In 82 years, humans went from building the first skyscraper to building a skyscraper that burned 15 tons of fuel each second and could send people to the moon. Sending humans to Mars may have seemed like an inevitable next step after the moon landings of the Apollo program. But as the Cold War ended, so did the space race that led to the moon landings.
Decades have gone by and Mars is still on the horizon, untouched by man. But recently, new technology has brought journeying to Mars back into public interest. Why go to Mars? We know it will cost billions of dollars and risk many human lives. However, there are several arguments for exploring Mars in-person and eventually colonizing the planet. Human presence could lead to the discovery of past or present life on Mars. We could find that another form of life altogether or even that Martian life and Earth life share the same ancestry. And in the long run, colonizing Mars could greatly increase humanity’s chances of survival. A self-sufficient colony could preserve the species if an asteroid, nuclear war, or epidemic wiped out humans on Earth. Mars is a common goal to strive for, an enticing frontier to conquer.
Though the dream is captivating, we must question its feasibility: Are any of the musings above possible? The first hurdle is delivering humans to Mars safely. Earth and Mars must be at opposition, where the two planets are at their closest in orbit. This happens about once every two years. The distance to the red planet can sometimes drop under 40 million miles but is often much greater. Unless there is a major advancement in propulsion technology, astronauts should prepare for a journey lasting the better part of a year. Thus, scientists are using the International Space Station (ISS) to test the effects of prolonged lack of gravity on the body. Astronaut Scott Kelly recently completed an entire year on the ISS to test these effects while his identical twin stayed on Earth. The analysis is still ongoing, but researchers have found that Scott’s cognitive performance decreased slightly during flight and dominant bacteria levels in his gut changed. In deep space, cosmic rays also become a threat to human health. These high energy atomic nuclei can damage DNA, but they could be shielded by a layer of water surrounding the crew cabin.
NASA states that they plan to put a human on Mars in the 2030s using the new Space Launch System (SLS, a heavy expendable launch vehicle), and the Orion spacecraft. NASA first plans to use the SLS to send an unmanned Orion capsule around the moon in late 2018 and perform the same crewed mission as soon as three years later. In 2020, they plan to redirect a boulder from an asteroid into Earth’s orbit and later send a crew to explore and sample it. These plans aim to prove that the SLS and Orion can operate dependably and without relying on Earth for resupply, which will be critical for Mars Missions. NASA’s slow and steady approach emphasizes crew safety and gradual steps towards footprints on Mars.
NASA is not the only organization working on interplanetary transportation. SpaceX has laid out ambitious goals to develop an Interplanetary Transport System that could also deliver humans to Mars. The aim of this system is to dramatically reduce the cost of getting to Mars through reusability. The first stage would shuttle crew and cargo to Earth orbit and land back on Earth to refuel. If this approach reduces costs enough, explorers could pay to go to Mars and cover the costs of the journey.
The next challenge is slowing down and landing safely on the Martian planet. Because the thin atmosphere is not enough to slow a lander down even with parachutes, retropropulsion is necessary. In a previous mission to the Red Planet, NASA used a rocket crane to lower the Curiosity Rover to the surface of Mars. But any manned vehicle that could return into Mars’s orbit would have a mass 20-30 times greater than that of the rover and would be much harder to anchor. In addition, reliability standards would need be even higher with humans on board.
Using Martian resources will be crucial to the success of a mission. Water-ice has been discovered near the surface of the planet, and could be separated into hydrogen and oxygen to use as fuel for a return trip. Another approach that several experts have proposed uses the abundant carbon dioxide (CO2) in the Martian atmosphere. Hydrogen could be shipped to Mars at a fraction the mass of a fuel like methane, and then combined with the available CO2 in a Sabatier reactor to produce methane and water. This reaction actually releases energy and is currently used to produce water in the International Space Station. CO2 could also be decomposed at high temperatures to produce O2, which is furthermore necessary for fuel. Generating these vital resources requires large amounts of energy. A solution, solar panels would work although not as much sunlight hits Mars as Earth. NASA is also researching alternative methods for energy production such as nuclear fission.
Once humans reach Mars, the subsequent step is keeping them alive. Mars’s atmospheric pressure measures in at a mere fraction of the Earth’s; direct exposure to such low pressures would result in body liquids boiling. A suitable habitat on Mars would have to be adequately pressurized and oxygenated. In addition, because the Red Planet has no magnetosphere like the Earth does, astronauts must be protected from cosmic radiation on the Martian surface. For this reason, scientists at NASA are developing hydrogenated boron nitride nanotubes that could be woven into spacesuits to shield astronauts from harmful particles. The walls of the habitat would also need such protection.
Sending humans to Mars will be the most challenging collective endeavor humanity has ever undertaken. It will require contributions from the fields of physiology, rocket science, chemical and electrical engineering, and dozens more, and will cost a tremendous amount of money and possibly several lives. But unlike the moon landings, the journey to Mars would mean much more than a historic achievement and being able to say “We’ve been there.” Humans will not only explore Mars, but might one day call it home.