In order to make an organised effort to overcome the obstacles that lie before a human journey to Mars, NASA has listed five hazards that astronauts can encounter on the red planet. These hazards are being studied using ground-based analogues, laboratories, and the International Space Station (ISS), which serves as a testbed to evaluate human performance and counter-measures required for the exploration of space, the US space agency said in a statement.

NASA's Human Research Program divides the hazards into five classifications- radiation, isolation and confinement, distance from Earth, gravity (or lack thereof), and hostile or closed environments. "Various research platforms give NASA valuable insight into how the human body and mind might respond during extended forays into space," NASA researchers said, adding, "The resulting data, technology and methods developed to serve as valuable knowledge to extrapolate to multi-year interplanetary missions."

The first hazard of a human mission to Mars, NASA says, is also the most difficult to visualise because space radiation is invisible to the human eye. Radiation is not only stealthy but considered one of the most menacing of the five hazards.

Behavioural issues among groups of people crammed in a small space over a long period of time, no matter how well trained they are, are inevitable, according to NASA. Crews will be carefully chosen, trained and supported to ensure they can work effectively as a team for months or years in space, it said.

The third and perhaps most apparent hazard is the distance. Mars is, on average, 140 million miles from Earth. Rather than a three-day lunar trip, astronauts would be leaving our planet for roughly three years, the statement said.

NASA noted that the variance of gravity that astronauts will encounter is the fourth hazard of a human mission. On Mars, astronauts would need to live and work in three-eighths of Earth's gravitational pull for up to two years, it noted.

NASA also understands that the ecosystem inside a vehicle plays a big role in everyday astronaut life. Important habitability factors include temperature, pressure, lighting, noise, and quantity of space. It's essential that astronauts are getting the requisite food, sleep and exercise needed to stay healthy and happy, it said.