In July 2015, NASA’s New Horizons interplanetary space probe made its closest approach to the dwarf planet Pluto, having completed an eye-watering nine-year voyage of 4.8 billion kilometres. Pluto is so distant that it lies in the Kuiper Belt, a region of the Solar System beyond the eight major planets. This raises the possibility that space travel might one day be boundless.
For now, though, all eyes are on Mars, a 180-day journey away at best estimates and a possible target for a future human colony. And it isn’t merely science fiction – this space race has already begun.
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 spacecraft, 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. NASA’s Mars 2020 Rover will test an experimental weather station on Mars and MOXIE – 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 384,000 km away. This is small fry compared to the 55,000,000 km to Mars. Reaching the Red Planet will require serious hardware. NASA will use its new heavy-lift rocket, the Space Launch System (SLS), to propel Orion – its new generation spacecraft – into space. The SLS is more powerful than any previous rocket, with over 4 million kilograms of thrust at liftoff – more than 31 times the thrust of a Boeing 747. The computers running the software on Orion can process 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?
Humans will need self-sustaining water, food and oxygen to survive on Mars – and, ideally, on the voyage there as well. Farming in space isn’t easy. In microgravity, loose 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 gases, water and a growing substrate,” says Paul, who’s been studying the use of Arabidopsis thaliana (thale or mouse-ear cress) on the International Space Station (ISS). The crop is perfect for Mars missions, able to grow on a 10 cm 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 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 gases sink and light ones rise on Earth, but in space this doesn’t happen).
On Mars itself, the challenges will be different but equally complex. Extracting water locked up in ice will be crucial. 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. Mars One claims its astronauts will have 50 litres of recyclable water each per day. Then there is poor soil fertility, lack of beneficial bacteria and the weaker gravity – just 38% of Earth’s – that will make plant growth difficult.
While agriculture is being refined, food could 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. Dr David J. Irvin, director of SMRC, predicts that there will be 25 to 50 basic food items, including bread and pastries. “We’re not trying for out-of-this world designs,” he 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 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. 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 scaled-up model from the 2020 Rover version that will produce 22 kg of oxygen an hour for human respiration, as well as for rocket fuel.
Physical and mental impacts
Space travel comes with a health warning. Using the ISS as a test bed, element scientist Professor Peter Norsk of NASA’s Human Research programme has been investigating some of the many physical challenges facing astronauts.
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 and more fluids accumulate in the head, putting extra pressure on the eyes, which can lead to changes in vision that are often permanent. 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 this.
Astronauts on the ISS do an average of two hours of daily aerobic, resistance and treadmill exercises to stave off the effects of weightlessness, which causes rapid bone and muscle wastage. Norsk says similar countermeasures will be used on Mars. 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 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. American astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko underwent a host of psychological tests to see how they coped mentally during their ‘One-Year Mission’ on ISS, which ended in March this year. NASA is also testing interactive, multi-media programmes to manage psychosocial problems, such as calming virtual-reality headsets and self-administered treatment programmes.
Technical challenges
The technical trials of 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 3%, but at least one expert has estimated that exposure to radiation on Mars could cut 15 to 24 years off an astronaut’s life.
A 2008 NASA report 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 space 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 (such as equipment and supplies) to maximise the amount of material that can be placed between the crew and the outside environment.
The Mars One living quarters will be covered with 5 m of soil to shield the inhabitants from cosmic rays. This will provide the same protection as the Earth’s atmosphere, according to Mars One’s scientists.
Ethical issues
Decades of funding will be needed if we are to reach Mars. Such a programme will cost hundreds of billions. Can the expense be justified?
“No single rationale justifies a human spaceflight programme,” says Jonathan Lunine, professor of planetary science at Cornell University. “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 industry and entices people into careers in science and engineering. And while space exploration is collaborative between countries, 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 the surface of 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.”
