Imagine Earth in the future. Do you think we’ll have flying cars, floating cities or colonies deep under the ocean? Science fiction often paints an almost magical vision of the future. But what if we think more realistically?
By 2050 the UN predicts that Earth’s human population will have grown from 7.096 billion to between 8.3 and 10.9 billion. It will probably only continue to grow. In this version of the future, many questions will surround the sustainability of world populations, the growing pressures on the environment, global food supplies, and energy resources. Will Earth be able to sustain us? With the answer to this question unknown, humanity needs to start planning to leave the safety net of the Earth and look to the stars. Ok, Star Trek-style exploration maybe a bit too far into the future, but spreading out to one of our next door neighbours, such as the moon or Mars, is becoming a truly feasible option.
We have already started to pick out our Martian prime real estate through Curiosity and numerous orbiter and rover missions. Next month marks the one year anniversary of Nasa’s latest toy, the Mars Science Laboratory, better known as the Curiosity rover, landing on Mars. Although the moon is nearer, making access and communications easier, it is Mars that seems to have captured our imagination for a future human outpost. Much of this is inspired by evidence that it might have once been a world similar to the Earth.
Mars today, despite its sub-zero temperatures (on average -63C), thin non-breathable CO2-rich atmosphere, high UV-radiation and savage global dust storms, actually has the most clement environment in the solar system after the Earth. It also has the potential to contain habitable environments for life. To survive, terrestrial-type life needs an environment with a source of liquid water, organic molecules, and a source of energy.
One of the biggest problems we need to solve to enable humans to live on Mars is space agriculture. How can we expect to survive indefinitely on Mars without growing our own food, and producing our own water and oxygen? It costs $80,000 to ship four litres of water to the Moon! Just imagine the cost, let alone the logistics, of shipping water and food to Mars.
The first ‘Martians’ will therefore be two kinds — plants and humans — who are actually ideal companions. Humans consume oxygen and release carbon dioxide. Plants return the favour by consuming carbon dioxide and releasing oxygen. Humans can use edible parts of plants for nourishment, while human waste and inedible plant matter can (after being broken down by microbes in tanks called bioreactors) provide nutrients for plant growth. Plants such as asparagus, potatoes and marigolds have already been shown to grow in Mars-like soils, and seeds of radish, alfalfa, and mung bean have been observed to sprout in a CO2-rich atmosphere like that on Mars. Gardens are, in my opinion at least, the key to settling on Mars as they could help to recycle nutrients, provide drinking water and use the carbon from the toxic Martian atmospheric to produce oxygen through photosynthesis for humans to breathe. Gardens could even, in the long term, provide building materials such as wood and bamboo, and would improve the morale and wellbeing of the crew.
Plants on Mars would have to overcome the challenges that come with the planet having 38% of the gravity on Earth, a low pressure atmosphere, sub-zero temperatures, a lack of readily available liquid water and too much solar UV radiation. Any garden would therefore not be able to live freely on the surface but inside a greenhouse, commonly depicted as a geodesic dome, which would create a stable and comfortable environment for plant growth using all the natural resources Mars has to offer. There’ll be nothing to compensate for the reduced gravity on Mars. However, experiments on the International Space Station have shown that gravity doesn’t play as a great a role in plant growth as we once believed. It was always thought that the growth direction and patterns of roots were generated through a combination of a touch response between the root tip and whatever it is running into (a rock, a hard surface, etc.) and the force of gravity. Experiments on the ISS have shown that Arabidopsis — a mustard-like plant –- grows the same on Earth as in orbit. This research indicates that plants will be able to grow on Mars or the Moon as well as on the Earth (at least as far as gravity is concerned).
But research into space gardening won’t just help future Martians. With on-going climate change and increasing environmental problems here on Earth, studies into the logistics and physics of growing plants on the unfriendly surface of Mars, and the Moon, could help people to develop strategies to grow food in areas on the Earth which are not currently suitable for food production due to similarly hostile climates.
In five billion years, our Sun will start to die, expanding as it enters its red giant phase. It will engulf Venus, and, even if it doesn’t swell enough to reach Earth, it will still boil off the oceans and heat the surface to temperatures that even the hardiest life forms couldn’t survive. I hope that long before any of these natural or man-made terrestrial problems come to pass, we will choose to leave Earth and move to Mars, the moon or beyond, simply because we want to. When we do, we’ll have to take our trowels with us.
Image: How astronauts might grow their own food on Mars. Credit: Pat Rawlings/NASA