If you believe the news, a human mission to Mars is no longer a sci-fi fantasy. But what problems would we need to overcome? And should we even try?

The Horizon Probe is about to make its closest approach to the dwarf planet Pluto, having completed an eye-watering nine-year, three-billion-mile voyage. Pluto is so distant that it lies in the Kuiper Belt, a region of the Solar System beyond the planets. This raises the possibility that space travel might one day be boundless.

For now, though, all eyes are on Mars, a mere 180-day journey away and a possible target for a future human colony. And this isn't merely science fiction—the space race has already began.

 

Mars One

Mars one colony
The Mars One settlement 

One example is Dutch company Mars One, which plans to launch a one-way-trip with four astronauts to Mars, landing in 2027. Additional crews will join them every two years to form a colony. Sceptics largely dismiss Mars One as a stunt, but a more viable proposition is Nasa’s Orion, the first mission since Apollo designed to take humans into deep space. A return trip to Mars is planned for the 2030s.

In preparation for this, Nasa and the European Space Agency (ESA) are studying Mars with a host of spacecraft, in an attempt to solve the mystery of how Mars lost most of its atmosphere. In 2021, Nasa’s rover will test an experimental weather station on Mars and also a device to convert carbon dioxide into oxygen.

Much has been discovered already. Two of the most exciting finds this year concern water, one of the vital ingredients for life as we know it. Using powerful infrared telescopes, Nasa scientists have confirmed that Mars once had more water than the Arctic Ocean, and some of this remains locked up in Martian polar caps. The Hubble Space Telescope, meanwhile, discovered yet more water beneath the surface of Jupiter’s largest moon Ganymede—another future space destination.

 

How do we get to Mars?

The furthest we have sent astronauts is to the moon, about 240,000 miles away. This is small fry compared to the 35-million-mile journey to Mars. Reaching the red planet will require some serious hardware. Nasa will use its new heavy-lift rocket the Space Launch System (SLS) to propel Orion—the new generation of spacecraft—into space. The SLS is more powerful than any previous rocket, firing over 8.4 million pounds of thrust, equal to 135 Boeing 747s. The computers running the software on Orion have the ability to handle 480 million instructions per second. 

There's been speculation that astronauts will be put into “hyper-sleep” (a therapeutic coma) during the journey to Mars and kept alive intravenously, to conserve resources. Although a favourite trope of sci-fi films, experts think this unlikely.

 

How will we live? 

Mars one living quarters
The Mars One living quarters 

Humans will need self-sustaining water, food and oxygen to survive on Mars. Extracting water locked up in ice will be crucial, but with the recent discovery of flowing water on Mars may not be too difficult.

Nasa is developing an excavator device called RASSOR (Regolith Advanced Surface Systems Operations Robot), designed to mine water, ice and fuel from planetary soil. Mars One also plans to send a water extractor to heat the soil until the water evaporates. The water will then be condensed and stored, the dry soil expelled and the process repeated. Mars One claims its astronauts will have 50 litres of recyclable water every day. 

Food will need to be grown and harvested, but farming in space isn’t easy. You can’t plonk crops into earth and sprinkle on water, because in microgravity free soil and water will fly around and “foul the interior of the spacecraft”, warns Dr Anna-Lisa Paul, expert in molecular and cellular biology at the University of Florida.

“Plants can be grown in space, but all require the management of gasses, water and a growing substrate,” says Dr Paul, who’s been studying the use of Arabidopsis (thale or mouse-ear cress) on the International Space Station. The crop is perfect for Mars, able to grow on a 10cm petri dish and closely related to vegetables such as broccoli and radish. It matures quickly and scientists already know its complete genetic code.

Special growing systems will be required, such as VEGGIE (the Vegetable Production System project), a microwave-sized chamber in which plants receive carbon dioxide and controlled-release fertiliser, and fans stir the air (heavy gasses sink and light ones rise on Earth, but in space this doesn’t happen).

Food might also be “printed”. Nasa is working with Systems & Material Research Corporation (SMRC) to develop a 3D printer to mould protein, starch and fat into shapes and microjet in flavours and nutrients. David J Irvin, director of SMRC, predicts there will be 25 to 50 basic food items, including bread and pastries.

“We’re not trying for out-of-this world designs,” Irvin says. “The food shape will be practical to guarantee even cooking and efficient processing times. So pizza will look like pizza and biscuits like biscuits. We’re not planning for Michelin-star food—just healthy and nutritious meals.”

At Mars One, meanwhile, it’s been suggested that the colonists might recycle human waste to provide nutrients for their crops, and their diet might include insects and algae.

