If humans ever settle on Mars, they will need water for drinking, growing food and maybe even making rocket fuel. There鈥檚 just one problem 鈥� the Red Planet doesn鈥檛 seem to have any accessible liquid water, only huge sheets of ice.
Luckily, we know how to drill ice for water. Such wells are already in operation in Antarctica, and now it seems it might be possible to get them working on Mars too.
In 2018, pictures from NASA鈥檚 Mars Reconnaissance Orbiter revealed eight cliffs of water ice covered in just a few metres of rock and dust. They are likely to be at least 130 metres thick, and there may be many more hidden underneath the Red Planet鈥檚 dusty surface.
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These sheets may be the best place on Mars for future explorers to get water. There is not enough water vapour in the atmosphere to be useful, the planet鈥檚 polar ice caps would be difficult for astronauts to reach, and once-promising signs of surface water flowing down hills may actually be dry sandslides.
Drill, baby, drill
There are cold areas on Earth where we need to drill down and melt ice for water as well. In the early 1960s, the US Army developed a type of reservoir called a Rodriguez well, or Rod well, for army camps in Greenland, and they have been used ever since in remote areas including the Amundsen鈥揝cott South Pole Station.
Stephen Hoffman at the Aerospace Corporation in Texas and his colleagues adapted simulations used to predict the performance of earthbound Rod wells to see .
A Rod well works by drilling through the ground into the ice, melting some of the ice to create a pool, and then pumping water back up from that pool. If you keep pumping heat into the pool, it creates a reservoir and a continuous water supply.
Hoffman and his team found that a Rod well on Mars could, in theory, produce about 380 litres of water per day and maintain a water reservoir of constant size at the bottom of the well by pumping in 9 kilowatts of power.
That鈥檚 close to the average daily water use per person in the US, but about 10 times what each astronaut on the International Space Station uses daily,聽because there is much less washing to do in space. It is plenty to support a few explorers on Mars鈥檚 surface, and extra equipment and more power could increase the water yield, Hoffman says.
Safety first
Still, the first missions will probably want to bring their own water, as there is no guarantee a Rod well would work, and the last thing you want is to get stranded on Mars with no water.
鈥淲e have the technology for Earth, but that doesn鈥檛 mean we have it for Mars,鈥� says Bruce Jakosky at the University of Colorado, Boulder. 鈥淚t鈥檚 a different environment in which it would need to operate, with a different ability of people to handle and operate equipment.鈥� This is similar to many other technologies we would need to maintain a human presence on Mars, he says, so it should not deter us from giving it a try.
There are other barriers we鈥檒l need to surpass before we can start drinking Martian well water. Ali Bramson at the University of Arizona聽says we don鈥檛 know the how pure the ice sheets are. We鈥檒l have to sample them first to determine what sort of processing they require to be safe to use and drink.
Nevertheless, Bramson says, 鈥淚 do think that drilling subsurface massive ice sheets is our best chance to be able to extract the quantities of water that will be needed to support humans on Mars鈥�.
