Q: Do we have the knowledge today to send humans to Mars, or is technology not yet ready to guarantee an astronaut’s safety on a journey to the Red Planet? (Claudio Rosmino, Lyon, France)
Getting to Mars is a very big technical challenge. We don’t yet know all the technologies or techniques we will need to send humans safely to Mars and back. Here are some of the major challenges we face:
It takes 6 to 9 months to reach Mars, and an equally lengthy voyage to return to Earth. We don’t have reliable life support machines needed to keep the crew alive over such a long voyage (and on Mars itself); they will need repairs and spare parts. The reliability needed from our life support system has been described as equal to that of submerging a submarine and never surfacing for three years, while keeping its crew safe and healthy. We don’t know how to do that on Earth, let alone on the way to Mars and back.
Secondly, we don’t know how to land heavy spacecraft on Mars. Mars’ atmosphere is too thin for parachutes to land spacecraft safely, yet thick enough to require a heat shield to get down through its upper layers. Mars gravity is strong enough (one third that of Earth) that our landers will require rockets for final descent. Our best effort so far has put a ton (the Curiosity rover) on Mars. We will need to build landers that can deliver 10 or 20 tons, perhaps up to 50 tons, to put astronauts and all their cargo on the surface.
Lastly, there is the unsolved problem of radiation exposure. Astronauts enroute to Mars and back will be bathed in cosmic ray radiation, and subjected to occasional solar storms. The shielding needed to protect them (hydrogen, water, or sandbags filled with Moon or asteroid “dirt”) is too heavy for our rockets to push to Mars. On Mars itself, crews will have to live underground, protected by several meters of Mars dirt. NASA has about 20 years of homework ahead of it to solve this radiation challenge.
I am optimistic we will conquer these challenges, but it may be 2040 before we can reduce the risk to astronauts enough to send the first expedition there. I hope you’ll help us solve some of these problems.