challenges of spaceflight. This includes the isolation of being far from loved ones and external assistance.

The selection process has served space agencies pretty well for missions to date. Even during the Apollo era, selected astronauts were equipped for incredibly stressful situations.

For all our efforts, though, it's likely that some of the psychological challenges of putting humans on Mars are not things we can foresee. Before the Apollo missions, astronauts and the public alike were enticed by the idea of seeing the Moon up close and putting humans on its surface. When the programme began, however, some of the most emotionally striking images were of our home planet seen from afar. Gazing at Earth from orbit, astronauts found themselves facing profound shifts in their outlook on the world, feeling a sense of interconnectedness and renewed purpose. For many, these changes would last a lifetime after their return.

This unexpected psychological phenomenon became known as the Overview Effect.

Author Frank White first formally wrote about the Overview Effect, and interviewed multiple astronauts about their experiences. It has also been relatively well-documented in the academic literature. Astronauts often report intense feelings of interconnectedness when viewing our home planet from orbit. NASA Astronaut Edgar Mitchell explained his experience of the phenomenon as being like an "explosion of awareness", and an "overwhelming sense of oneness and connectedness... accompanied by an ecstasy… an epiphany" — a view seemingly similar to that of commercial astronaut William Shatner, who recently provided a stunned, emotional reaction upon his return to Earth.

The Overview Effect was unexpected — which raises the question of how astronauts might respond after travelling much further into space. From the vantage point of an astronaut on Mars, Earth will appear to be little more than a star in the sky. While space agencies continue to prepare for interplanetary missions to the best of their ability, and aim to be ready for whatever comes, it's impossible to fully anticipate the effects that such extreme remoteness may have on the psychological state of our first Mars crew.

Correction, 20 April 2023: A previous version of this article referred to Frank White as an astronaut rather than an author. This has been corrected.