Challenges facing the human exploration of Mars

Breathing easy and getting home again

Rather than bringing large quantities of oxygen to Mars, future astronauts could live off the land, using materials they find on the planet’s surface to survive. This concept, called in-situ resource utilization (ISRU) has now been proven by an instrument on the Perseverance rover. MOXIE (Mars Oxygen In-Situ Resource Utilization Experiment) extracted oxygen from Mars’ thin atmosphere and was able to produce 12 grams of oxygen an hour – twice as much as the original goal for the instrument. 

Not only could a larger MOXIE-like system supply breathable air, but it could also help create rocket propellant, which will be required in massive quantities to launch rockets with astronauts for their return trip home.

Michael Hecht, the instrument’s principal investigator from the Massachusetts Institute of Technology (MIT) said he and his team would be ready to scale up the system if funding was available.   

“Particular technical tasks might be demonstrating longevity, both for the electrolysis stacks and the compressor, and developing a prototype liquefaction and storage system,” Hecht said. “Beyond that, the mining of water ice to enable more complex chemistry, including fuel production, would be a priority.”

While oxygen is the heaviest component of propellant, it is fortunately the easiest to make, Hecht said. And even though water ice appears to be plentiful on Mars, the logistics of mining it and transporting it to where it is needed would need to be determined. 

The biggest challenge: entry, descent and landing

Before astronauts can leave the surface of Mars, they must first get there. The biggest challenge in exploring Mars might be slowing down a large, human-sized spacecraft from speeds of tens of thousands of kilometers per hour to enable a touchdown gentle enough for astronauts and payloads to survive. 

So far, landers and rovers have used parachutes, airbags, or sky-cranes to safely land on the Red Planet, but these technologies have likely reached their limits. The Perseverance rover – currently the largest rover or lander sent to Mars — has a mass of about 1 metric ton. But a human mission to Mars will likely require a vehicle between 50 – 100 metric tons, depending on the configuration. These larger vehicles will be too heavy to be slowed significantly by aerodynamic drag in Mars’ thin atmosphere, which has less than 1% the density of Earth’s.