Hostile Space

A six-month stay in space induces physiological changes to the human body. A trip to Mars will be thrice that duration. Can astronauts survive the ordeal?

- Christopher Gaffney

IN THE FIRST 58 years as a spacefaring species, humans have mastered lower Earth orbit and missions to the moon. We are now in an age where not only government agencies such as NASA and Roscosmos have access to space, we now have commercial entities pushing the boundaries and ambitions for missions to Mars.

It took three days for the crew of the Apollo missions to reach the moon, a mere 0.38 million km away. On current technology, a mission to Mars will take around seven months to travel 55 million km, and this is if the planets align (literally) to make the journey shorter. A successful manned mission to Mars would arguably be the greatest achievement in human history. After decades of research on spaceflight, one crucial question remains: is it possible to send humans to Mars and return them in a healthy condition?

A mission to Mars presents significant physiological and psychological challenges. The body has evolved in a 1G environment on Earth, so our skeletal (movement) muscles, bones, balance (vestibular) system and our engine (the cardiovascular system) are all adapted to work effectively here on Earth.

Once in space, the body will begin to adapt to an environment without gravity, where physical and physiological capabilities are surplus to requirement. These changes take place on six-month missions to the International Space Station but it is a whole magnitude greater on a potential 18-month mission to Mars, where there is greater exposure to space radiation, limited space to exercise, and of course, three times the duration.

Skeletal muscles spend all waking hours resisting gravity and stopping us from crumbling to the floor. In space, muscle of the size and strength we are familiar with are excessive, so the body begins to get rid of them.