Plants might be used to produce oxygen as well. Dr Paul claims a bank of photosynthetic organisms (such as green algae) could be used for this task. Nasa also plans
to convert the carbon dioxide that dominates the thin Martian air into oxygen using MOXIE—a machine able to produce three-quarters of an ounce of oxygen an hour. If successful, a bigger device will launch two years before astronauts land on Mars, to produce oxygen for human respiration and for rocket fuel.

 

Physical and psychological impacts

Astronauts

Space travel comes with a health warning. Using the International Space Station (ISS) as a test bed, element scientist Professor Peter Norsk of Nasa’s Human Research programme has been investigating some of the physical challenges that astronauts will face. 

Our bodies work differently in space—even the way our blood flows. On Earth, gravity drags bodily fluids downwards, but in space this doesn’t happen, so the heart has to work harder to pump out more blood and more fluids cumulate in the head, putting extra pressure on the eyes. Russian cosmonauts place their bodies in low-pressure boxes to draw blood into the legs and wear bracelets around their thighs and upper arms so blood accumulates in the veins of the limbs. Nasa is currently testing the effectiveness of this.

Astronauts on ISS do two hours of daily aerobic, resistance and treadmill exercises to stave off the effects of weightlessness, which causes rapid bone and muscle wastage. Professor Norsk says the same countermeasure will be used on Mars, which has roughly one-third of the gravity of Earth. The use of the osteoporosis drug bisphosphonate to prevent bone-mass loss is another option, and artificial gravity is being tested using a centrifuge spinning device. 

Diet will also be important, and scientists are looking at foods that protect bone health and are rich in antioxidants to boost immunity. Space plays havoc with the immune system—blood-plasma samples taken from astronauts before and after a voyage show that some cells fail to kick in when needed, awakening latent viruses such as chicken pox, while others are over-active and cause allergy symptoms.

As well as physical challenges, the isolation, confinement and loss of privacy associated with long-duration space travel can provoke mental-health problems such as depression.

In March, American astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko will set off for a “One-Year Mission” on ISS, during which a host of psychological tests will take place to see how they cope mentally. Nasa is also trailing a Virtual Space Station, using a virtual-reality headset to send calming sounds, smells and images, and provide access to a virtual therapist and a self-administered depression-treatment programme. 

 

Technical challenges

Investigating the Orion's data after its successful test
Investigating the Orion's data after its successful test

The technical trials of reaching and inhabiting Mars are immense, but perhaps the greatest challenge is the threat posed by radiation. Astronauts who travel beyond low-Earth orbit are outside the protective shield of Earth’s atmosphere and magnetic field, exposing them to galactic cosmic rays that damage DNA and increase cancer risk. 

Nasa prohibits its astronauts from increasing their probability of dying from cancer by more than three per cent, but at least one expert has estimated that exposure to radiation on Mars could cut 15 to 24 years off an astronaut’s life. 

Nasa admits there’s “insufficient knowledge of the health effects of radiation, the space radiation environment and countermeasure efficacy” to recommend crew-exposure limits for extended lunar and Mars missions. 

The plan so far is to shield space vehicles and habitats to protect the humans inside. Orion has radiation sensors, and will use the mass already on board to maximise the amount of material (including equipment, supplies, launch and re-entry seats) that can be placed between the crew and the outside environment.

The Mars One living quarters will be covered with 16 feet of soil, to shield the inhabitants from cosmic rays. Their scientists say this will provide the same protection as the Earth’s atmosphere. 

 

Ethical issues

Mars, the new frontier

In June last year, the Committee on Human Spaceflight of the National Research Council, co-chaired by Jonathan Lunine, professor of planetary science at Cornell University, testifed before the US Congress that humans should continue exploring space, but funding would be needed for decades if we are to reach Mars. Such a programme, however, will cost hundreds of billions. Can the expense be justified? 

“No single rationale justifies a human spaceflight programme,” says Professor Lunine. “It’s the aggregate. Human spaceflight provides a broad set of benefits that, when taken together, makes a compelling case for such a programme.” 

Experts divide these benefits into practical and aspirational. Practical benefits are economic, educational and political. Space travel stimulates the aerospace industry and entices people into careers in science and engineering. And while space exploration is collaborative between countries (unlike the space race of the 20th century, which was dominated by the Cold War and the need for spaceflight supremacy), leading the financial and technical aspects of a space programme raises a country’s standing on the world stage.

Aspirational rationales, meanwhile, are described as “a shared human destiny and urge to explore”. And, ultimately, landing on Mars might be more aspirational than practical. While a human landing might happen in 35 to 50 years’ time, an entire self-sustaining colony could take centuries.”

“You can’t really quantify the value,” says Lunine. “But people are moved by aspirational rationales. If that wasn’t the case, everyone would study business and we’d have no philosophers or arts graduates to give colour and texture to existence.”

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