In 1961, John F. Kennedy famously said he wanted to put a man on the moon. But if JFK were around today, he might say, “let’s put a woman on Mars”—not in a nod to diversity or inclusion, but because a Mars mission will be the longest and most mentally taxing of any mission astronauts have ever faced. And research is telling us that women might be better suited, both biologically and psychologically, for long-distance space travel.
The first advantage women have is that they typically weigh less than men and require 20–25 percent fewer calories to maintain their weight. The more a spaceship carries, the more fuel it takes to propel a rocket past the stratosphere and on to the Red Planet (and the more fuel a rocket carries, the more fuel it needs to lift that fuel along with everything else). Today, it costs about $10,000 per pound to propel something into space, so even the smallest discrepancy in weight makes a significant difference.
Women also have a psychological edge. Astronauts going to Mars will have to live together in a confined space for up to three years, forced to deal with the challenges of interacting and sometimes clashing personalities. There’s really nowhere to go if things get tense.
Women might also have the communication style needed to ease potential clashes that arise from close quarters and time delays.
Research has also shown that while men do better in shorter-term goal-directed situations, women have an edge when it comes to handling longer-term missions. NASA has studied the journal entries of astronauts who spent prolonged periods on the International Space Station and found that women report fewer episodes of negative moods than men.
Lastly, one of the biggest hurdles Mars-bound astronauts will face is that of exposure to galactic cosmic rays (GCR), a type of radiation specific to deep space. GCR are fast-moving, electrically charged particles that come from interstellar space. On Earth, we’re shielded from them by our planet’s magnetic field, but once a spaceship leaves that protective bubble, the particles can fly right through the walls of the spacecraft and through astronauts’ bodies. Once the rays interact with the living tissues, they deposit energy that alters the structural integrity of cells and DNA. Although there have been other missions that have left low Earth orbit, they have lasted only a matter of days, making the risk of radiation-induced health problems much lower. In the case of a Mars mission, will face up to about two years of exposure to this type of radiation.
Bombardment with cosmic rays can cause cancer, vision impairment, and heart disease, but it can also potentially affect the astronauts’ brains. I work on a research team led by Susanna Rosi at the University of California, San Francisco, that looks at how simulated GCR can trigger changes in the brain cells of mice, which can lead to behavioral and cognitive changes. We have found that exposure leads to increased anxiety, impaired memory and diminished social interaction in male mice—but not in females.
The reason female mice are protected from these changes seems to lie in the microglia, the brain’s resident immune cells. Microglia have a resting state and an active state, and they become activated when there’s some sort of insult to the brain. Microglia activation can cause inflammation in the surrounding brain tissue. For some reason, exposure to space radiation activates these cells in male mice only and can cause synapse loss in the hippocampus, the brain structure that mediates memory formation.
Givenalactic cosmic rays could impair some of the necessary skills needed for a successful mission, including memory, sociability and a stable mood. These skills will already be taxed on the long journey to Mars, making it even more imperative to protect astronauts from long-term exposure. NASA has, of course, investigated various shielding methods to protect astronauts from these harmful rays, both on the outside of the space shuttle and on the astronaut’s spacesuits.
However, there are many challenges to physical shielding, such as the additional weight it adds to the spaceship that make it prohibitively expensive, and that GCR is more powerful and harder to shield against than the radiation from solar particle events (SPEs) that are found in near-Earth orbit. Still, NASA and researchers like Rosi are dedicated to finding safe technologies to support successful space exploration.
Women may be more physically economical, psychologically equipped and seemingly immune to radiation-induced cognitive deficits, but does that mean NASA should send an all-female crew to Mars? Not necessarily. Understanding what makes us so biologically distinct could hold the keys to our future and success in the final frontier.
We can use the information about why women are protected in order to find a way to protect men too. Rosi and her team have shown that it is possible to protect mice from radiation-induced cognitive deficits by depleting and repopulating microglia. After the mice were irradiated, they received a drug that blocked the receptor necessary for microglia to survive.
Once all of the microglia were eliminated, the mice were taken off the drug. Then, the microglia naturally repopulated in the brain, but these microglia were as if they had never been radiated. In effect, a “refresh” button was pressed on these cells. When the mice underwent cognitive and behavioral testing, the animals who received the treatment were protected against radiation-induced cognitive deficits. Of course, even if it works in humans as it does in rodents, which hasn’t yet been demonstrated, this pharmaceutical countermeasure might protect astronauts from other aspects of radiation. But it would be one small step in the direction that could lead to the giant steps necessary to land a crew on Mars.