The sight of the entire Earth, visible to the naked eye, has had a profound effect on those who have seen it. Astronaut William McCool described it as “beyond imagination”, and many have written how space flight permanently altered how they saw their place in the universe.
For mission control, the wonder of space must seem like something of a distraction as they focus on the psychological health of their astronauts working in a high-pressure, high-risk environment, 420km (260 miles) above the Earth’s surface. These day-to-day stresses can be equally as life-changing and Nasa consider behavioural and psychiatric conditions to be one of the most significant risks to the integrity of the mission – not least as there is now significant evidence that space travel has mind-altering effects.
One of the most common experiences are frequent hallucinations that, despite sounding ominous, are probably the least concerning when it comes to in-orbit mental health. In the early Apollo missions, astronauts reported regular flashes or streaks of light that seemed to come out of nowhere. During a 2012 mission on the International Space Station, astronaut Don Pettit described these experiences as “flashes in my eyes, like luminous dancing fairies” that could be overlooked during work but would appear strongly “in the dark confines of my sleep station, with the droopy eyelids of pending sleep”.
These flashes attracted significant scientific attention, and a series of experiments determined that they are caused by cosmic rays: free moving subatomic particles from distant destructing stars. On Earth, most particles are absorbed by the atmosphere, but in space they cause nerve cells in the visual system to produce the “dancing fairy” effect.
Perhaps more seriously, hallucinations have been associated with the breakdown of crew coherence and space mission stress. In 1976, crew from the Russian Soyuz-21 mission were brought back to Earth early after they reported an acrid smell aboard the Salyut-5 space station. Concerns about a possible fluid leak meant the replacement crew boarded with breathing equipment, but no odour or technical problems were found. Subsequent reports of “interpersonal issues” and “psychological problems” in the crew led Nasa to conclude the odour was probably a hallucination.
Other Russian missions were thought to be have been halted by psychological problems, but the US space programme has not been without difficulties. During the Skylab 4 mission, long hours, exhaustion and disagreements with mission control resulted in the crew switching off their radio and spending a day ignoring Nasa while watching the Earth’s surface pass by.